Fix RA assets installation from the Steam C&C:R version

Make yaml node resolving optional
Fix AutoTarget ignoring frozen actor bot targeting hack
2023-08-01 22:29:52 +03:00 · 2023-07-30 20:39:21 +02:00 · 2023-07-30 20:32:18 +02:00 · 2023-07-30 20:26:41 +02:00 · 2023-07-29 14:22:30 -05:00 · 2023-07-29 14:22:30 -05:00
2890 changed files with 121782 additions and 68962 deletions
--- a/.editorconfig
+++ b/.editorconfig
@@ -8,99 +8,915 @@ end_of_line = LF
 insert_final_newline = true
 trim_trailing_whitespace = true

+; 4-column tab indentation
+[*.yaml]
+indent_style = tab
+indent_size = 4
+
 ; 4-column tab indentation and .NET coding conventions
 [*.cs]
 indent_style = tab
 indent_size = 4

-dotnet_separate_import_directive_groups = false
-dotnet_sort_system_directives_first = true
+#### Code Style Rules
+#### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/

-csharp_style_var_elsewhere = true:suggestion
-csharp_style_var_for_built_in_types = true:suggestion
-csharp_style_var_when_type_is_apparent = true:suggestion
+# Severity Levels: https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/configuration-options#severity-level
+# Below we enable specific rules by setting severity to warning.
+# Rules are disabled by setting severity to silent (to still allow use in IDE) or none (to prevent all use).
+# Rules are listed below with any options available.
+# Options are commented out if they match the defaults.

-csharp_prefer_braces = when_multiline:suggestion
-csharp_using_directive_placement = outside_namespace:suggestion
-csharp_new_line_before_open_brace = all
-csharp_space_around_binary_operators = before_and_after
+### Language Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/language-rules

-#### Naming styles ####
+## this and Me preferences
+
+# IDE0003/IDE0009 Remove 'this' or 'Me' qualification/Add 'this' or 'Me' qualification
+#dotnet_style_qualification_for_field = false
+#dotnet_style_qualification_for_property = false
+#dotnet_style_qualification_for_method = false
+#dotnet_style_qualification_for_event = false
+dotnet_diagnostic.IDE0003.severity = warning
+dotnet_diagnostic.IDE0009.severity = warning
+
+## Use languages keywords for types
+
+# IDE0049 Use language keywords instead of framework type names for type references
+#dotnet_style_predefined_type_for_locals_parameters_members = true
+#dotnet_style_predefined_type_for_member_access = true
+dotnet_diagnostic.IDE0049.severity = warning
+
+## Modifier preferences
+
+# IDE0036 Order modifiers
+#csharp_preferred_modifier_order = public, private, protected, internal, file, static, extern, new, virtual, abstract, sealed, override, readonly, unsafe, required, volatile, async
+dotnet_diagnostic.IDE0036.severity = warning
+
+# IDE0040 Add accessibility modifiers
+dotnet_style_require_accessibility_modifiers = omit_if_default
+dotnet_diagnostic.IDE0040.severity = warning
+
+# IDE0044 Add readonly modifier
+#dotnet_style_readonly_field = true
+dotnet_diagnostic.IDE0044.severity = warning
+
+# IDE0062 Make local function static
+#csharp_prefer_static_local_function = true
+dotnet_diagnostic.IDE0062.severity = warning
+
+# IDE0064 Make struct fields writable
+# No options
+dotnet_diagnostic.IDE0064.severity = warning
+
+## Parentheses preferences
+
+# IDE0047/IDE0048 Remove unnecessary parentheses/Add parentheses for clarity
+dotnet_style_parentheses_in_arithmetic_binary_operators = never_if_unnecessary
+dotnet_style_parentheses_in_relational_binary_operators = never_if_unnecessary
+#dotnet_style_parentheses_in_other_binary_operators = always_for_clarity
+#dotnet_style_parentheses_in_other_operators = never_if_unnecessary
+dotnet_diagnostic.IDE0047.severity = warning
+dotnet_diagnostic.IDE0048.severity = warning
+
+## Expression-level preferences
+
+# IDE0010 Add missing cases to switch statement
+# No options
+dotnet_diagnostic.IDE0010.severity = silent
+
+# IDE0017 Use object initializers
+#dotnet_style_object_initializer = true
+dotnet_diagnostic.IDE0017.severity = warning
+
+# IDE0018 Inline variable declaration
+#csharp_style_inlined_variable_declaration = true
+dotnet_diagnostic.IDE0018.severity = warning
+
+# IDE0028 Use collection initializers
+#dotnet_style_collection_initializer = true
+dotnet_diagnostic.IDE0028.severity = warning
+
+# IDE0032 Use auto-implemented property
+#dotnet_style_prefer_auto_properties = true
+dotnet_diagnostic.IDE0032.severity = warning
+
+# IDE0033 Use explicitly provided tuple name
+#dotnet_style_explicit_tuple_names = true
+dotnet_diagnostic.IDE0033.severity = warning
+
+# IDE0034 Simplify 'default' expression
+#csharp_prefer_simple_default_expression = true
+dotnet_diagnostic.IDE0034.severity = warning
+
+# IDE0037 Use inferred member name
+#dotnet_style_prefer_inferred_tuple_names = true
+#dotnet_style_prefer_inferred_anonymous_type_member_names = true
+dotnet_diagnostic.IDE0037.severity = silent
+
+# IDE0039 Use local function instead of lambda
+#csharp_style_prefer_local_over_anonymous_function = true
+dotnet_diagnostic.IDE0039.severity = warning
+
+# IDE0042 Deconstruct variable declaration
+#csharp_style_deconstructed_variable_declaration = true
+dotnet_diagnostic.IDE0042.severity = warning
+
+# IDE0045 Use conditional expression for assignment
+#dotnet_style_prefer_conditional_expression_over_assignment = true
+dotnet_diagnostic.IDE0045.severity = silent
+
+# IDE0046 Use conditional expression for return
+#dotnet_style_prefer_conditional_expression_over_return = true
+dotnet_diagnostic.IDE0046.severity = silent
+
+# IDE0050 Convert anonymous type to tuple
+# No options
+dotnet_diagnostic.IDE0050.severity = silent
+
+# IDE0054/IDE0074 Use compound assignment/Use coalesce compound assignment
+#dotnet_style_prefer_compound_assignment = true
+dotnet_diagnostic.IDE0054.severity = warning
+dotnet_diagnostic.IDE0074.severity = warning
+
+# IDE0056 Use index operator
+#csharp_style_prefer_index_operator = true
+dotnet_diagnostic.IDE0056.severity = warning
+
+# IDE0057 Use range operator
+#csharp_style_prefer_range_operator = true
+dotnet_diagnostic.IDE0057.severity = warning
+
+# IDE0070 Use 'System.HashCode.Combine'
+# No options
+dotnet_diagnostic.IDE0070.severity = warning
+
+# IDE0071 Simplify interpolation
+#dotnet_style_prefer_simplified_interpolation = true
+dotnet_diagnostic.IDE0071.severity = warning
+
+# IDE0072 Add missing cases to switch expression
+# No options
+dotnet_diagnostic.IDE0072.severity = silent
+
+# IDE0075 Simplify conditional expression
+#dotnet_style_prefer_simplified_boolean_expressions = true
+dotnet_diagnostic.IDE0075.severity = warning
+
+# IDE0082 Convert 'typeof' to 'nameof'
+# No options
+dotnet_diagnostic.IDE0082.severity = warning
+
+# IDE0090 Simplify 'new' expression
+#csharp_style_implicit_object_creation_when_type_is_apparent = true
+dotnet_diagnostic.IDE0090.severity = warning
+
+# IDE0180 Use tuple to swap values
+#csharp_style_prefer_tuple_swap = true
+dotnet_diagnostic.IDE0180.severity = warning
+
+## Namespace declaration preferences
+
+# IDE0160/IDE0161 Use block-scoped namespace/Use file-scoped namespace
+#csharp_style_namespace_declarations = block_scoped
+dotnet_diagnostic.IDE0160.severity = warning
+dotnet_diagnostic.IDE0161.severity = warning
+
+## Null-checking preferences
+
+# IDE0016 Use throw expression
+#csharp_style_throw_expression = true
+dotnet_diagnostic.IDE0016.severity = silent
+
+# IDE0029/IDE0030/IDE0270 Use coalesce expression (non-nullable types)/Use coalesce expression (nullable types)/Use coalesce expression (if null)
+#dotnet_style_coalesce_expression = true
+dotnet_diagnostic.IDE0029.severity = warning
+dotnet_diagnostic.IDE0030.severity = warning
+dotnet_diagnostic.IDE0270.severity = silent
+
+# IDE0031 Use null propagation
+#dotnet_style_null_propagation = true
+dotnet_diagnostic.IDE0031.severity = warning
+
+# IDE0041 Use 'is null' check
+#dotnet_style_prefer_is_null_check_over_reference_equality_method = true
+dotnet_diagnostic.IDE0041.severity = warning
+
+# IDE0150 Prefer 'null' check over type check
+#csharp_style_prefer_null_check_over_type_check = true
+dotnet_diagnostic.IDE0150.severity = warning
+
+# IDE1005 Use conditional delegate call
+csharp_style_conditional_delegate_call = true # true is the default, but the rule is not triggered if this is not specified.
+dotnet_diagnostic.IDE1005.severity = warning
+
+## var preferences
+
+# IDE0007/IDE0008 Use 'var' instead of explicit type/Use explicit type instead of 'var'
+csharp_style_var_for_built_in_types = true
+csharp_style_var_when_type_is_apparent = true
+csharp_style_var_elsewhere = true
+dotnet_diagnostic.IDE0007.severity = warning
+dotnet_diagnostic.IDE0008.severity = warning
+
+## Expression-bodied-members
+
+# IDE0021 Use expression body for constructors
+#csharp_style_expression_bodied_constructors = false
+dotnet_diagnostic.IDE0021.severity = silent
+
+# IDE0022 Use expression body for methods
+#csharp_style_expression_bodied_methods = false
+dotnet_diagnostic.IDE0022.severity = silent
+
+# IDE0023/IDE0024 Use expression body for conversion operators/Use expression body for operators
+#csharp_style_expression_bodied_operators = false
+dotnet_diagnostic.IDE0023.severity = silent
+dotnet_diagnostic.IDE0024.severity = silent
+
+# IDE0025 Use expression body for properties
+#csharp_style_expression_bodied_properties = true
+dotnet_diagnostic.IDE0025.severity = silent
+
+# IDE0026 Use expression body for indexers
+#csharp_style_expression_bodied_indexers = true
+dotnet_diagnostic.IDE0026.severity = silent
+
+# IDE0027 Use expression body for accessors
+#csharp_style_expression_bodied_accessors = true
+dotnet_diagnostic.IDE0027.severity = warning
+
+# IDE0053 Use expression body for lambdas
+# This rule is buggy and not enforced for builds. ':warning' will at least enforce it in the IDE.
+csharp_style_expression_bodied_lambdas = when_on_single_line:warning
+dotnet_diagnostic.IDE0053.severity = warning
+
+# IDE0061 Use expression body for local functions
+csharp_style_expression_bodied_local_functions = when_on_single_line
+dotnet_diagnostic.IDE0061.severity = warning
+
+## Pattern matching preferences
+
+# IDE0019 Use pattern matching to avoid 'as' followed by a 'null' check
+#csharp_style_pattern_matching_over_as_with_null_check = true
+dotnet_diagnostic.IDE0019.severity = warning
+
+# IDE0020/IDE0038 Use pattern matching to avoid 'is' check followed by a cast (with variable)/Use pattern matching to avoid 'is' check followed by a cast (without variable)
+#csharp_style_pattern_matching_over_is_with_cast_check = true
+dotnet_diagnostic.IDE0020.severity = warning
+dotnet_diagnostic.IDE0038.severity = warning
+
+# IDE0066 Use switch expression
+#csharp_style_prefer_switch_expression = true
+dotnet_diagnostic.IDE0066.severity = silent
+
+# IDE0078 Use pattern matching
+#csharp_style_prefer_pattern_matching = true
+dotnet_diagnostic.IDE0078.severity = silent
+
+# IDE0083 Use pattern matching ('not' operator)
+#csharp_style_prefer_not_pattern = true
+dotnet_diagnostic.IDE0083.severity = warning
+
+# IDE0170 Simplify property pattern
+#csharp_style_prefer_extended_property_pattern = true
+dotnet_diagnostic.IDE0170.severity = silent # Requires C# 10
+
+## Code block preferences
+
+# IDE0011 Add braces
+#csharp_prefer_braces = true
+# No options match the style used in OpenRA.
+dotnet_diagnostic.IDE0011.severity = none
+
+# IDE0063 Use simple 'using' statement
+#csharp_prefer_simple_using_statement = true
+dotnet_diagnostic.IDE0063.severity = silent
+
+## 'using' directive preferences
+
+# IDE0065 'using' directive placement
+#csharp_using_directive_placement = outside_namespace
+dotnet_diagnostic.IDE0065.severity = silent
+
+## File header preferences
+
+# IDE0073 Require file header
+#file_header_template = unset
+# This rule does not allow us to enforce our desired header, as it prefixes the header lines with // comments, meaning we can't apply a region.
+dotnet_diagnostic.IDE0073.severity = none
+
+## Namespace naming preferences
+
+# IDE0130 Namespace does not match folder structure
+#dotnet_style_namespace_match_folder = true
+# This rule doesn't appear to work (never reports violations)
+dotnet_diagnostic.IDE0130.severity = none
+
+### Unnecessary Code Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/unnecessary-code-rules
+
+# IDE0001 Simplify name
+# No options
+dotnet_diagnostic.IDE0001.severity = warning
+
+# IDE0002 Simplify member access
+# No options
+dotnet_diagnostic.IDE0002.severity = warning
+
+# IDE0004 Remove unnecessary cast
+# No options
+dotnet_diagnostic.IDE0004.severity = warning
+
+# IDE0005 Remove unnecessary import
+# No options
+# IDE0005 is only enabled in the IDE by default. https://github.com/dotnet/roslyn/issues/41640
+# To enable it for builds outside the IDE the 'GenerateDocumentationFile' property must be enabled on the build.
+# GenerateDocumentationFile generates additional warnings about XML docs, so disable any we don't care about.
+dotnet_diagnostic.CS1591.severity = none # Missing XML comment for publicly visible type or member
+dotnet_diagnostic.IDE0005.severity = warning
+
+# IDE0035 Remove unreachable code
+# No options
+# Duplicates compiler warning CS0162
+dotnet_diagnostic.IDE0035.severity = none
+
+# IDE0051 Remove unused private member
+# No options
+dotnet_diagnostic.IDE0051.severity = warning
+
+# IDE0052 Remove unread private member
+# No options
+dotnet_diagnostic.IDE0052.severity = warning
+
+# IDE0058 Remove unnecessary expression value
+#csharp_style_unused_value_expression_statement_preference = discard_variable
+dotnet_diagnostic.IDE0058.severity = silent
+
+# IDE0059 Remove unnecessary value assignment
+#csharp_style_unused_value_assignment_preference = discard_variable
+dotnet_diagnostic.IDE0059.severity = warning
+
+# IDE0060 Remove unused parameter
+dotnet_code_quality_unused_parameters = non_public
+dotnet_diagnostic.IDE0060.severity = warning
+
+# IDE0079 Remove unnecessary suppression
+#dotnet_remove_unnecessary_suppression_exclusions = none
+dotnet_diagnostic.IDE0079.severity = warning
+
+# IDE0080 Remove unnecessary suppression operator
+# No options
+dotnet_diagnostic.IDE0080.severity = warning
+
+# IDE0100 Remove unnecessary equality operator
+# No options
+dotnet_diagnostic.IDE0100.severity = warning
+
+# IDE0110 Remove unnecessary discard
+# No options
+dotnet_diagnostic.IDE0110.severity = warning
+
+### Miscellaneous Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/miscellaneous-rules
+
+# IDE0076 Remove invalid global 'SuppressMessageAttribute'
+# No options
+dotnet_diagnostic.IDE0076.severity = warning
+
+# IDE0077 Avoid legacy format target in global 'SuppressMessageAttribute'
+# No options
+dotnet_diagnostic.IDE0077.severity = warning
+
+### Formatting Rules (IDE0055)
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/ide0055
+
+# We may eventually wish to enforce this rule, however some existing formatting conflicts with the rule despite being reasonable.
+# Additionally, the rule is buggy and likes to report spuriously after invoking Format Document in the IDE.
+dotnet_diagnostic.IDE0055.severity = none
+
+#dotnet_sort_system_directives_first = true
+#dotnet_separate_import_directive_groups = false
+#dotnet_style_namespace_match_folder = true
+
+#csharp_new_line_before_open_brace = all
+#csharp_new_line_before_else = true
+#csharp_new_line_before_catch = true
+#csharp_new_line_before_finally = true
+#csharp_new_line_before_members_in_object_initializers = true
+#csharp_new_line_before_members_in_anonymous_types = true
+#csharp_new_line_between_query_expression_clauses = true
+
+#csharp_indent_case_contents = true
+#csharp_indent_switch_labels = true
+#csharp_indent_labels = one_less_than_current
+#csharp_indent_block_contents = true
+#csharp_indent_braces = false
+#csharp_indent_case_contents_when_block = true
+
+#csharp_space_after_cast = false
+#csharp_space_after_keywords_in_control_flow_statements = true
+#csharp_space_between_parentheses =
+#csharp_space_before_colon_in_inheritance_clause = true
+#csharp_space_after_colon_in_inheritance_clause = true
+#csharp_space_around_binary_operators = before_and_after
+#csharp_space_between_method_declaration_parameter_list_parentheses = false
+#csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
+#csharp_space_between_method_declaration_name_and_open_parenthesis = false
+#csharp_space_between_method_call_parameter_list_parentheses = false
+#csharp_space_between_method_call_empty_parameter_list_parentheses = false
+#csharp_space_between_method_call_name_and_opening_parenthesis = false
+#csharp_space_after_comma = true
+#csharp_space_before_comma = false
+#csharp_space_after_dot = false
+#csharp_space_before_dot = false
+#csharp_space_after_semicolon_in_for_statement = true
+#csharp_space_before_semicolon_in_for_statement = false
+#csharp_space_around_declaration_statements = false
+#csharp_space_before_open_square_brackets = false
+#csharp_space_between_empty_square_brackets = false
+#csharp_space_between_square_brackets = false
+
+#csharp_preserve_single_line_statements = true
+#csharp_preserve_single_line_blocks = true
+
+
+### Naming Rules (IDE1006)
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/naming-rules
+dotnet_diagnostic.IDE1006.severity = warning
+
+## Naming styles

 dotnet_naming_style.camel_case.capitalization = camel_case

 dotnet_naming_style.pascal_case.capitalization = pascal_case

-# Symbol specifications
+dotnet_naming_style.i_prefix_pascal_case.capitalization = pascal_case
+dotnet_naming_style.i_prefix_pascal_case.required_prefix = I

-dotnet_naming_symbols.interface.applicable_kinds = interface
-dotnet_naming_symbols.interface.applicable_accessibilities = public, internal, private, protected, protected_internal
+## Naming Symbols

-dotnet_naming_symbols.const_private_field.applicable_kinds = field
-dotnet_naming_symbols.const_private_field.required_modifiers = const
-dotnet_naming_symbols.const_private_field.applicable_accessibilities = private
+dotnet_naming_symbols.const_locals.applicable_kinds = local
+dotnet_naming_symbols.const_locals.applicable_accessibilities = *
+dotnet_naming_symbols.const_locals.required_modifiers = const

-dotnet_naming_symbols.internal_field.applicable_kinds = field
-dotnet_naming_symbols.internal_field.applicable_accessibilities = internal
+dotnet_naming_symbols.const_fields.applicable_kinds = field
+dotnet_naming_symbols.const_fields.applicable_accessibilities = *
+dotnet_naming_symbols.const_fields.required_modifiers = const

-dotnet_naming_symbols.static_private_or_internal_field.required_modifiers = static
-dotnet_naming_symbols.static_private_or_internal_field.applicable_accessibilities = internal, private
+dotnet_naming_symbols.static_readonly_fields.applicable_kinds = field
+dotnet_naming_symbols.static_readonly_fields.applicable_accessibilities = *
+dotnet_naming_symbols.static_readonly_fields.required_modifiers = static, readonly

-dotnet_naming_symbols.private_or_internal_field.applicable_kinds = field
-dotnet_naming_symbols.private_or_internal_field.applicable_accessibilities = internal, private
+dotnet_naming_symbols.non_private_readonly_fields.applicable_kinds = field
+dotnet_naming_symbols.non_private_readonly_fields.applicable_accessibilities = public, internal, protected, protected_internal, private_protected
+dotnet_naming_symbols.non_private_readonly_fields.required_modifiers = readonly

-dotnet_naming_symbols.types.applicable_kinds = class, struct, interface, enum
-dotnet_naming_symbols.types.applicable_accessibilities = public, internal, private, protected, protected_internal
+dotnet_naming_symbols.private_or_protected_fields.applicable_kinds = field
+dotnet_naming_symbols.private_or_protected_fields.applicable_accessibilities = private, protected, private_protected

-dotnet_naming_symbols.non_field_members.applicable_kinds = property, event, method
-dotnet_naming_symbols.non_field_members.applicable_accessibilities = public, internal, private, protected, protected_internal
+dotnet_naming_symbols.interfaces.applicable_kinds = interface
+dotnet_naming_symbols.interfaces.applicable_accessibilities = *

-# Naming rules
+dotnet_naming_symbols.parameters_and_locals.applicable_kinds = parameter, local
+dotnet_naming_symbols.parameters_and_locals.applicable_accessibilities = *

-dotnet_naming_rule.non_field_members_should_be_pascal_case.severity = warning
-dotnet_naming_rule.non_field_members_should_be_pascal_case.symbols = non_field_members
-dotnet_naming_rule.non_field_members_should_be_pascal_case.style = pascal_case
+dotnet_naming_symbols.most_symbols.applicable_kinds = namespace, class, struct, enum, field, property, method, local_function, event, delegate, type_parameter
+dotnet_naming_symbols.most_symbols.applicable_accessibilities = *
+
+## Naming Rules
+
+dotnet_naming_rule.const_locals_should_be_pascal_case.symbols = const_locals
+dotnet_naming_rule.const_locals_should_be_pascal_case.style = pascal_case
+dotnet_naming_rule.const_locals_should_be_pascal_case.severity = warning
+
+dotnet_naming_rule.const_fields_should_be_pascal_case.symbols = const_fields
+dotnet_naming_rule.const_fields_should_be_pascal_case.style = pascal_case
+dotnet_naming_rule.const_fields_should_be_pascal_case.severity = warning
+
+dotnet_naming_rule.static_readonly_fields_should_be_pascal_case.symbols = static_readonly_fields
+dotnet_naming_rule.static_readonly_fields_should_be_pascal_case.style = pascal_case
+dotnet_naming_rule.static_readonly_fields_should_be_pascal_case.severity = warning
+
+dotnet_naming_rule.non_private_readonly_fields_should_be_pascal_case.symbols = non_private_readonly_fields
+dotnet_naming_rule.non_private_readonly_fields_should_be_pascal_case.style = pascal_case
+dotnet_naming_rule.non_private_readonly_fields_should_be_pascal_case.severity = warning
+
+dotnet_naming_rule.private_or_protected_fields_should_be_camel_case.symbols = private_or_protected_fields
+dotnet_naming_rule.private_or_protected_fields_should_be_camel_case.style = camel_case
+dotnet_naming_rule.private_or_protected_fields_should_be_camel_case.severity = warning
+
+dotnet_naming_rule.interfaces_should_be_i_prefix_pascal_case.symbols = interfaces
+dotnet_naming_rule.interfaces_should_be_i_prefix_pascal_case.style = i_prefix_pascal_case
+dotnet_naming_rule.interfaces_should_be_i_prefix_pascal_case.severity = warning
+
+dotnet_naming_rule.parameters_and_locals_should_be_camel_case.symbols = parameters_and_locals
+dotnet_naming_rule.parameters_and_locals_should_be_camel_case.style = camel_case
+dotnet_naming_rule.parameters_and_locals_should_be_camel_case.severity = warning
+
+dotnet_naming_rule.most_symbols_should_be_pascal_case.symbols = most_symbols
+dotnet_naming_rule.most_symbols_should_be_pascal_case.style = pascal_case
+dotnet_naming_rule.most_symbols_should_be_pascal_case.severity = warning


-dotnet_naming_rule.static_private_or_internal_field_should_be_pascal_case.severity = none
-dotnet_naming_rule.static_private_or_internal_field_should_be_pascal_case.symbols = static_private_or_internal_field
-dotnet_naming_rule.static_private_or_internal_field_should_be_pascal_case.style = pascal_case
+### StyleCop.Analyzers
+### https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/DOCUMENTATION.md

-dotnet_naming_rule.const_private_field_should_be_pascal_case.severity = warning
-dotnet_naming_rule.const_private_field_should_be_pascal_case.symbols = const_private_field
-dotnet_naming_rule.const_private_field_should_be_pascal_case.style = pascal_case
+# Below we enable rule categories by setting severity to warning.
+# We'll only list rules to disable.
+# Individual rules we wish to disable are typically set to none severity.

-dotnet_naming_rule.const_private_or_internal_field_should_be_pascal_case.severity = warning
-dotnet_naming_rule.const_private_or_internal_field_should_be_pascal_case.symbols = internal_field
-dotnet_naming_rule.const_private_or_internal_field_should_be_pascal_case.style = pascal_case
+# Covers SAxxxx and SXxxxx rules
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.DocumentationRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.LayoutRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.MaintainabilityRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.NamingRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.OrderingRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.ReadabilityRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.SpacingRules.severity = warning
+dotnet_analyzer_diagnostic.category-StyleCop.CSharp.SpecialRules.severity = warning

-dotnet_naming_rule.private_or_internal_field_should_be_camel_case.severity = warning
-dotnet_naming_rule.private_or_internal_field_should_be_camel_case.symbols = private_or_internal_field
-dotnet_naming_rule.private_or_internal_field_should_be_camel_case.style = camel_case
+# Rules that are covered by IDE0001 Simplify name
+dotnet_diagnostic.SA1125.severity = none # UseShorthandForNullableTypes

-# Naming rules
+# Rules that are covered by IDE0047 Remove unnecessary parentheses
+dotnet_diagnostic.SA1119.severity = none # StatementMustNotUseUnnecessaryParenthesis

-#require a space before the colon for bases or interfaces in a type declaration
-csharp_space_after_colon_in_inheritance_clause = true
-#require a space after a keyword in a control flow statement such as a for loop
-csharp_space_after_keywords_in_control_flow_statements = true
-#require a space before the colon for bases or interfaces in a type declaration
-csharp_space_before_colon_in_inheritance_clause = true
+# Rules that are covered by IDE0055 Formatting Rules
+dotnet_diagnostic.SA1027.severity = none # UseTabsCorrectly

-#Formatting - wrapping options
+# Rules that are covered by IDE1006 Naming Rules
+dotnet_diagnostic.SA1300.severity = none # ElementMustBeginWithUpperCaseLetter
+dotnet_diagnostic.SA1302.severity = none # InterfaceNamesMustBeginWithI
+dotnet_diagnostic.SA1303.severity = none # ConstFieldNamesMustBeginWithUpperCaseLetter
+dotnet_diagnostic.SA1304.severity = none # NonPrivateReadonlyFieldsMustBeginWithUpperCaseLetter
+dotnet_diagnostic.SA1306.severity = none # FieldNamesMustBeginWithLowerCaseLetter
+dotnet_diagnostic.SA1307.severity = none # AccessibleFieldsMustBeginWithUpperCaseLetter
+dotnet_diagnostic.SA1311.severity = none # StaticReadonlyFieldsMustBeginWithUpperCaseLetter
+dotnet_diagnostic.SA1312.severity = none # VariableNamesMustBeginWithLowerCaseLetter
+dotnet_diagnostic.SA1313.severity = none # ParameterNamesMustBeginWithLowerCaseLetter

-#leave code block on single line
-csharp_preserve_single_line_blocks = true
-#leave statements and member declarations on the same line
-csharp_preserve_single_line_statements = true
+# Rules that conflict with OpenRA project style conventions
+dotnet_diagnostic.SA1101.severity = none # PrefixLocalCallsWithThis
+dotnet_diagnostic.SA1107.severity = none # CodeMustNotContainMultipleStatementsOnOneLine
+dotnet_diagnostic.SA1116.severity = none # SplitParametersMustStartOnLineAfterDeclaration
+dotnet_diagnostic.SA1117.severity = none # ParametersMustBeOnSameLineOrSeparateLines
+dotnet_diagnostic.SA1118.severity = none # ParameterMustNotSpanMultipleLines
+dotnet_diagnostic.SA1122.severity = none # UseStringEmptyForEmptyStrings
+dotnet_diagnostic.SA1124.severity = none # DoNotUseRegions
+dotnet_diagnostic.SA1127.severity = none # GenericTypeConstraintsMustBeOnOwnLine
+dotnet_diagnostic.SA1132.severity = none # DoNotCombineFields
+dotnet_diagnostic.SA1135.severity = none # UsingDirectivesMustBeQualified
+dotnet_diagnostic.SA1136.severity = none # EnumValuesShouldBeOnSeparateLines
+dotnet_diagnostic.SA1200.severity = none # UsingDirectivesMustBePlacedCorrectly
+dotnet_diagnostic.SA1201.severity = none # ElementsMustAppearInTheCorrectOrder
+dotnet_diagnostic.SA1202.severity = none # ElementsMustBeOrderedByAccess
+dotnet_diagnostic.SA1204.severity = none # StaticElementsMustAppearBeforeInstanceElements
+dotnet_diagnostic.SA1214.severity = none # ReadonlyElementsMustAppearBeforeNonReadonlyElements
+dotnet_diagnostic.SX1309.severity = none # FieldNamesMustBeginWithUnderscore
+dotnet_diagnostic.SX1309S.severity = none # StaticFieldNamesMustBeginWithUnderscore
+dotnet_diagnostic.SA1314.severity = none # TypeParameterNamesMustBeginWithT
+dotnet_diagnostic.SA1400.severity = none # AccessModifierMustBeDeclared
+dotnet_diagnostic.SA1401.severity = none # FieldsMustBePrivate
+dotnet_diagnostic.SA1402.severity = none # FileMayOnlyContainASingleType
+dotnet_diagnostic.SA1407.severity = none # ArithmeticExpressionsMustDeclarePrecedence
+dotnet_diagnostic.SA1413.severity = none # UseTrailingCommasInMultiLineInitializers
+dotnet_diagnostic.SA1501.severity = none # StatementMustNotBeOnSingleLine
+dotnet_diagnostic.SA1502.severity = none # ElementMustNotBeOnSingleLine
+dotnet_diagnostic.SA1503.severity = none # BracesMustNotBeOmitted
+dotnet_diagnostic.SA1516.severity = none # ElementsMustBeSeparatedByBlankLine
+dotnet_diagnostic.SA1519.severity = none # BracesMustNotBeOmittedFromMultiLineChildStatement
+dotnet_diagnostic.SA1520.severity = none # UseBracesConsistently
+dotnet_diagnostic.SA1600.severity = none # ElementsMustBeDocumented
+dotnet_diagnostic.SA1601.severity = none # PartialElementsMustBeDocumented
+dotnet_diagnostic.SA1602.severity = none # EnumerationItemsMustBeDocumented
+dotnet_diagnostic.SA1611.severity = none # ElementParametersShouldBeDocumented
+dotnet_diagnostic.SA1615.severity = none # ElementReturnValueShouldBeDocumented
+dotnet_diagnostic.SA1618.severity = none # GenericTypeParametersShouldBeDocumented
+dotnet_diagnostic.SA1623.severity = none # PropertySummaryDocumentationShouldMatchAccessors
+dotnet_diagnostic.SA1633.severity = none # FileMustHaveHeader
+dotnet_diagnostic.SA1642.severity = none # ConstructorSummaryDocumentationShouldBeginWithStandardText
+dotnet_diagnostic.SA1649.severity = none # FileNameMustMatchTypeName

-#prefer the language keyword for member access expressions, instead of the type name, for types that have a keyword to represent them
-dotnet_style_predefined_type_for_member_access = true:suggestion
+#### Code Quality Rules
+#### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/

-#prefer the language keyword for local variables, method parameters, and class members, instead of the type name, for types that have a keyword to represent them
-dotnet_style_predefined_type_for_locals_parameters_members = true:suggestion
+# Below we enable specific rules by setting severity to warning.
+# Rules are listed below with any options available.
+# Options are commented out if they match the defaults.

-; 4-column tab indentation
-[*.yaml]
-indent_style = tab
-indent_size = 4
+# Rule options that apply over multiple rules are set here.
+# https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/code-quality-rule-options
+dotnet_code_quality.api_surface = all
+
+### Design Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/design-warnings
+
+# Collections should implement generic interface.
+#dotnet_code_quality.CA1010.additional_required_generic_interfaces =
+dotnet_diagnostic.CA1010.severity = warning
+
+# Abstract types should not have public constructors.
+dotnet_diagnostic.CA1012.severity = warning
+
+# Mark attributes with 'AttributeUsageAttribute'.
+dotnet_diagnostic.CA1018.severity = warning
+
+# Override methods on comparable types.
+dotnet_diagnostic.CA1036.severity = warning
+
+# Provide ObsoleteAttribute message.
+dotnet_diagnostic.CA1041.severity = warning
+
+# Do not declare protected members in sealed types.
+dotnet_diagnostic.CA1047.severity = warning
+
+# Declare types in namespaces.
+dotnet_diagnostic.CA1050.severity = warning
+
+# Static holder types should be 'Static' or 'NotInheritable'.
+dotnet_diagnostic.CA1052.severity = warning
+
+# Do not hide base class methods.
+dotnet_diagnostic.CA1061.severity = warning
+
+# Exceptions should be public.
+dotnet_diagnostic.CA1064.severity = warning
+
+# Implement 'IEquatable' when overriding 'Equals'.
+dotnet_diagnostic.CA1066.severity = warning
+
+# Override 'Equals' when implementing 'IEquatable'.
+dotnet_diagnostic.CA1067.severity = warning
+
+# 'CancellationToken' parameters must come last.
+dotnet_diagnostic.CA1068.severity = warning
+
+# Do not declare event fields as virtual.
+dotnet_diagnostic.CA1070.severity = warning
+
+### Documentation Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/documentation-warnings
+
+# Avoid using 'cref' tags with a prefix.
+dotnet_diagnostic.CA1200.severity = warning
+
+### Globalization Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/globalization-warnings
+
+### Portability and Interoperability Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/interoperability-warnings
+
+# Do not use 'OutAttribute' on string parameters for P/Invokes.
+dotnet_diagnostic.CA1417.severity = warning
+
+### Maintainability Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/maintainability-warnings
+
+# Use 'nameof' in place of string.
+dotnet_diagnostic.CA1507.severity = warning
+
+### Naming Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/naming-warnings
+
+# Do not prefix enum values with type name.
+dotnet_code_quality.CA1712.enum_values_prefix_trigger = AnyEnumValue
+dotnet_diagnostic.CA1712.severity = warning
+
+# Flags enums should have plural names.
+dotnet_diagnostic.CA1714.severity = warning
+
+# Only 'FlagsAttribute' enums should have plural names.
+dotnet_diagnostic.CA1717.severity = warning
+
+### Performance Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/performance-warnings
+
+# Use Literals Where Appropriate.
+#dotnet_code_quality.CA1802.required_modifiers = static
+dotnet_diagnostic.CA1802.severity = warning
+
+# Remove empty finalizers.
+dotnet_diagnostic.CA1821.severity = warning
+
+# Mark members as static.
+dotnet_code_quality.CA1822.api_surface = private,internal
+dotnet_diagnostic.CA1822.severity = warning
+
+# Avoid unused private fields.
+dotnet_diagnostic.CA1823.severity = warning
+
+# Avoid zero-length array allocations.
+dotnet_diagnostic.CA1825.severity = warning
+
+# Use property instead of Linq Enumerable method.
+#dotnet_code_quality.CA1826.exclude_ordefault_methods = false
+dotnet_diagnostic.CA1826.severity = warning
+
+# Do not use Count/LongCount when Any can be used.
+dotnet_diagnostic.CA1827.severity = warning
+
+# Do not use CountAsync/LongCountAsync when AnyAsync can be used.
+dotnet_diagnostic.CA1828.severity = warning
+
+# Use Length/Count property instead of Enumerable.Count method.
+dotnet_diagnostic.CA1829.severity = warning
+
+# Prefer strongly-typed Append and Insert method overloads on StringBuilder.
+dotnet_diagnostic.CA1830.severity = warning
+
+# Use AsSpan instead of Range-based indexers for string when appropriate.
+dotnet_diagnostic.CA1831.severity = warning
+
+# Use AsSpan or AsMemory instead of Range-based indexers for getting ReadOnlySpan or ReadOnlyMemory portion of an array.
+dotnet_diagnostic.CA1832.severity = warning
+
+# Use AsSpan or AsMemory instead of Range-based indexers for getting Span or Memory portion of an array.
+dotnet_diagnostic.CA1833.severity = warning
+
+# Use StringBuilder.Append(char) for single character strings.
+dotnet_diagnostic.CA1834.severity = warning
+
+# Prefer the memory-based overloads of ReadAsync/WriteAsync methods in stream-based classes.
+dotnet_diagnostic.CA1835.severity = warning
+
+# Prefer IsEmpty over Count when available.
+dotnet_diagnostic.CA1836.severity = warning
+
+# Use Environment.ProcessId instead of Process.GetCurrentProcess().Id.
+dotnet_diagnostic.CA1837.severity = warning
+
+# Avoid StringBuilder parameters for P/Invokes.
+dotnet_diagnostic.CA1838.severity = warning
+
+# Use Environment.ProcessPath instead of Process.GetCurrentProcess().MainModule.FileName.
+dotnet_diagnostic.CA1839.severity = warning
+
+# Use Environment.CurrentManagedThreadId instead of Thread.CurrentThread.ManagedThreadId.
+dotnet_diagnostic.CA1840.severity = warning
+
+# Prefer Dictionary Contains methods.
+dotnet_diagnostic.CA1841.severity = warning
+
+# Do not use 'WhenAll' with a single task.
+dotnet_diagnostic.CA1842.severity = warning
+
+# Do not use 'WaitAll' with a single task.
+dotnet_diagnostic.CA1843.severity = warning
+
+# Provide memory-based overrides of async methods when subclassing 'Stream'.
+dotnet_diagnostic.CA1844.severity = warning
+
+# Use span-based 'string.Concat'. (Not available on mono)
+dotnet_diagnostic.CA1845.severity = none
+
+# Prefer AsSpan over Substring.
+dotnet_diagnostic.CA1846.severity = warning
+
+# Use string.Contains(char) instead of string.Contains(string) with single characters.
+dotnet_diagnostic.CA1847.severity = warning
+
+# Call async methods when in an async method.
+dotnet_diagnostic.CA1849.severity = warning
+
+# Prefer static HashData method over ComputeHash. (Not available on mono)
+dotnet_diagnostic.CA1850.severity = none
+
+# Seal internal types.
+dotnet_diagnostic.CA1852.severity = warning
+
+# Unnecessary call to 'Dictionary.ContainsKey(key)'.
+dotnet_diagnostic.CA1853.severity = warning
+
+# Prefer the IDictionary.TryGetValue(TKey, out TValue) method.
+dotnet_diagnostic.CA1854.severity = warning
+
+# Use Span<T>.Clear() instead of Span<T>.Fill().
+dotnet_diagnostic.CA1855.severity = warning
+
+# Use StartsWith instead of IndexOf.
+dotnet_diagnostic.CA1858.severity = warning
+
+# Avoid using 'Enumerable.Any()' extension method.
+dotnet_diagnostic.CA1860.severity = warning
+
+### Reliability Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/reliability-warnings
+
+# Do not assign property within its setter.
+dotnet_diagnostic.CA2011.severity = warning
+
+# Use ValueTasks correctly.
+dotnet_diagnostic.CA2012.severity = warning
+
+# Do not use ReferenceEquals with value types.
+dotnet_diagnostic.CA2013.severity = warning
+
+# Do not use stackalloc in loops.
+dotnet_diagnostic.CA2014.severity = warning
+
+# Forward the CancellationToken parameter to methods that take one.
+dotnet_diagnostic.CA2016.severity = warning
+
+# The 'count' argument to Buffer.BlockCopy should specify the number of bytes to copy.
+dotnet_diagnostic.CA2018.severity = warning
+
+# ThreadStatic fields should not use inline initialization.
+dotnet_diagnostic.CA2019.severity = warning
+
+### Security Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/security-warnings
+
+# Do Not Use Broken Cryptographic Algorithms.
+dotnet_diagnostic.CA5351.severity = warning
+
+### Usage Rules
+### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/usage-warnings
+
+# Call GC.SuppressFinalize correctly.
+dotnet_diagnostic.CA1816.severity = warning
+
+# Rethrow to preserve stack details.
+dotnet_diagnostic.CA2200.severity = warning
+
+# Initialize value type static fields inline.
+dotnet_diagnostic.CA2207.severity = warning
+
+# Instantiate argument exceptions correctly.
+dotnet_diagnostic.CA2208.severity = warning
+
+# Dispose methods should call base class dispose.
+dotnet_diagnostic.CA2215.severity = warning
+
+# Disposable types should declare finalizer.
+dotnet_diagnostic.CA2216.severity = warning
+
+# Override GetHashCode on overriding Equals.
+dotnet_diagnostic.CA2218.severity = warning
+
+# Overload operator equals on overriding ValueType.Equals.
+dotnet_diagnostic.CA2231.severity = warning
+
+# Provide correct arguments to formatting methods.
+#dotnet_code_quality.CA2241.additional_string_formatting_methods =
+dotnet_code_quality.CA2241.try_determine_additional_string_formatting_methods_automatically = true
+dotnet_diagnostic.CA2241.severity = warning
+
+# Test for NaN correctly.
+dotnet_diagnostic.CA2242.severity = warning
+
+# Attribute string literals should parse correctly.
+dotnet_diagnostic.CA2243.severity = warning
+
+# Do not duplicate indexed element initializations.
+dotnet_diagnostic.CA2244.severity = warning
+
+# Do not assign a property to itself.
+dotnet_diagnostic.CA2245.severity = warning
+
+# Argument passed to TaskCompletionSource constructor should be TaskCreationOptions enum instead of TaskContinuationOptions enum.
+dotnet_diagnostic.CA2247.severity = warning
+
+# Provide correct enum argument to Enum.HasFlag.
+dotnet_diagnostic.CA2248.severity = warning
+
+# Use ThrowIfCancellationRequested.
+dotnet_diagnostic.CA2250.severity = warning
+
+# Ensure ThreadStatic is only used with static fields.
+dotnet_diagnostic.CA2259.severity = warning
+
+### Roslynator
+### https://github.com/JosefPihrt/Roslynator/tree/main/docs/analyzers
+
+# Below we enable specific rules by setting severity to warning.
+
+# Use 'Count' property instead of 'Any' method.
+dotnet_diagnostic.RCS1080.severity = warning
+
+# Use read-only auto-implemented property.
+dotnet_diagnostic.RCS1170.severity = warning
+
+# Unnecessary interpolated string.
+dotnet_diagnostic.RCS1214.severity = warning
+
+# Unnecessary usage of verbatim string literal.
+dotnet_diagnostic.RCS1192.severity = warning
+
+# Use pattern matching instead of combination of 'as' operator and null check.
+dotnet_diagnostic.RCS1221.severity = warning
+
+# Expression is always equal to 'true'.
+dotnet_diagnostic.RCS1215.severity = warning
+
+# Use StringComparison when comparing strings.
+dotnet_diagnostic.RCS1155.severity = warning
+
+# Abstract type should not have public constructors.
+dotnet_diagnostic.RCS1160.severity = warning
+
+# Optimize 'Dictionary<TKey, TValue>.ContainsKey' call.
+dotnet_diagnostic.RCS1235.severity = warning
+
+# Call extension method as instance method.
+dotnet_diagnostic.RCS1196.severity = warning
--- a/.github/ISSUE_TEMPLATE/config.yml
+++ b/.github/ISSUE_TEMPLATE/config.yml
@@ -10,5 +10,5 @@ contact_links:
    url: https://discord.openra.net/
    about: Join the community Discord server for community discussion and support.
  - name: OpenRA IRC Channel
-    url: https://webchat.freenode.net/#openra
-    about: Join our development IRC channel on freenode for discussion of development topics.
+    url: https://web.libera.chat/#openra
+    about: Join our development IRC channel on Libera for discussion of development topics.
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -13,4 +13,4 @@ You can help speed up the review process by following a few steps:
 * Respond to review comments as soon as you reasonably can.  Reviewers will usually prioritize Pull Requests that are still fresh in their minds.  Make sure to leave a comment when you push new changes, otherwise GitHub does not automatically notify reviewers!
 * Leave a polite comment asking for reviews if a week or more has passed without feedback.

-If you need any help you can ask in the #openra IRC channel on freenode (most active during European evenings).
+If you need any help you can ask on Discord (https://discord.openra.net) or in the #openra IRC channel on Libera (not as active as Discord).
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -1,48 +0,0 @@
-name: Continuous Integration
-
-on:
-  push:
-  pull_request:
-    branches: [ bleed ]
-
-jobs:
-  linux-mono:
-    name: Linux (mono)
-    runs-on: ubuntu-20.04
-
-    steps:
-      - name: Clone Repository
-        uses: actions/checkout@v2
-
-      - name: Check Code
-        run: |
-          mono --version
-          make check
-          mono ~/.nuget/packages/nunit.consolerunner/3.11.1/tools/nunit3-console.exe --noresult bin/OpenRA.Test.dll
-
-      - name: Check Mods
-        run: |
-          sudo apt-get install lua5.1
-          make check-scripts
-          make test
-
-  windows:
-    name: Windows (Framework 4.7)
-    runs-on: windows-2019
-
-    steps:
-      - name: Clone Repository
-        uses: actions/checkout@v2
-
-      - name: Check Code
-        shell: powershell
-        run: |
-          .\make.ps1 check
-          Invoke-Expression "$home\.nuget\packages\nunit.consolerunner\3.11.1\tools\nunit3-console.exe --noresult bin/OpenRA.Test.dll"
-
-      - name: Check Mods
-        run: |
-          chocolatey install lua --version 5.1.5.52
-          $ENV:Path = $ENV:Path + ";C:\Program Files (x86)\Lua\5.1\"
-          .\make.ps1 check-scripts
-          .\make.ps1 test
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,81 @@
+name: Continuous Integration
+
+on:
+  push:
+  pull_request:
+    branches: [ bleed, 'prep-*' ]
+
+permissions:
+  contents: read  #  to fetch code (actions/checkout)
+
+jobs:
+  linux:
+    name: Linux (.NET 6.0)
+    runs-on: ubuntu-22.04
+
+    steps:
+      - name: Clone Repository
+        uses: actions/checkout@v3
+
+      - name: Install .NET 6.0
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'
+
+      - name: Check Code
+        run: |
+          make check
+          make tests
+
+      - name: Check Mods
+        run: |
+          sudo apt-get install lua5.1
+          make check-scripts
+          make TREAT_WARNINGS_AS_ERRORS=true test
+
+  linux-mono:
+    name: Linux (mono)
+    runs-on: ubuntu-22.04
+
+    steps:
+      - name: Clone Repository
+        uses: actions/checkout@v3
+
+      - name: Check Code
+        run: |
+          mono --version
+          make RUNTIME=mono check
+
+      - name: Check Mods
+        run: |
+          # check-scripts does not depend on .net/mono, so is not needed here
+          make RUNTIME=mono TREAT_WARNINGS_AS_ERRORS=true test
+
+  windows:
+    name: Windows (.NET 6.0)
+    runs-on: windows-2019
+
+    steps:
+      - name: Clone Repository
+        uses: actions/checkout@v3
+
+      - name: Install .NET 6.0
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'
+
+      - name: Check Code
+        shell: powershell
+        run: |
+          # Work around runtime failures on the GH Actions runner
+          dotnet nuget add source https://api.nuget.org/v3/index.json -n nuget.org
+          .\make.ps1 check
+          .\make.ps1 tests
+
+      - name: Check Mods
+        run: |
+          choco install lua --version 5.1.5.52
+          $ENV:Path = $ENV:Path + ";C:\Program Files (x86)\Lua\5.1\"
+          $ENV:TREAT_WARNINGS_AS_ERRORS = "true"
+          .\make.ps1 check-scripts
+          .\make.ps1 test
--- a/.github/workflows/documentation.yml
+++ b/.github/workflows/documentation.yml
@@ -8,23 +8,31 @@ on:
        required: true
        default: 'release-xxxxxxxx'

+permissions:
+  contents: read  #  to fetch code (actions/checkout)
+
 jobs:
  wiki:
    name: Update Wiki
    if: github.repository == 'openra/openra'
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
    steps:
      - name: Clone Repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
        with:
          ref: ${{ github.event.inputs.tag }}

+      - name: Install .NET 6
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'
+
      - name: Prepare Environment
        run: |
          make all

      - name: Clone Wiki
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
        with:
          repository: openra/openra.wiki
          token: ${{ secrets.DOCS_TOKEN }}
@@ -58,42 +66,78 @@ jobs:
  docs:
    name: Update docs.openra.net
    if: github.repository == 'openra/openra'
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
    steps:
-      - name: Clone docs.openra.net
-        uses: actions/checkout@v2
+      - name: Clone Repository
+        uses: actions/checkout@v3
        with:
-          repository: openra/docs.git
+          ref: ${{ github.event.inputs.tag }}
+
+      - name: Install .NET 6
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'
+
+      - name: Prepare Environment
+        run: |
+          make all
+
+      - name: Clone docs.openra.net (Playtest)
+        if: startsWith(github.event.inputs.tag, 'playtest-')
+        uses: actions/checkout@v3
+        with:
+          repository: openra/docs
          token: ${{ secrets.DOCS_TOKEN }}
          path: docs
-          ref: ${{ github.event.inputs.tag }}
+          ref: playtest
+
+      - name: Clone docs.openra.net (Release)
+        if: startsWith(github.event.inputs.tag, 'release-')
+        uses: actions/checkout@v3
+        with:
+          repository: openra/docs
+          token: ${{ secrets.DOCS_TOKEN }}
+          path: docs
+          ref: release

      - name: Update docs.openra.net (Playtest)
        if: startsWith(github.event.inputs.tag, 'playtest-')
        env:
          GIT_TAG: ${{ github.event.inputs.tag }}
        run: |
-          ./utility.sh all --docs "${GIT_TAG}" > "docs/playtest/traits.md"
-          ./utility.sh all --weapon-docs "${GIT_TAG}" > "docs/playtest/weapons.md"
-          ./utility.sh all --lua-docs "${GIT_TAG}" > "docs/playtest/lua.md"
+          ./utility.sh all --docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/traits.md"
+          ./utility.sh all --weapon-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/weapons.md"
+          ./utility.sh all --sprite-sequence-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/sprite-sequences.md"
+          ./utility.sh all --lua-docs "${GIT_TAG}" > "docs/api/lua.md"

      - name: Update docs.openra.net (Release)
        if: startsWith(github.event.inputs.tag, 'release-')
        env:
          GIT_TAG: ${{ github.event.inputs.tag }}
        run: |
-          ./utility.sh all --docs "${GIT_TAG}" > "docs/release/traits.md"
-          ./utility.sh all --weapon-docs "${GIT_TAG}" > "docs/release/weapons.md"
-          ./utility.sh all --lua-docs "${GIT_TAG}" > "docs/release/lua.md"
+          ./utility.sh all --docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/traits.md"
+          ./utility.sh all --weapon-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/weapons.md"
+          ./utility.sh all --sprite-sequence-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/sprite-sequences.md"
+          ./utility.sh all --lua-docs "${GIT_TAG}" > "docs/api/lua.md"

-      - name: Push docs.openra.net
+      - name: Commit docs.openra.net
        env:
          GIT_TAG: ${{ github.event.inputs.tag }}
        run: |
          cd docs
          git config --local user.email "actions@github.com"
          git config --local user.name "GitHub Actions"
-          git add --all
+          git add api/*.md
          git commit -m "Update auto-generated documentation for ${GIT_TAG}"
-          git push origin master

+      - name: Push docs.openra.net (Release)
+        if: startsWith(github.event.inputs.tag, 'release-')
+        run: |
+          cd docs
+          git push origin release
+
+      - name: Push docs.openra.net (Playtest)
+        if: startsWith(github.event.inputs.tag, 'playtest-')
+        run: |
+          cd docs
+          git push origin playtest
--- a/.github/workflows/itch.yml
+++ b/.github/workflows/itch.yml
@@ -8,24 +8,23 @@ on:
        required: true
        default: 'release-xxxxxxxx'

+permissions: {}
 jobs:
  itch:
    name: Deploy to itch.io
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
    if: github.repository == 'openra/openra'
    steps:
      - name: Download Packages
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
        run: |
-          wget -q "https://github.com/${{ github.repository }}/releases/download/${GIT_TAG}/OpenRA-${GIT_TAG}-x64.exe"
-          wget -q "https://github.com/${{ github.repository }}/releases/download/${GIT_TAG}/OpenRA-${GIT_TAG}-x64-winportable.zip" -O "OpenRA-${GIT_TAG}-x64-win-itch.zip"
-          wget -q "https://github.com${{ github.repository }}/releases/download/${GIT_TAG}/OpenRA-${GIT_TAG}.dmg"
-          wget -q "https://github.com/${{ github.repository }}/releases/download/${GIT_TAG}/OpenRA-Dune-2000-x86_64.AppImage"
-          wget -q "https://github.com/${{ github.repository }}/releases/download/${GIT_TAG}/OpenRA-Red-Alert-x86_64.AppImage"
-          wget -q "https://github.com/${{ github.repository }}/releases/download/${GIT_TAG}/OpenRA-Tiberian-Dawn-x86_64.AppImage"
-          wget -q "https://raw.githubusercontent.com/${{ github.repository }}/${GIT_TAG}/packaging/.itch.toml"
-          zip -u "OpenRA-${GIT_TAG}-x64-win-itch.zip" .itch.toml
+          wget -q "https://github.com/${{ github.repository }}/releases/download/${{ github.event.inputs.tag }}/OpenRA-${{ github.event.inputs.tag }}-x64.exe"
+          wget -q "https://github.com/${{ github.repository }}/releases/download/${{ github.event.inputs.tag }}/OpenRA-${{ github.event.inputs.tag }}-x64-winportable.zip" -O "OpenRA-${{ github.event.inputs.tag }}-x64-win-itch.zip"
+          wget -q "https://github.com/${{ github.repository }}/releases/download/${{ github.event.inputs.tag }}/OpenRA-${{ github.event.inputs.tag }}.dmg"
+          wget -q "https://github.com/${{ github.repository }}/releases/download/${{ github.event.inputs.tag }}/OpenRA-Dune-2000-x86_64.AppImage"
+          wget -q "https://github.com/${{ github.repository }}/releases/download/${{ github.event.inputs.tag }}/OpenRA-Red-Alert-x86_64.AppImage"
+          wget -q "https://github.com/${{ github.repository }}/releases/download/${{ github.event.inputs.tag }}/OpenRA-Tiberian-Dawn-x86_64.AppImage"
+          wget -q "https://raw.githubusercontent.com/${{ github.repository }}/${{ github.event.inputs.tag }}/packaging/.itch.toml"
+          zip -u "OpenRA-${{ github.event.inputs.tag }}-x64-win-itch.zip" .itch.toml

      - name: Publish Windows Installer
        uses: josephbmanley/butler-publish-itchio-action@master
@@ -33,9 +32,9 @@ jobs:
          BUTLER_CREDENTIALS: ${{ secrets.BUTLER_CREDENTIALS }}
          CHANNEL: win
          ITCH_GAME: openra
-          ITCH_USER: openra-developers
+          ITCH_USER: openra
          VERSION: ${{ github.event.inputs.tag }}
-          PACKAGE: OpenRA-${{ github.event.inputs.tag }}}-x64.exe"
+          PACKAGE: OpenRA-${{ github.event.inputs.tag }}-x64.exe

      - name: Publish Windows Itch Bundle
        uses: josephbmanley/butler-publish-itchio-action@master
@@ -43,7 +42,7 @@ jobs:
          BUTLER_CREDENTIALS: ${{ secrets.BUTLER_CREDENTIALS }}
          CHANNEL: itch
          ITCH_GAME: openra
-          ITCH_USER: openra-developers
+          ITCH_USER: openra
          VERSION: ${{ github.event.inputs.tag }}
          PACKAGE: OpenRA-${{ github.event.inputs.tag }}-x64-win-itch.zip

@@ -53,9 +52,9 @@ jobs:
          BUTLER_CREDENTIALS: ${{ secrets.BUTLER_CREDENTIALS }}
          CHANNEL: macos
          ITCH_GAME: openra
-          ITCH_USER: openra-developers
+          ITCH_USER: openra
          VERSION: ${{ github.event.inputs.tag }}
-          PACKAGE: OpenRA-${{ github.event.inputs.tag }}}.dmg"
+          PACKAGE: OpenRA-${{ github.event.inputs.tag }}.dmg

      - name: Publish RA AppImage
        uses: josephbmanley/butler-publish-itchio-action@master
@@ -63,7 +62,7 @@ jobs:
          BUTLER_CREDENTIALS: ${{ secrets.BUTLER_CREDENTIALS }}
          CHANNEL: linux-ra
          ITCH_GAME: openra
-          ITCH_USER: openra-developers
+          ITCH_USER: openra
          VERSION: ${{ github.event.inputs.tag }}
          PACKAGE: OpenRA-Red-Alert-x86_64.AppImage

@@ -73,7 +72,7 @@ jobs:
          BUTLER_CREDENTIALS: ${{ secrets.BUTLER_CREDENTIALS }}
          CHANNEL: linux-cnc
          ITCH_GAME: openra
-          ITCH_USER: openra-developers
+          ITCH_USER: openra
          VERSION: ${{ github.event.inputs.tag }}
          PACKAGE: OpenRA-Tiberian-Dawn-x86_64.AppImage

@@ -83,6 +82,6 @@ jobs:
          BUTLER_CREDENTIALS: ${{ secrets.BUTLER_CREDENTIALS }}
          CHANNEL: linux-d2k
          ITCH_GAME: openra
-          ITCH_USER: openra-developers
+          ITCH_USER: openra
          VERSION: ${{ github.event.inputs.tag }}
          PACKAGE: OpenRA-Dune-2000-x86_64.AppImage
--- a/.github/workflows/packaging.yml
+++ b/.github/workflows/packaging.yml
@@ -7,13 +7,45 @@ on:
    - 'playtest-*'
    - 'devtest-*'

+permissions:
+  contents: write  #  for release creation (svenstaro/upload-release-action)
+
 jobs:
-  linux:
-    name: Linux AppImages
-    runs-on: ubuntu-20.04
+  source:
+    name: Source Tarball
+    runs-on: ubuntu-22.04
    steps:
      - name: Clone Repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
+
+      - name: Prepare Environment
+        run: echo "GIT_TAG=${GITHUB_REF#refs/tags/}" >> ${GITHUB_ENV}
+
+      - name: Package Source
+        run: |
+          mkdir -p build/source
+          ./packaging/source/buildpackage.sh "${GIT_TAG}" "${PWD}/build/source"
+
+      - name: Upload Packages
+        uses: svenstaro/upload-release-action@v2
+        with:
+          repo_token: ${{ secrets.GITHUB_TOKEN }}
+          tag: ${{ github.ref }}
+          overwrite: true
+          file_glob: true
+          file: build/source/*
+
+  linux:
+    name: Linux AppImages
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Clone Repository
+        uses: actions/checkout@v3
+
+      - name: Install .NET 6.0
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'

      - name: Prepare Environment
        run: echo "GIT_TAG=${GITHUB_REF#refs/tags/}" >> ${GITHUB_ENV}
@@ -21,6 +53,7 @@ jobs:
      - name: Package AppImages
        run: |
          mkdir -p build/linux
+          sudo apt install libfuse2
          ./packaging/linux/buildpackage.sh "${GIT_TAG}" "${PWD}/build/linux"

      - name: Upload Packages
@@ -33,16 +66,21 @@ jobs:
          file: build/linux/*

  macos:
-    name: macOS Disk Images
-    runs-on: macos-10.15
+    name: macOS Disk Image
+    runs-on: macos-11
    steps:
      - name: Clone Repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
+
+      - name: Install .NET 6.0
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'

      - name: Prepare Environment
        run: echo "GIT_TAG=${GITHUB_REF#refs/tags/}" >> ${GITHUB_ENV}

-      - name: Package Disk Images
+      - name: Package Disk Image
        env:
          MACOS_DEVELOPER_IDENTITY: ${{ secrets.MACOS_DEVELOPER_IDENTITY }}
          MACOS_DEVELOPER_CERTIFICATE_BASE64: ${{ secrets.MACOS_DEVELOPER_CERTIFICATE_BASE64 }}
@@ -53,7 +91,7 @@ jobs:
          mkdir -p build/macos
          ./packaging/macos/buildpackage.sh "${GIT_TAG}" "${PWD}/build/macos"

-      - name: Upload Packages
+      - name: Upload Package
        uses: svenstaro/upload-release-action@v2
        with:
          repo_token: ${{ secrets.GITHUB_TOKEN }}
@@ -64,15 +102,21 @@ jobs:

  windows:
    name: Windows Installers
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
    steps:
      - name: Clone Repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
+
+      - name: Install .NET 6.0
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '6.0.x'

      - name: Prepare Environment
        run: |
          echo "GIT_TAG=${GITHUB_REF#refs/tags/}" >> ${GITHUB_ENV}
-          sudo apt install nsis
+          sudo apt-get update
+          sudo apt-get install nsis wine64

      - name: Package Installers
        run: |
--- a/.gitignore
+++ b/.gitignore
@@ -13,19 +13,10 @@ obj
 _ReSharper.*/
 /.vs

+# Visual Studio Code
+/.vscode/settings.json
+
 # binaries
-mods/*/*.dll
-mods/*/*.mdb
-mods/*/*.pdb
-/*.dll
-/*.dll.config
-/*.so
-/*.dylib
-/*.pdb
-/*.mdb
-/*.exe
-/*.exe.config
-thirdparty/download/*
 IP2LOCATION-LITE-DB1.IPV6.BIN.ZIP

 # backup files by various editors
@@ -50,10 +41,6 @@ Settings.md
 openra.6
 update.log

-# StyleCop
-*.Cache
-StyleCopViolations.xml
-
 # SublimeText
 *.sublime-project
 *.sublime-workspace
--- a/.vscode/extensions.json
+++ b/.vscode/extensions.json
@@ -1,7 +1,9 @@
 {
 	"recommendations": [
 		"ms-dotnettools.csharp",
+		"openra.oraide-vscode",
+		"openra.vscode-openra-lua",
 		"EditorConfig.EditorConfig",
-		"ms-vscode.mono-debug"
+		"macabeus.vscode-fluent",
 	]
 }
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -3,62 +3,60 @@
 	"configurations": [
 		{
 			"name": "Launch (TD)",
-			"type": "clr",
-			"linux": {
-				"type": "mono"
-			},
-			"osx": {
-				"type": "mono"
-			},
+			"type": "coreclr",
 			"request": "launch",
-			"program": "${workspaceRoot}/OpenRA.Game.exe",
-			"cwd": "${workspaceRoot}",
-			"args": ["Game.Mod=cnc"],
+			"program": "${workspaceRoot}/bin/OpenRA.dll",
+			"windows": {
+				"program": "${workspaceRoot}/bin/OpenRA.exe",
+			},
+			"args": ["Game.Mod=cnc", "Engine.EngineDir=.."],
 			"preLaunchTask": "build",
 		},
 		{
 			"name": "Launch (RA)",
-			"type": "clr",
-			"linux": {
-				"type": "mono"
-			},
-			"osx": {
-				"type": "mono"
-			},
+			"type": "coreclr",
 			"request": "launch",
-			"program": "${workspaceRoot}/OpenRA.Game.exe",
-			"cwd": "${workspaceRoot}",
-			"args": ["Game.Mod=ra"],
+			"program": "${workspaceRoot}/bin/OpenRA.dll",
+			"windows": {
+				"program": "${workspaceRoot}/bin/OpenRA.exe",
+			},
+			"args": ["Game.Mod=ra", "Engine.EngineDir=.."],
 			"preLaunchTask": "build",
 		},
 		{
 			"name": "Launch (D2k)",
-			"type": "clr",
-			"linux": {
-				"type": "mono"
-			},
-			"osx": {
-				"type": "mono"
-			},
+			"type": "coreclr",
 			"request": "launch",
-			"program": "${workspaceRoot}/OpenRA.Game.exe",
-			"cwd": "${workspaceRoot}",
-			"args": ["Game.Mod=d2k"],
+			"program": "${workspaceRoot}/bin/OpenRA.dll",
+			"windows": {
+				"program": "${workspaceRoot}/bin/OpenRA.exe",
+			},
+			"args": ["Game.Mod=d2k", "Engine.EngineDir=.."],
 			"preLaunchTask": "build",
 		},
 		{
 			"name": "Launch (TS)",
-			"type": "clr",
-			"linux": {
-				"type": "mono"
-			},
-			"osx": {
-				"type": "mono"
-			},
+			"type": "coreclr",
 			"request": "launch",
-			"program": "${workspaceRoot}/OpenRA.Game.exe",
-			"cwd": "${workspaceRoot}",
-			"args": ["Game.Mod=ts"],
+			"program": "${workspaceRoot}/bin/OpenRA.dll",
+			"windows": {
+				"program": "${workspaceRoot}/bin/OpenRA.exe",
+			},
+			"args": ["Game.Mod=ts", "Engine.EngineDir=.."],
+			"preLaunchTask": "build",
+		},
+		{
+			"name": "Launch Utility",
+			"type": "coreclr",
+			"request": "launch",
+			"program": "${workspaceRoot}/bin/OpenRA.Utility.dll",
+			"windows": {
+				"program": "${workspaceRoot}/bin/OpenRA.Utility.exe",
+			},
+			"args": ["all", "--docs", "{DEV_VERSION}"],
+			"env": {
+				"ENGINE_DIR": ".."
+			},
 			"preLaunchTask": "build",
 		},
 	]
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,3 +0,0 @@
-{
-	"omnisharp.enableRoslynAnalyzers": true
-}
--- a/.vscode/tasks.json
+++ b/.vscode/tasks.json
@@ -1,13 +1,36 @@
 {
 	"version": "2.0.0",
+	"options": {
+		"env": {
+			"ENGINE_DIR": ".."
+		}
+	},
 	"tasks": [
 		{
 			"label": "build",
 			"command": "make",
-			"args": ["all"],
+			"args": ["all", "CONFIGURATION=Debug"],
 			"windows": {
 				"command": "make.cmd"
 			}
+		},
+		{
+			"label": "Run Utility",
+			"command": "dotnet ${workspaceRoot}/bin/OpenRA.Utility.dll ${input:modId} ${input:command}",
+			"type": "shell",
 		}
+	],
+	"inputs": [
+		{
+			"id": "modId",
+			"description": "ID of the mod to run",
+			"default": "all",
+			"type": "promptString"
+		}, {
+			"id": "command",
+			"description": "Name of the command + parameters",
+			"default": "",
+			"type": "promptString"
+		},
 	]
 }
--- a/38
+++ b/38
@@ -2,28 +2,30 @@ OpenRA wouldn't be where it is today without the
 hard work of many contributors.

 The OpenRA developers are:
-    * Chris Forbes (chrisf)
+    * Gustas Kažukauskas (PunkPun)
    * Lukas Franke (abcdefg30)
-    * Paul Chote (pchote)
-    * Reaperrr
+    * Matthias Mailänder (Mailaender)

 Previous developers included:
    * Alli Witheford (alzeih)
    * Caleb Anderson (RobotCaleb)
+    * Chris Forbes (chrisf)
    * Curtis Shmyr (hamb)
    * Daniel Hernandez (Mancano)
    * Igor Popov (ihptru)
-    * Matthias Mailänder (Mailaender)
    * Megan Bowra-Dean (beedee)
    * Mike Bundy (kehaar)
    * Oliver Brakmann (obrakmann)
+    * Paul Chote (pchote)
    * Pavel Penev (penev92)
+    * Reaperrr
    * Robert Pepperell (ytinasni)
    * ScottNZ
    * Tom Roostan (RoosterDragon)

 Also thanks to:
    * abmyii
+    * anvilvapre (anvilvapre)
    * Adam Valy (Tschokky)
    * Akseli Virtanen (RAGEQUIT)
    * Alexander Fast (mizipzor)
@@ -37,6 +39,7 @@ Also thanks to:
    * Arik Lirette (Angusm3)
    * Barnaby Smith (mvi)
    * Bellator
+    * Bernd Stellwag (burned42)
    * Biofreak
    * Braxton Williams (Buddytex)
    * Brendan Gluth (Mechanical_Man)
@@ -46,6 +49,7 @@ Also thanks to:
    * Chris Cameron (Vesuvian)
    * Chris Grant (Unit158)
    * Christer Ulfsparre (Holloweye)
+    * Christoph Lahner (chlah)
    * clem
    * Cody Brittain (Generalcamo)
    * Constantin Helmig (CH4Code)
@@ -58,6 +62,7 @@ Also thanks to:
    * DeadlySurprise
    * Dmitri Suvorov (suvjunmd)
    * dtluna
+    * Eduardo Cáceres (eduherminio)
    * Erasmus Schroder (rasco)
    * Eric Bajumpaa (SteelPhase)
    * Evgeniy Sergeev (evgeniysergeev)
@@ -69,12 +74,14 @@ Also thanks to:
    * Glenn Martin Jensen (Baxxster)
    * Gordon Martin (Happy0)
    * Guido Lipke (LipkeGu)
+    * Guillermo Cuenca (Wylli)
    * Hervé Matysiak (Herve-M)
    * Huw Pascoe
    * Ian T. Jacobsen (Smilex)
    * Imago
    * Iran
    * Ishan Bhargava (ishantheperson)
+    * Ivaylo Draganov (dragunoff)
    * Jacob Dufault (jacobdufault)
    * James Dunne (jsd)
    * James Gilbert (DSUK)
@@ -113,6 +120,7 @@ Also thanks to:
    * Mike Gagné (AngryBirdz)
    * Muh
    * Mustafa Alperen Seki (MustaphaTR)
+    * Nathan Nichols (cracksmoka420)
    * Neil Shivkar (havok13888)
    * Nikolay Fomin (netnazgul)
    * Nooze
@@ -135,12 +143,12 @@ Also thanks to:
    * Rikhardur Bjarni Einarsson (WolfGaming)
    * Sascha Biedermann (bidifx)
    * Sean Hunt (coppro)
-    * Sebastien Kerguen (xanax)
    * Shawn Collins (UberWaffe)
    * Simon Verbeke (Saticmotion)
    * Stuart McHattie (SDJMcHattie)
    * Taryn Hill (Phrohdoh)
    * Teemu Nieminen (Temeez)
+    * Thomas Christlieb (ThomasChr)
    * Tim Mylemans (gecko)
    * Tirili
    * Tomas Einarsson (Mesacer)
@@ -173,9 +181,17 @@ under the MIT license.
 Using FuzzyLogicLibrary (fuzzynet) by Dmitry
 Kaluzhny and released under the GNU GPL terms.

-Using Open.Nat by Lucas Ontivero, based on the work
-of Alan McGovern and Ben Motmans and distributed
-under the MIT license.
+Using Mono.Nat by Alan McGovern, Ben Motmans,
+Nicholas Terry distributed under the MIT license.
+
+Using MP3Sharp by Robert Bruke and Zane Wagner
+licensed under the GNU LGPL Version 3.
+
+Using TagLib# by Stephen Shaw licensed under the
+GNU LGPL Version 2.1.
+
+Using NVorbis by Andrew Ward distributed under
+the MIT license.

 Using ICSharpCode.SharpZipLib initially by Mike
 Krueger and distributed under the GNU GPL terms.
@@ -191,6 +207,12 @@ distributed under MIT License.

 Using ANGLE distributed under the BS3 3-Clause license.

+Using Pfim developed by Nick Babcock
+distributed under the MIT license.
+
+Using Linguini by the Space Station 14 team
+licensed under Apache and MIT terms.
+
 This site or product includes IP2Location LITE data
 available from http://www.ip2location.com.

--- a/CODE_OF_CONDUCT.md
+++ b/CODE_OF_CONDUCT.md
@@ -56,8 +56,8 @@ further defined and clarified by project maintainers.

 Instances of abusive, harassing, or otherwise unacceptable behavior may be
 reported by private-messaging a project team member (users with a + in front
-of their name) via our IRC channel (#openra on freenode –
-[webchat](http://webchat.freenode.net/?channels=openra)). All
+of their name) via our IRC channel (#openra on Libera –
+[webchat](https://web.libera.chat/#openra)). All
 complaints will be reviewed and investigated and will result in a response that
 is deemed necessary and appropriate to the circumstances. The project team is
 obligated to maintain confidentiality with regard to the reporter of an incident.
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -0,0 +1,58 @@
+<Project>
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Optimize>true</Optimize>
+    <LangVersion>9</LangVersion>
+    <DebugSymbols>true</DebugSymbols>
+    <EngineRootPath Condition="'$(EngineRootPath)' == ''">..</EngineRootPath>
+    <OutputPath>$(EngineRootPath)/bin</OutputPath>
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <ExternalConsole>false</ExternalConsole>
+    <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    <Nullable>disable</Nullable>
+    <Product>OpenRA</Product>
+    <Copyright>Copyright (c) The OpenRA Developers and Contributors</Copyright>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <TargetFramework Condition="'$(MSBuildRuntimeType)'!='Mono'">net6.0</TargetFramework>
+    <TargetFramework Condition="'$(MSBuildRuntimeType)'=='Mono'">netstandard2.1</TargetFramework>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <TargetPlatform Condition="$([MSBuild]::IsOsPlatform('Windows'))">win-x64</TargetPlatform>
+    <TargetPlatform Condition="$([MSBuild]::IsOsPlatform('Linux'))">linux-x64</TargetPlatform>
+    <TargetPlatform Condition="$([MSBuild]::IsOsPlatform('OSX'))">osx-x64</TargetPlatform>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)' == 'Debug'">
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <Optimize>false</Optimize>
+    <!-- Enable only for Debug builds to improve compile-time performance for Release builds -->
+    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+    <!-- Enabling GenerateDocumentationFile is required for IDE0005 (Remove unnecessary import) 
+      rule to run in command line builds. https://github.com/dotnet/roslyn/issues/41640
+      Enable only for Debug builds to improve compile-time performance for Release builds -->
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Work around an issue where Rider does not detect files in the project root using the default glob -->
+    <Compile Include="**/*.cs" Exclude="$(DefaultItemExcludes)" />
+  </ItemGroup>
+
+  <Target Name="DisableAnalyzers" BeforeTargets="CoreCompile" Condition="'$(Configuration)'=='Release'">
+    <!-- Disable code style analysis on Release builds to improve compile-time performance -->
+    <ItemGroup Condition="'$(Configuration)'=='Release'">
+      <Analyzer Remove="@(Analyzer)" />
+    </ItemGroup>
+  </Target>
+
+  <!-- StyleCop -->
+  <ItemGroup>
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.435" PrivateAssets="All" />
+  </ItemGroup>
+</Project>
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -8,104 +8,76 @@ Windows

 Compiling OpenRA requires the following dependencies:
 * [Windows PowerShell >= 4.0](http://microsoft.com/powershell) (included by default in recent Windows 10 versions)
-* [.NET Framework 4.7.2 (Developer Pack)](https://dotnet.microsoft.com/download/dotnet-framework/net472) (or via Visual Studio 2017)
-* [.NET Core 2.2 SDK](https://dotnet.microsoft.com/download/dotnet-core/2.2) (or via Visual Studio 2017)
+* [.NET 6 SDK](https://dotnet.microsoft.com/download/dotnet/6.0) (or via Visual Studio)

-
-To compile OpenRA, open the `OpenRA.sln` solution in the main folder, build it from the command-line with MSBuild or use the Makefile analogue command `make all` scripted in PowerShell syntax.
+To compile OpenRA, open the `OpenRA.sln` solution in the main folder, build it from the command-line with `dotnet` or use the Makefile analogue command `make all` scripted in PowerShell syntax.

 Run the game with `launch-game.cmd`. It can be handed arguments that specify the exact mod one wishes to run, for example, run `launch-game.cmd Game.Mod=ra` to launch Red Alert, `launch-game.cmd Game.Mod=cnc` to start Tiberian dawn or `launch-game.cmd Game.Mod=d2k` to launch Dune 2000.

 Linux
 =====

-Mono, version 5.18 or later, is required to compile OpenRA. You can add the [upstream mono repository](https://www.mono-project.com/download/stable/#download-lin) for your distro to obtain the latest version if your system packages are not sufficient.
+.NET 6 or Mono (version 6.12 or later) is required to compile OpenRA. We recommend using .NET 6 when possible, as Mono is poorly packaged by most Linux distributions (e.g. missing the required `msbuild` toolchain), and has been deprecated as a standalone project.

-To compile OpenRA, run `make` from the command line. After this one can run the game with `./launch-game.sh`. It is also possible to specify the mod you wish to run from the command line, e.g. with `./launch-game.sh Game.Mod=ts` if you wish to try the experimental Tiberian Sun mod.
+The [.NET 6 download page](https://dotnet.microsoft.com/download/dotnet/6.0) provides repositories for various package managers and binary releases for several architectures. If you prefer to use Mono, we suggest adding the [upstream repository](https://www.mono-project.com/download/stable/#download-lin) for your distro to obtain the latest version and the `msbuild` toolchain.
+
+To compile OpenRA, run `make` from the command line (or `make RUNTIME=mono` if using Mono). After this one can run the game with `./launch-game.sh`. It is also possible to specify the mod you wish to run from the command line, e.g. with `./launch-game.sh Game.Mod=ts` if you wish to try the experimental Tiberian Sun mod.

 The default behaviour on the x86_64 architecture is to download several pre-compiled native libraries using the Nuget packaging manager. If you prefer to use system libraries, compile instead using `make TARGETPLATFORM=unix-generic`.

-If you choose to use system libraries, or your system is not x86_64, you will need to install the following using your system package manager:
-* [SDL 2](http://www.libsdl.org/download-2.0.php)
-* [FreeType](http://gnuwin32.sourceforge.net/packages/freetype.htm)
-* [OpenAL](http://kcat.strangesoft.net/openal.html)
-* [liblua 5.1](http://luabinaries.sourceforge.net/download.html)
+If you choose to use system libraries, or your system is not x86_64, you will need to install [SDL 2](https://www.libsdl.org/download-2.0.php), [FreeType](http://gnuwin32.sourceforge.net/packages/freetype.htm), [OpenAL](https://openal-soft.org/), and [liblua 5.1](http://luabinaries.sourceforge.net/download.html) before compiling OpenRA.

-Type `sudo make install` for system-wide installation. Run `sudo make install-linux-shortcuts` to get startup scripts, icons and desktop files. You can then run the Red Alert by executing the `openra-ra` command, the Dune 2000 mod by running the `openra-d2k` command and Tiberian Dawn by the `openra-cnc` command. Alternatively, you can also run these mods by clicking on their desktop shortcuts if you ran `sudo make install-linux-shortcuts`.
+These can be installed using your package manager on various distros:

-Arch Linux
----------
-
-It is important to note there is an unofficial [`openra-git`](https://aur.archlinux.org/packages/openra-git) package in the Arch User Repository (AUR) of Arch Linux. If manually compiling is the way you wish to go the build and runtime dependencies can be installed with:
+<details><summary>Arch Linux</summary>

 ```
-sudo pacman -S mono openal libgl freetype2 sdl2 lua51 xdg-utils zenity
+sudo pacman -S openal libgl freetype2 sdl2 lua51
 ```
-
-Debian/Ubuntu
-------------
-
-:warning: The `mono` packages in the Ubuntu < 19.04 and Debian < 10 repositories are too old to support OpenRA. :warning:
-
-See the instructions under the *Linux* section above to upgrade `mono` using the upstream releases if needed.
+</details>
+<details><summary>Debian/Ubuntu</summary>

 ```
-sudo apt install mono-devel libfreetype6 libopenal1 liblua5.1-0 libsdl2-2.0-0 xdg-utils zenity wget
+sudo apt install libfreetype6 libopenal1 liblua5.1-0 libsdl2-2.0-0
 ```
-
-Fedora
------
-
-:warning: The `mono` packages in the Fedora repositories are too old to support OpenRA. :warning:
-
-See the instructions under the *Linux* section above to upgrade `mono` using the upstream releases.
-
+</details>
+<details><summary>Fedora</summary>

 ```
-sudo dnf install "pkgconfig(mono)" SDL2 freetype "lua = 5.1" openal-soft xdg-utils zenity
+sudo dnf install SDL2 freetype "lua = 5.1" openal-soft
 ```
-
-Gentoo
------
+</details>
+<details><summary>Gentoo</summary>

 ```
-sudo emerge -av dev-lang/mono dev-dotnet/libgdiplus media-libs/freetype:2 media-libs/libsdl2 media-libs/openal virtual/jpeg virtual/opengl '=dev-lang/lua-5.1.5*' x11-misc/xdg-utils gnome-extra/zenity
+sudo emerge -av media-libs/freetype:2 media-libs/libsdl2 media-libs/openal virtual/opengl '=dev-lang/lua-5.1.5*'
 ```
-
-Mageia
------
+</details>
+<details><summary>Mageia</summary>

 ```
-sudo dnf install "pkgconfig(mono)" SDL2 freetype "lib*lua5.1" "lib*freetype2" "lib*sdl2.0_0" openal-soft xdg-utils zenity
+sudo dnf install SDL2 freetype "lib*lua5.1" "lib*freetype2" "lib*sdl2.0_0" openal-soft
 ```
-
-openSUSE
--------
+</details>
+<details><summary>openSUSE</summary>

 ```
-sudo zypper in mono-devel openal-soft freetype2 SDL2 lua51 xdg-utils zenity
+sudo zypper in openal-soft freetype2 SDL2 lua51
 ```
-
-Red Hat Enterprise Linux (and rebuilds, e.g. CentOS)
----------------------------------------------------
-
+</details>
+<details><summary>Red Hat Enterprise Linux (and rebuilds, e.g. CentOS)</summary>
 The EPEL repository is required in order for the following command to run properly.

 ```
-sudo yum install "pkgconfig(mono)" SDL2 freetype "lua = 5.1" openal-soft xdg-utils zenity
+sudo yum install SDL2 freetype "lua = 5.1" openal-soft
 ```
+</details>
+
+Type `sudo make install` for system-wide installation. Run `sudo make install-linux-shortcuts` to get startup scripts, icons and desktop files. You can then run the Red Alert by executing the `openra-ra` command, the Dune 2000 mod by running the `openra-d2k` command and Tiberian Dawn by the `openra-cnc` command. Alternatively, you can also run these mods by clicking on their desktop shortcuts if you ran `sudo make install-linux-shortcuts`.

 macOS
 =====

-Before compiling OpenRA you must install the following dependencies:
-* [Mono >= 5.18](https://www.mono-project.com/download/stable/#download-mac)
-
-To compile OpenRA, run `make` from the command line. Run with `./launch-game.sh`.
-
-The default behaviour is to download several pre-compiled native libraries using the Nuget packaging manager. If you prefer to use system libraries, compile instead using `make TARGETPLATFORM=unix-generic`. If you choose to use system libraries you will need to install:
-* [SDL 2](http://www.libsdl.org/download-2.0.php) (`brew install sdl2`)
-* [FreeType](http://gnuwin32.sourceforge.net/packages/freetype.htm) (`brew install freetype`)
-* [OpenAL](http://kcat.strangesoft.net/openal.html) (`brew install openal-soft`)
-* [liblua 5.1](http://luabinaries.sourceforge.net/download.html) (`brew install lua@5.1`)
+[.NET 6](https://dotnet.microsoft.com/download/dotnet/6.0) or [Mono](https://www.mono-project.com/download/stable/#download-mac) (version 6.12 or later) is required to compile OpenRA. We recommend using .NET 6 unless you are running a very old version of macOS (10.9 through 10.14).

+To compile OpenRA, run `make` from the command line (or `make RUNTIME=mono` if using Mono). Run with `./launch-game.sh`.
--- a/154
+++ b/154
@@ -1,42 +1,40 @@
 ############################# INSTRUCTIONS #############################
 #
 # to compile, run:
-#   make [DEBUG=true]
+#   make
+#
+# to compile using Mono (version 6.12 or greater) instead of .NET 6, run:
+#   make RUNTIME=mono
 #
 # to compile using system libraries for native dependencies, run:
-#   make [DEBUG=true] TARGETPLATFORM=unix-generic
+#   make [RUNTIME=net6] TARGETPLATFORM=unix-generic
 #
 # to check the official mods for erroneous yaml files, run:
-#   make test
+#   make [RUNTIME=net6] test
 #
 # to check the engine and official mod dlls for code style violations, run:
-#   make check
+#   make [RUNTIME=net6] check
 #
 # to compile and install Red Alert, Tiberian Dawn, and Dune 2000, run:
-#   make [prefix=/foo] [bindir=/bar/bin] install
+#   make [RUNTIME=net6] [prefix=/foo] [bindir=/bar/bin] install
 #
-# to install Linux startup scripts, desktop files, icons, and MIME metadata
+# to compile and install Red Alert, Tiberian Dawn, and Dune 2000
+# using system libraries for native dependencies, run:
+#   make [prefix=/foo] [bindir=/bar/bin] TARGETPLATFORM=unix-generic install
+#
+# to install FreeDesktop startup scripts, desktop files, icons, and MIME metadata
 #   make install-linux-shortcuts
 #
-# to install Linux AppStream metadata
+# to install FreeDesktop AppStream metadata
 #   make install-linux-appdata
 #
+# to install the Unix man page
+#   make install-man
+#
 # for help, run:
 #   make help
 #

-############################## TOOLCHAIN ###############################
-#
-# List of .NET assemblies that we can guarantee exist
-WHITELISTED_OPENRA_ASSEMBLIES = OpenRA.exe OpenRA.Utility.exe OpenRA.Server.exe OpenRA.Platforms.Default.dll OpenRA.Game.dll OpenRA.Mods.Common.dll OpenRA.Mods.Cnc.dll OpenRA.Mods.D2k.dll
-
-# These are explicitly shipped alongside our core files by the packaging script
-WHITELISTED_THIRDPARTY_ASSEMBLIES = ICSharpCode.SharpZipLib.dll FuzzyLogicLibrary.dll Eluant.dll BeaconLib.dll Open.Nat.dll SDL2-CS.dll OpenAL-CS.Core.dll DiscordRPC.dll Newtonsoft.Json.dll
-
-# These are shipped in our custom minimal mono runtime and also available in the full system-installed .NET/mono stack
-# This list *must* be kept in sync with the files packaged by the AppImageSupport and OpenRALauncherOSX repositories
-WHITELISTED_CORE_ASSEMBLIES = mscorlib.dll System.dll System.Configuration.dll System.Core.dll System.Numerics.dll System.Security.dll System.Xml.dll Mono.Security.dll netstandard.dll
-
 ######################### UTILITIES/SETTINGS ###########################
 #
 # Install locations for local installs and downstream packaging
@@ -48,125 +46,165 @@ bindir ?= $(prefix)/bin
 libdir ?= $(prefix)/lib
 gameinstalldir ?= $(libdir)/openra

-BIN_INSTALL_DIR = $(DESTDIR)$(bindir)
-DATA_INSTALL_DIR = $(DESTDIR)$(datadir)
-OPENRA_INSTALL_DIR = $(DESTDIR)$(gameinstalldir)
-
 # Toolchain
 CWD = $(shell pwd)
 MSBUILD = msbuild -verbosity:m -nologo
+DOTNET = dotnet
 MONO = mono
 RM = rm
 RM_R = $(RM) -r
 RM_F = $(RM) -f
 RM_RF = $(RM) -rf

-VERSION = $(shell git name-rev --name-only --tags --no-undefined HEAD 2>/dev/null || echo git-`git rev-parse --short HEAD`)
+RUNTIME ?= net6
+CONFIGURATION ?= Release
+DOTNET_RID = $(shell ${DOTNET} --info | grep RID: | cut -w -f3)
+ARCH_X64 = $(shell echo ${DOTNET_RID} | grep x64)
+
+# Only for use in target version:
+VERSION := $(shell git name-rev --name-only --tags --no-undefined HEAD 2>/dev/null || (c=$$(git rev-parse --short HEAD 2>/dev/null) && echo git-$$c))

 # Detect target platform for dependencies if not given by the user
 ifndef TARGETPLATFORM
 UNAME_S := $(shell uname -s)
 UNAME_M := $(shell uname -m)
 ifeq ($(UNAME_S),Darwin)
+ifeq ($(ARCH_X64),)
+TARGETPLATFORM = osx-arm64
+else
 TARGETPLATFORM = osx-x64
+endif
 else
 ifeq ($(UNAME_M),x86_64)
 TARGETPLATFORM = linux-x64
 else
+ifeq ($(UNAME_M),aarch64)
+TARGETPLATFORM = linux-arm64
+else
 TARGETPLATFORM = unix-generic
 endif
 endif
 endif
-
-OPENRA_UTILITY = ENGINE_DIR=".." $(MONO) --debug bin/OpenRA.Utility.exe
+endif

 ##################### DEVELOPMENT BUILDS AND TESTS #####################
 #
 all:
-	@command -v $(firstword $(MSBUILD)) >/dev/null || (echo "OpenRA requires the '$(MSBUILD)' tool provided by Mono >= 5.18."; exit 1)
-	@$(MSBUILD) -t:Build -restore -p:Configuration=Release -p:TargetPlatform=$(TARGETPLATFORM)
+	@echo "Compiling in ${CONFIGURATION} mode..."
+ifeq ($(RUNTIME), mono)
+	@command -v $(firstword $(MSBUILD)) >/dev/null || (echo "OpenRA requires the '$(MSBUILD)' tool provided by Mono >= 6.12."; exit 1)
+	@$(MSBUILD) -t:Build -restore -p:Configuration=${CONFIGURATION} -p:TargetPlatform=$(TARGETPLATFORM)
+else
+	@$(DOTNET) build -c ${CONFIGURATION} -nologo -p:TargetPlatform=$(TARGETPLATFORM)
+endif
 ifeq ($(TARGETPLATFORM), unix-generic)
 	@./configure-system-libraries.sh
 endif
 	@./fetch-geoip.sh

+# dotnet clean and msbuild -t:Clean leave files that cause problems when switching between mono/dotnet
+# Deleting the intermediate / output directories ensures the build directory is actually clean
 clean:
-	@-$(RM_RF) ./bin ./*/bin ./*/obj
-	@$(MSBUILD) -t:Clean
+	@-$(RM_RF) ./bin ./*/obj
 	@-$(RM_F) IP2LOCATION-LITE-DB1.IPV6.BIN.ZIP

 check:
 	@echo
-	@echo "Compiling in debug mode..."
-	@$(MSBUILD) -t:build -restore -p:Configuration=Debug
-	@echo
-	@echo "Checking runtime assemblies..."
-	@$(OPENRA_UTILITY) all --check-runtime-assemblies $(WHITELISTED_OPENRA_ASSEMBLIES) $(WHITELISTED_THIRDPARTY_ASSEMBLIES) $(WHITELISTED_CORE_ASSEMBLIES)
+	@echo "Compiling in Debug mode..."
+ifeq ($(RUNTIME), mono)
+	@$(MSBUILD) -t:clean\;build -restore -p:Configuration=Debug -warnaserror -p:TargetPlatform=$(TARGETPLATFORM)
+else
+	@$(DOTNET) clean -c Debug --nologo --verbosity minimal
+	@$(DOTNET) build -c Debug -nologo -warnaserror -p:TargetPlatform=$(TARGETPLATFORM)
+endif
+ifeq ($(TARGETPLATFORM), unix-generic)
+	@./configure-system-libraries.sh
+endif
 	@echo
 	@echo "Checking for explicit interface violations..."
-	@$(OPENRA_UTILITY) all --check-explicit-interfaces
+	@./utility.sh all --check-explicit-interfaces
 	@echo
 	@echo "Checking for incorrect conditional trait interface overrides..."
-	@$(OPENRA_UTILITY) all --check-conditional-trait-interface-overrides
+	@./utility.sh all --check-conditional-trait-interface-overrides

 check-scripts:
 	@echo
 	@echo "Checking for Lua syntax errors..."
-	@luac -p $(shell find mods/*/maps/* -iname '*.lua')
-	@luac -p $(shell find lua/* -iname '*.lua')
-	@luac -p $(shell find mods/*/bits/scripts/* -iname '*.lua')
+	@find mods/*/maps/ mods/*/scripts/ -iname "*.lua" -print0 | xargs -0n1 luac -p

 test: all
 	@echo
 	@echo "Testing Tiberian Sun mod MiniYAML..."
-	@$(OPENRA_UTILITY) ts --check-yaml
+	@./utility.sh ts --check-yaml
 	@echo
 	@echo "Testing Dune 2000 mod MiniYAML..."
-	@$(OPENRA_UTILITY) d2k --check-yaml
+	@./utility.sh d2k --check-yaml
 	@echo
 	@echo "Testing Tiberian Dawn mod MiniYAML..."
-	@$(OPENRA_UTILITY) cnc --check-yaml
+	@./utility.sh cnc --check-yaml
 	@echo
 	@echo "Testing Red Alert mod MiniYAML..."
-	@$(OPENRA_UTILITY) ra --check-yaml
+	@./utility.sh ra --check-yaml
+
+tests:
+	@dotnet build OpenRA.Test/OpenRA.Test.csproj -c Debug --nologo -p:TargetPlatform=$(TARGETPLATFORM)
+	@echo
+	@dotnet test bin/OpenRA.Test.dll --test-adapter-path:.

 ############# LOCAL INSTALLATION AND DOWNSTREAM PACKAGING ##############
 #
 version: VERSION mods/ra/mod.yaml mods/cnc/mod.yaml mods/d2k/mod.yaml mods/ts/mod.yaml mods/modcontent/mod.yaml mods/all/mod.yaml
-	@sh -c '. ./packaging/functions.sh; set_engine_version $(VERSION) .'
-	@sh -c '. ./packaging/functions.sh; set_mod_version $(VERSION) mods/ra/mod.yaml mods/cnc/mod.yaml mods/d2k/mod.yaml mods/ts/mod.yaml mods/modcontent/mod.yaml mods/all/mod.yaml'
+ifeq ($(VERSION),)
+	$(error Unable to determine new version (requires git or override of variable VERSION))
+endif
+	@sh -c '. ./packaging/functions.sh; set_engine_version "$(VERSION)" .'
+	@sh -c '. ./packaging/functions.sh; set_mod_version "$(VERSION)" mods/ra/mod.yaml mods/cnc/mod.yaml mods/d2k/mod.yaml mods/ts/mod.yaml mods/modcontent/mod.yaml mods/all/mod.yaml'

 install:
-	@sh -c '. ./packaging/functions.sh; install_assemblies_mono $(CWD) $(OPENRA_INSTALL_DIR) $(TARGETPLATFORM) True True True'
-	@sh -c '. ./packaging/functions.sh; install_data $(CWD) $(OPENRA_INSTALL_DIR) cnc d2k ra'
+	@sh -c '. ./packaging/functions.sh; install_assemblies $(CWD) $(DESTDIR)$(gameinstalldir) $(TARGETPLATFORM) $(RUNTIME) True True True'
+	@sh -c '. ./packaging/functions.sh; install_data $(CWD) $(DESTDIR)$(gameinstalldir) cnc d2k ra'

 install-linux-shortcuts:
-	@sh -c '. ./packaging/functions.sh; install_linux_shortcuts $(CWD) $(OPENRA_INSTALL_DIR) $(BIN_INSTALL_DIR) $(DATA_INSTALL_DIR) $(VERSION) cnc d2k ra'
+	@sh -c '. ./packaging/functions.sh; install_linux_shortcuts $(CWD) "$(DESTDIR)" "$(gameinstalldir)" "$(bindir)" "$(datadir)" "$(shell head -n1 VERSION)" cnc d2k ra'

 install-linux-appdata:
-	@sh -c '. ./packaging/functions.sh; install_linux_appdata $(CWD) $(DATA_INSTALL_DIR) cnc d2k ra'
+	@sh -c '. ./packaging/functions.sh; install_linux_appdata $(CWD) "$(DESTDIR)" "$(datadir)" cnc d2k ra'
+
+install-man: all
+	@mkdir -p $(DESTDIR)$(mandir)/man6/
+	@./utility.sh all --man-page > $(DESTDIR)$(mandir)/man6/openra.6

 help:
 	@echo 'to compile, run:'
-	@echo '  make [DEBUG=true]'
+	@echo '  make'
+	@echo
+	@echo 'to compile using Mono (version 6.12 or greater) instead of .NET 6, run:'
+	@echo '  make RUNTIME=mono'
 	@echo
 	@echo 'to compile using system libraries for native dependencies, run:'
-	@echo '  make [DEBUG=true] TARGETPLATFORM=unix-generic'
+	@echo '  make [RUNTIME=net6] TARGETPLATFORM=unix-generic'
 	@echo
 	@echo 'to check the official mods for erroneous yaml files, run:'
-	@echo '  make test'
+	@echo '  make [RUNTIME=net6] [TREAT_WARNINGS_AS_ERRORS=false] test'
 	@echo
 	@echo 'to check the engine and official mod dlls for code style violations, run:'
-	@echo '  make test'
+	@echo '  make [RUNTIME=net6] check'
 	@echo
 	@echo 'to compile and install Red Alert, Tiberian Dawn, and Dune 2000 run:'
-	@echo '  make [prefix=/foo] install'
+	@echo '  make [RUNTIME=net6] [prefix=/foo] [TARGETPLATFORM=unix-generic] install'
 	@echo
-	@echo 'to install Linux startup scripts, desktop files, icons, and MIME metadata'
+	@echo 'to compile and install Red Alert, Tiberian Dawn, and Dune 2000'
+	@echo 'using system libraries for native dependencies, run:'
+	@echo '   make [RUNTIME=net6] [prefix=/foo] [bindir=/bar/bin] TARGETPLATFORM=unix-generic install'
+	@echo
+	@echo 'to install FreeDesktop startup scripts, desktop files, icons, and MIME metadata'
 	@echo '  make install-linux-shortcuts'
 	@echo
-	@echo 'to install Linux AppStream metadata'
+	@echo 'to install FreeDesktop AppStream metadata'
 	@echo '  make install-linux-appdata'
+	@echo
+	@echo 'to install a Unix man page'
+	@echo '  make install-man'

 ########################### MAKEFILE SETTINGS ##########################
 #
@@ -174,4 +212,4 @@ help:

 .SUFFIXES:

-.PHONY: all clean check check-scripts test version install install-linux-shortcuts install-linux-appdata help
+.PHONY: all clean check check-scripts test version install install-linux-shortcuts install-linux-appdata install-man help
--- a/OpenRA.Game/Activities/Activity.cs
+++ b/OpenRA.Game/Activities/Activity.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -53,15 +53,15 @@ namespace OpenRA.Activities
 		Activity childActivity;
 		protected Activity ChildActivity
 		{
-			get { return SkipDoneActivities(childActivity); }
-			private set { childActivity = value; }
+			get => SkipDoneActivities(childActivity);
+			private set => childActivity = value;
 		}

 		Activity nextActivity;
 		public Activity NextActivity
 		{
-			get { return SkipDoneActivities(nextActivity); }
-			private set { nextActivity = value; }
+			get => SkipDoneActivities(nextActivity);
+			private set => nextActivity = value;
 		}

 		internal static Activity SkipDoneActivities(Activity first)
@@ -74,19 +74,19 @@ namespace OpenRA.Activities
 			// drop valid activities queued after it. Walk the queue until we find a valid activity or
 			// (more likely) run out of activities.
 			while (first != null && first.State == ActivityState.Done)
-				first = first.NextActivity;
+				first = first.nextActivity;

 			return first;
 		}

 		public bool IsInterruptible { get; protected set; }
 		public bool ChildHasPriority { get; protected set; }
-		public bool IsCanceling { get { return State == ActivityState.Canceling; } }
+		public bool IsCanceling => State == ActivityState.Canceling;
 		bool finishing;
 		bool firstRunCompleted;
 		bool lastRun;

-		public Activity()
+		protected Activity()
 		{
 			IsInterruptible = true;
 			ChildHasPriority = true;
@@ -95,7 +95,7 @@ namespace OpenRA.Activities
 		public Activity TickOuter(Actor self)
 		{
 			if (State == ActivityState.Done)
-				throw new InvalidOperationException("Actor {0} attempted to tick activity {1} after it had already completed.".F(self, GetType()));
+				throw new InvalidOperationException($"Actor {self} attempted to tick activity {GetType()} after it had already completed.");

 			if (State == ActivityState.Queued)
 			{
@@ -105,7 +105,7 @@ namespace OpenRA.Activities
 			}

 			if (!firstRunCompleted)
-				throw new InvalidOperationException("Actor {0} attempted to tick activity {1} before running its OnFirstRun method.".F(self, GetType()));
+				throw new InvalidOperationException($"Actor {self} attempted to tick activity {GetType()} before running its OnFirstRun method.");

 			// Only run the parent tick when the child is done.
 			// We must always let the child finish on its own before continuing.
@@ -120,7 +120,8 @@ namespace OpenRA.Activities
 				lastRun = Tick(self);

 			// Avoid a single tick delay if the childactivity was just queued.
-			if (ChildActivity != null && ChildActivity.State == ActivityState.Queued)
+			var ca = ChildActivity;
+			if (ca != null && ca.State == ActivityState.Queued)
 			{
 				if (ChildHasPriority)
 					lastRun = TickChild(self) && finishing;
@@ -206,18 +207,18 @@ namespace OpenRA.Activities

 		public void Queue(Activity activity)
 		{
-			if (NextActivity != null)
-				NextActivity.Queue(activity);
-			else
-				NextActivity = activity;
+			var it = this;
+			while (it.nextActivity != null)
+				it = it.nextActivity;
+			it.nextActivity = activity;
 		}

 		public void QueueChild(Activity activity)
 		{
-			if (ChildActivity != null)
-				ChildActivity.Queue(activity);
+			if (childActivity != null)
+				childActivity.Queue(activity);
 			else
-				ChildActivity = activity;
+				childActivity = activity;
 		}

 		/// <summary>
@@ -269,15 +270,21 @@ namespace OpenRA.Activities

 		public IEnumerable<T> ActivitiesImplementing<T>(bool includeChildren = true) where T : IActivityInterface
 		{
-			if (includeChildren && ChildActivity != null)
-				foreach (var a in ChildActivity.ActivitiesImplementing<T>())
-					yield return a;
+			// Skips Done child and next activities
+			if (includeChildren)
+			{
+				var ca = ChildActivity;
+				if (ca != null)
+					foreach (var a in ca.ActivitiesImplementing<T>())
+						yield return a;
+			}

 			if (this is T)
 				yield return (T)(object)this;

-			if (NextActivity != null)
-				foreach (var a in NextActivity.ActivitiesImplementing<T>())
+			var na = NextActivity;
+			if (na != null)
+				foreach (var a in na.ActivitiesImplementing<T>())
 					yield return a;
 		}
 	}
--- a/OpenRA.Game/Activities/CallFunc.cs
+++ b/OpenRA.Game/Activities/CallFunc.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -22,11 +22,11 @@ namespace OpenRA.Activities
 			IsInterruptible = interruptible;
 		}

-		Action a;
+		readonly Action a;

 		public override bool Tick(Actor self)
 		{
-			a?.Invoke();
+			a.Invoke();
 			return true;
 		}
 	}
--- a/OpenRA.Game/Actor.cs
+++ b/OpenRA.Game/Actor.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -11,6 +11,7 @@

 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
 using Eluant;
@@ -23,9 +24,21 @@ using OpenRA.Traits;

 namespace OpenRA
 {
+	[Flags]
+	public enum SystemActors
+	{
+		Player = 0,
+		EditorPlayer = 1,
+		World = 2,
+		EditorWorld = 4
+	}
+
 	public sealed class Actor : IScriptBindable, IScriptNotifyBind, ILuaTableBinding, ILuaEqualityBinding, ILuaToStringBinding, IEquatable<Actor>, IDisposable
 	{
-		internal struct SyncHash
+		/// <summary>Value used to represent an invalid token.</summary>
+		public const int InvalidConditionToken = -1;
+
+		internal readonly struct SyncHash
 		{
 			public readonly ISync Trait;
 			readonly Func<object, int> hashFunction;
@@ -48,57 +61,49 @@ namespace OpenRA
 		Activity currentActivity;
 		public Activity CurrentActivity
 		{
-			get { return Activity.SkipDoneActivities(currentActivity); }
-			private set { currentActivity = value; }
+			get => Activity.SkipDoneActivities(currentActivity);
+			private set => currentActivity = value;
 		}

 		public int Generation;
 		public Actor ReplacedByActor;

-		public IEffectiveOwner EffectiveOwner { get; private set; }
-		public IOccupySpace OccupiesSpace { get; private set; }
-		public ITargetable[] Targetables { get; private set; }
+		public IEffectiveOwner EffectiveOwner { get; }
+		public IOccupySpace OccupiesSpace { get; }
+		public ITargetable[] Targetables { get; }
+		public IEnumerable<ITargetablePositions> EnabledTargetablePositions { get; private set; }

-		public bool IsIdle { get { return CurrentActivity == null; } }
-		public bool IsDead { get { return Disposed || (health != null && health.IsDead); } }
+		public bool IsIdle => CurrentActivity == null;
+		public bool IsDead => Disposed || (health != null && health.IsDead);

-		public CPos Location { get { return OccupiesSpace.TopLeft; } }
-		public WPos CenterPosition { get { return OccupiesSpace.CenterPosition; } }
+		public CPos Location => OccupiesSpace.TopLeft;
+		public WPos CenterPosition => OccupiesSpace.CenterPosition;

-		public WRot Orientation
-		{
-			get
-			{
-				return facing != null ? facing.Orientation : WRot.None;
-			}
-		}
+		public WRot Orientation => facing?.Orientation ?? WRot.None;

-		/// <summary>Value used to represent an invalid token.</summary>
-		public static readonly int InvalidConditionToken = -1;
-
-		class ConditionState
+		sealed class ConditionState
 		{
 			/// <summary>Delegates that have registered to be notified when this condition changes.</summary>
-			public readonly List<VariableObserverNotifier> Notifiers = new List<VariableObserverNotifier>();
+			public readonly List<VariableObserverNotifier> Notifiers = new();

 			/// <summary>Unique integers identifying granted instances of the condition.</summary>
-			public readonly HashSet<int> Tokens = new HashSet<int>();
+			public readonly HashSet<int> Tokens = new();
 		}

-		readonly Dictionary<string, ConditionState> conditionStates = new Dictionary<string, ConditionState>();
+		readonly Dictionary<string, ConditionState> conditionStates = new();

 		/// <summary>Each granted condition receives a unique token that is used when revoking.</summary>
-		readonly Dictionary<int, string> conditionTokens = new Dictionary<int, string>();
+		readonly Dictionary<int, string> conditionTokens = new();

 		int nextConditionToken = 1;

 		/// <summary>Cache of condition -> enabled state for quick evaluation of token counter conditions.</summary>
-		readonly Dictionary<string, int> conditionCache = new Dictionary<string, int>();
+		readonly Dictionary<string, int> conditionCache = new();

 		/// <summary>Read-only version of conditionCache that is passed to IConditionConsumers.</summary>
 		readonly IReadOnlyDictionary<string, int> readOnlyConditionCache;

-		internal SyncHash[] SyncHashes { get; private set; }
+		internal SyncHash[] SyncHashes { get; }

 		readonly IFacing facing;
 		readonly IHealth health;
@@ -110,10 +115,8 @@ namespace OpenRA
 		readonly IDefaultVisibility defaultVisibility;
 		readonly INotifyBecomingIdle[] becomingIdles;
 		readonly INotifyIdle[] tickIdles;
-		readonly IEnumerable<ITargetablePositions> enabledTargetablePositions;
-		WPos[] staticTargetablePositions;
+		readonly IEnumerable<WPos> enabledTargetableWorldPositions;
 		bool created;
-		bool setStaticTargetablePositions;

 		internal Actor(World world, string name, TypeDictionary initDict)
 		{
@@ -121,7 +124,7 @@ namespace OpenRA
 				.FirstOrDefault(i => i.Count() > 1);

 			if (duplicateInit != null)
-				throw new InvalidDataException("Duplicate initializer '{0}'".F(duplicateInit.Key.Name));
+				throw new InvalidDataException($"Duplicate initializer '{duplicateInit.Key.Name}'");

 			var init = new ActorInitializer(this, initDict);

@@ -142,7 +145,6 @@ namespace OpenRA

 				Info = world.Map.Rules.Actors[name];

-				IPositionable positionable = null;
 				var resolveOrdersList = new List<IResolveOrder>();
 				var renderModifiersList = new List<IRenderModifier>();
 				var rendersList = new List<IRender>();
@@ -164,7 +166,6 @@ namespace OpenRA
 					// performance-sensitive parts of the core game engine, such as pathfinding, visibility and rendering.
 					// Note: The blocks are required to limit the scope of the t's, so we make an exception to our normal style
 					// rules for spacing in order to keep these assignments compact and readable.
-					{ if (trait is IPositionable t) positionable = t; }
 					{ if (trait is IOccupySpace t) OccupiesSpace = t; }
 					{ if (trait is IEffectiveOwner t) EffectiveOwner = t; }
 					{ if (trait is IFacing t) facing = t; }
@@ -191,10 +192,9 @@ namespace OpenRA
 				tickIdles = tickIdlesList.ToArray();
 				Targetables = targetablesList.ToArray();
 				var targetablePositions = targetablePositionsList.ToArray();
-				enabledTargetablePositions = targetablePositions.Where(Exts.IsTraitEnabled);
+				EnabledTargetablePositions = targetablePositions.Where(Exts.IsTraitEnabled);
+				enabledTargetableWorldPositions = EnabledTargetablePositions.SelectMany(tp => tp.TargetablePositions(this));
 				SyncHashes = syncHashesList.ToArray();
-
-				setStaticTargetablePositions = positionable == null && targetablePositions.Any() && targetablePositions.All(tp => tp.AlwaysEnabled);
 			}
 		}

@@ -229,11 +229,6 @@ namespace OpenRA
 			foreach (var notify in allObserverNotifiers)
 				notify(this, readOnlyConditionCache);

-			// All actors that can move or teleport should have IPositionable, if not it's pretty safe to assume the actor is completely immobile and
-			// all targetable positions can be cached if all ITargetablePositions have no conditional requirements.
-			if (setStaticTargetablePositions)
-				staticTargetablePositions = enabledTargetablePositions.SelectMany(tp => tp.TargetablePositions(this)).ToArray();
-
 			// TODO: Other traits may need initialization after being notified of initial condition state.

 			// TODO: A post condition initialization notification phase may allow queueing activities instead.
@@ -246,7 +241,7 @@ namespace OpenRA
 					continue;

 				if (creationActivity != null)
-					throw new InvalidOperationException("More than one enabled ICreationActivity trait: {0} and {1}".F(creationActivity.GetType().Name, ica.GetType().Name));
+					throw new InvalidOperationException($"More than one enabled ICreationActivity trait: {creationActivity.GetType().Name} and {ica.GetType().Name}");

 				var activity = ica.GetCreationActivity();
 				if (activity == null)
@@ -365,8 +360,7 @@ namespace OpenRA

 		public override bool Equals(object obj)
 		{
-			var o = obj as Actor;
-			return o != null && Equals(o);
+			return obj is Actor o && Equals(o);
 		}

 		public bool Equals(Actor other)
@@ -487,7 +481,7 @@ namespace OpenRA
 			health.InflictDamage(this, attacker, damage, false);
 		}

-		public void Kill(Actor attacker, BitSet<DamageType> damageTypes = default(BitSet<DamageType>))
+		public void Kill(Actor attacker, BitSet<DamageType> damageTypes = default)
 		{
 			if (Disposed || health == null)
 				return;
@@ -528,7 +522,7 @@ namespace OpenRA
 		{
 			// PERF: Avoid LINQ.
 			foreach (var targetable in Targetables)
-				if (targetable.IsTraitEnabled() && targetable.TargetableBy(this, byActor))
+				if (targetable.TargetableBy(this, byActor))
 					return true;

 			return false;
@@ -536,11 +530,8 @@ namespace OpenRA

 		public IEnumerable<WPos> GetTargetablePositions()
 		{
-			if (staticTargetablePositions != null)
-				return staticTargetablePositions;
-
-			if (enabledTargetablePositions.Any())
-				return enabledTargetablePositions.SelectMany(tp => tp.TargetablePositions(this));
+			if (EnabledTargetablePositions.Any())
+				return enabledTargetableWorldPositions;

 			return new[] { CenterPosition };
 		}
@@ -549,7 +540,7 @@ namespace OpenRA

 		void UpdateConditionState(string condition, int token, bool isRevoke)
 		{
-			ConditionState conditionState = conditionStates.GetOrAdd(condition);
+			var conditionState = conditionStates.GetOrAdd(condition);

 			if (isRevoke)
 				conditionState.Tokens.Remove(token);
@@ -589,14 +580,14 @@ namespace OpenRA
 		public int RevokeCondition(int token)
 		{
 			if (!conditionTokens.TryGetValue(token, out var condition))
-				throw new InvalidOperationException("Attempting to revoke condition with invalid token {0} for {1}.".F(token, this));
+				throw new InvalidOperationException($"Attempting to revoke condition with invalid token {token} for {this}.");

 			conditionTokens.Remove(token);
 			UpdateConditionState(condition, token, true);
 			return InvalidConditionToken;
 		}

-		/// <summary>Returns whether the specified token is valid for RevokeCondition</summary>
+		/// <summary>Returns whether the specified token is valid for RevokeCondition.</summary>
 		public bool TokenValid(int token)
 		{
 			return conditionTokens.ContainsKey(token);
@@ -609,14 +600,13 @@ namespace OpenRA
 		Lazy<ScriptActorInterface> luaInterface;
 		public void OnScriptBind(ScriptContext context)
 		{
-			if (luaInterface == null)
-				luaInterface = Exts.Lazy(() => new ScriptActorInterface(context, this));
+			luaInterface ??= Exts.Lazy(() => new ScriptActorInterface(context, this));
 		}

 		public LuaValue this[LuaRuntime runtime, LuaValue keyValue]
 		{
-			get { return luaInterface.Value[runtime, keyValue]; }
-			set { luaInterface.Value[runtime, keyValue] = value; }
+			get => luaInterface.Value[runtime, keyValue];
+			set => luaInterface.Value[runtime, keyValue] = value;
 		}

 		public LuaValue Equals(LuaRuntime runtime, LuaValue left, LuaValue right)
@@ -629,7 +619,7 @@ namespace OpenRA

 		public LuaValue ToString(LuaRuntime runtime)
 		{
-			return "Actor ({0})".F(this);
+			return $"Actor ({this})";
 		}

 		public bool HasScriptProperty(string name)
--- a/OpenRA.Game/CPos.cs
+++ b/OpenRA.Game/CPos.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -16,7 +16,7 @@ using OpenRA.Scripting;

 namespace OpenRA
 {
-	public struct CPos : IScriptBindable, ILuaAdditionBinding, ILuaSubtractionBinding, ILuaEqualityBinding, ILuaTableBinding, IEquatable<CPos>
+	public readonly struct CPos : IScriptBindable, ILuaAdditionBinding, ILuaSubtractionBinding, ILuaEqualityBinding, ILuaTableBinding, IEquatable<CPos>
 	{
 		// Coordinates are packed in a 32 bit signed int
 		// X and Y are 12 bits (signed): -2048...2047
@@ -25,13 +25,13 @@ namespace OpenRA
 		public readonly int Bits;

 		// X is padded to MSB, so bit shift does the correct sign extension
-		public int X { get { return Bits >> 20; } }
+		public int X => Bits >> 20;

 		// Align Y with a short, cast, then shift the rest of the way
 		// The signed short bit shift does the correct sign extension
-		public int Y { get { return ((short)(Bits >> 4)) >> 4; } }
+		public int Y => ((short)(Bits >> 4)) >> 4;

-		public byte Layer { get { return (byte)Bits; } }
+		public byte Layer => (byte)Bits;

 		public CPos(int bits) { Bits = bits; }
 		public CPos(int x, int y)
@@ -41,7 +41,7 @@ namespace OpenRA
 			Bits = (x & 0xFFF) << 20 | (y & 0xFFF) << 8 | layer;
 		}

-		public static readonly CPos Zero = new CPos(0, 0, 0);
+		public static readonly CPos Zero = new(0, 0, 0);

 		public static explicit operator CPos(int2 a) { return new CPos(a.X, a.Y); }

@@ -56,9 +56,15 @@ namespace OpenRA
 		public override int GetHashCode() { return Bits.GetHashCode(); }

 		public bool Equals(CPos other) { return Bits == other.Bits; }
-		public override bool Equals(object obj) { return obj is CPos && Equals((CPos)obj); }
+		public override bool Equals(object obj) { return obj is CPos cell && Equals(cell); }

-		public override string ToString() { return X + "," + Y; }
+		public override string ToString()
+		{
+			if (Layer == 0)
+				return X + "," + Y;
+
+			return X + "," + Y + "," + Layer;
+		}

 		public MPos ToMPos(Map map)
 		{
@@ -90,7 +96,7 @@ namespace OpenRA
 		public LuaValue Add(LuaRuntime runtime, LuaValue left, LuaValue right)
 		{
 			if (!left.TryGetClrValue(out CPos a) || !right.TryGetClrValue(out CVec b))
-				throw new LuaException("Attempted to call CPos.Add(CPos, CVec) with invalid arguments ({0}, {1})".F(left.WrappedClrType().Name, right.WrappedClrType().Name));
+				throw new LuaException($"Attempted to call CPos.Add(CPos, CVec) with invalid arguments ({left.WrappedClrType().Name}, {right.WrappedClrType().Name})");

 			return new LuaCustomClrObject(a + b);
 		}
@@ -99,7 +105,7 @@ namespace OpenRA
 		{
 			var rightType = right.WrappedClrType();
 			if (!left.TryGetClrValue(out CPos a))
-				throw new LuaException("Attempted to call CPos.Subtract(CPos, (CPos|CVec)) with invalid arguments ({0}, {1})".F(left.WrappedClrType().Name, rightType.Name));
+				throw new LuaException($"Attempted to call CPos.Subtract(CPos, (CPos|CVec)) with invalid arguments ({left.WrappedClrType().Name}, {rightType.Name})");

 			if (rightType == typeof(CPos))
 			{
@@ -112,7 +118,7 @@ namespace OpenRA
 				return new LuaCustomClrObject(a - b);
 			}

-			throw new LuaException("Attempted to call CPos.Subtract(CPos, (CPos|CVec)) with invalid arguments ({0}, {1})".F(left.WrappedClrType().Name, rightType.Name));
+			throw new LuaException($"Attempted to call CPos.Subtract(CPos, (CPos|CVec)) with invalid arguments ({left.WrappedClrType().Name}, {rightType.Name})");
 		}

 		public LuaValue Equals(LuaRuntime runtime, LuaValue left, LuaValue right)
@@ -132,14 +138,11 @@ namespace OpenRA
 					case "X": return X;
 					case "Y": return Y;
 					case "Layer": return Layer;
-					default: throw new LuaException("CPos does not define a member '{0}'".F(key));
+					default: throw new LuaException($"CPos does not define a member '{key}'");
 				}
 			}

-			set
-			{
-				throw new LuaException("CPos is read-only. Use CPos.New to create a new value");
-			}
+			set => throw new LuaException("CPos is read-only. Use CPos.New to create a new value");
 		}

 		#endregion
--- a/OpenRA.Game/CVec.cs
+++ b/OpenRA.Game/CVec.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -17,12 +17,12 @@ using OpenRA.Scripting;

 namespace OpenRA
 {
-	public struct CVec : IScriptBindable, ILuaAdditionBinding, ILuaSubtractionBinding, ILuaUnaryMinusBinding, ILuaEqualityBinding, ILuaTableBinding, IEquatable<CVec>
+	public readonly struct CVec : IScriptBindable, ILuaAdditionBinding, ILuaSubtractionBinding, ILuaUnaryMinusBinding, ILuaEqualityBinding, ILuaTableBinding, IEquatable<CVec>
 	{
 		public readonly int X, Y;

 		public CVec(int x, int y) { X = x; Y = y; }
-		public static readonly CVec Zero = new CVec(0, 0);
+		public static readonly CVec Zero = new(0, 0);

 		public static CVec operator +(CVec a, CVec b) { return new CVec(a.X + b.X, a.Y + b.Y); }
 		public static CVec operator -(CVec a, CVec b) { return new CVec(a.X - b.X, a.Y - b.Y); }
@@ -42,8 +42,8 @@ namespace OpenRA

 		public CVec Sign() { return new CVec(Math.Sign(X), Math.Sign(Y)); }
 		public CVec Abs() { return new CVec(Math.Abs(X), Math.Abs(Y)); }
-		public int LengthSquared { get { return X * X + Y * Y; } }
-		public int Length { get { return Exts.ISqrt(LengthSquared); } }
+		public int LengthSquared => X * X + Y * Y;
+		public int Length => Exts.ISqrt(LengthSquared);

 		public CVec Clamp(Rectangle r)
 		{
@@ -55,7 +55,7 @@ namespace OpenRA
 		public override int GetHashCode() { return X.GetHashCode() ^ Y.GetHashCode(); }

 		public bool Equals(CVec other) { return other == this; }
-		public override bool Equals(object obj) { return obj is CVec && Equals((CVec)obj); }
+		public override bool Equals(object obj) { return obj is CVec vec && Equals(vec); }

 		public override string ToString() { return X + "," + Y; }

@@ -76,7 +76,7 @@ namespace OpenRA
 		public LuaValue Add(LuaRuntime runtime, LuaValue left, LuaValue right)
 		{
 			if (!left.TryGetClrValue(out CVec a) || !right.TryGetClrValue(out CVec b))
-				throw new LuaException("Attempted to call CVec.Add(CVec, CVec) with invalid arguments ({0}, {1})".F(left.WrappedClrType().Name, right.WrappedClrType().Name));
+				throw new LuaException($"Attempted to call CVec.Add(CVec, CVec) with invalid arguments ({left.WrappedClrType().Name}, {right.WrappedClrType().Name})");

 			return new LuaCustomClrObject(a + b);
 		}
@@ -84,7 +84,7 @@ namespace OpenRA
 		public LuaValue Subtract(LuaRuntime runtime, LuaValue left, LuaValue right)
 		{
 			if (!left.TryGetClrValue(out CVec a) || !right.TryGetClrValue(out CVec b))
-				throw new LuaException("Attempted to call CVec.Subtract(CVec, CVec) with invalid arguments ({0}, {1})".F(left.WrappedClrType().Name, right.WrappedClrType().Name));
+				throw new LuaException($"Attempted to call CVec.Subtract(CVec, CVec) with invalid arguments ({left.WrappedClrType().Name}, {right.WrappedClrType().Name})");

 			return new LuaCustomClrObject(a - b);
 		}
@@ -110,14 +110,11 @@ namespace OpenRA
 				{
 					case "X": return X;
 					case "Y": return Y;
-					default: throw new LuaException("CVec does not define a member '{0}'".F(key));
+					default: throw new LuaException($"CVec does not define a member '{key}'");
 				}
 			}

-			set
-			{
-				throw new LuaException("CVec is read-only. Use CVec.New to create a new value");
-			}
+			set => throw new LuaException("CVec is read-only. Use CVec.New to create a new value");
 		}

 		#endregion
--- a/OpenRA.Game/CryptoUtil.cs
+++ b/OpenRA.Game/CryptoUtil.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -187,8 +187,10 @@ namespace OpenRA
 			}
 			catch (Exception e)
 			{
-				Log.Write("debug", "Failed to decrypt string with exception: {0}", e);
-				Console.WriteLine("String decryption failed: {0}", e);
+				Log.Write("debug", "Failed to decrypt string with exception:");
+				Log.Write("debug", e);
+				Console.WriteLine("String decryption failed:");
+				Console.WriteLine(e);
 				return null;
 			}
 		}
@@ -211,8 +213,10 @@ namespace OpenRA
 			}
 			catch (Exception e)
 			{
-				Log.Write("debug", "Failed to sign string with exception: {0}", e);
-				Console.WriteLine("String signing failed: {0}", e);
+				Log.Write("debug", "Failed to sign string with exception");
+				Log.Write("debug", e);
+				Console.WriteLine("String signing failed:");
+				Console.WriteLine(e);
 				return null;
 			}
 		}
@@ -235,8 +239,10 @@ namespace OpenRA
 			}
 			catch (Exception e)
 			{
-				Log.Write("debug", "Failed to verify signature with exception: {0}", e);
-				Console.WriteLine("Signature validation failed: {0}", e);
+				Log.Write("debug", "Failed to verify signature with exception:");
+				Log.Write("debug", e);
+				Console.WriteLine("Signature validation failed:");
+				Console.WriteLine(e);
 				return false;
 			}
 		}
--- a/OpenRA.Game/DefaultPlayer.cs
+++ b/OpenRA.Game/DefaultPlayer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -15,6 +15,6 @@ namespace OpenRA
 {
 	public class DefaultPlayer : IGlobalModData
 	{
-		public readonly Color Color = Color.FromAhsl(0, 0, 238);
+		public readonly Color Color = Color.FromArgb(0xEE, 0xEE, 0xEE);
 	}
 }
--- a/OpenRA.Game/Download.cs
+++ b/OpenRA.Game/Download.cs
@@ -1,96 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-using System;
-using System.ComponentModel;
-using System.Net;
-
-namespace OpenRA
-{
-	public class Download
-	{
-		readonly object syncObject = new object();
-		WebClient wc;
-
-		public static string FormatErrorMessage(Exception e)
-		{
-			var ex = e as WebException;
-			if (ex == null)
-				return e.Message;
-
-			switch (ex.Status)
-			{
-				case WebExceptionStatus.RequestCanceled:
-					return "Cancelled";
-				case WebExceptionStatus.NameResolutionFailure:
-					return "DNS lookup failed";
-				case WebExceptionStatus.Timeout:
-					return "Connection timeout";
-				case WebExceptionStatus.ConnectFailure:
-					return "Cannot connect to remote server";
-				case WebExceptionStatus.ProtocolError:
-					return "File not found on remote server";
-				default:
-					return ex.Message;
-			}
-		}
-
-		void EnableTLS12OnWindows()
-		{
-			// Enable TLS 1.2 on Windows: .NET 4.7 on Windows 10 only supports obsolete protocols by default
-			// SecurityProtocolType.Tls12 is not defined in the .NET 4.5 reference dlls used by mono,
-			// so we must use the enum's constant value directly
-			if (Platform.CurrentPlatform == PlatformType.Windows)
-				ServicePointManager.SecurityProtocol |= (SecurityProtocolType)3072;
-		}
-
-		public Download(string url, string path, Action<DownloadProgressChangedEventArgs> onProgress, Action<AsyncCompletedEventArgs> onComplete)
-		{
-			EnableTLS12OnWindows();
-
-			lock (syncObject)
-			{
-				wc = new WebClient { Proxy = null };
-				wc.DownloadProgressChanged += (_, a) => onProgress(a);
-				wc.DownloadFileCompleted += (_, a) => { DisposeWebClient(); onComplete(a); };
-				wc.DownloadFileAsync(new Uri(url), path);
-			}
-		}
-
-		public Download(string url, Action<DownloadProgressChangedEventArgs> onProgress, Action<DownloadDataCompletedEventArgs> onComplete)
-		{
-			EnableTLS12OnWindows();
-
-			lock (syncObject)
-			{
-				wc = new WebClient { Proxy = null };
-				wc.DownloadProgressChanged += (_, a) => onProgress(a);
-				wc.DownloadDataCompleted += (_, a) => { DisposeWebClient(); onComplete(a); };
-				wc.DownloadDataAsync(new Uri(url));
-			}
-		}
-
-		void DisposeWebClient()
-		{
-			lock (syncObject)
-			{
-				wc.Dispose();
-				wc = null;
-			}
-		}
-
-		public void CancelAsync()
-		{
-			lock (syncObject)
-				wc?.CancelAsync();
-		}
-	}
-}
--- a/OpenRA.Game/Effects/AsyncAction.cs
+++ b/OpenRA.Game/Effects/AsyncAction.cs
@@ -1,39 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-using System;
-using System.Collections.Generic;
-using OpenRA.Graphics;
-
-namespace OpenRA.Effects
-{
-	public class AsyncAction : IEffect
-	{
-		Action a;
-		IAsyncResult ar;
-
-		public AsyncAction(IAsyncResult ar, Action a)
-		{
-			this.a = a;
-			this.ar = ar;
-		}
-
-		public void Tick(World world)
-		{
-			if (ar.IsCompleted)
-			{
-				world.AddFrameEndTask(w => { w.Remove(this); a(); });
-			}
-		}
-
-		public IEnumerable<IRenderable> Render(WorldRenderer r) { yield break; }
-	}
-}
--- a/OpenRA.Game/Effects/DelayedAction.cs
+++ b/OpenRA.Game/Effects/DelayedAction.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -17,7 +17,7 @@ namespace OpenRA.Effects
 {
 	public class DelayedAction : IEffect
 	{
-		Action a;
+		readonly Action a;
 		int delay;

 		public DelayedAction(int delay, Action a)
--- a/OpenRA.Game/Effects/DelayedImpact.cs
+++ b/OpenRA.Game/Effects/DelayedImpact.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
--- a/OpenRA.Game/Effects/IEffect.cs
+++ b/OpenRA.Game/Effects/IEffect.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
--- a/OpenRA.Game/ExternalMods.cs
+++ b/OpenRA.Game/ExternalMods.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -41,7 +41,7 @@ namespace OpenRA

 	public class ExternalMods : IReadOnlyDictionary<string, ExternalMod>
 	{
-		readonly Dictionary<string, ExternalMod> mods = new Dictionary<string, ExternalMod>();
+		readonly Dictionary<string, ExternalMod> mods = new();
 		readonly SheetBuilder sheetBuilder;

 		Sheet CreateSheet()
@@ -66,12 +66,7 @@ namespace OpenRA
 			// Several types of support directory types are available, depending on
 			// how the player has installed and launched the game.
 			// Read registration metadata from all of them
-			var sources = Enum.GetValues(typeof(SupportDirType))
-				.Cast<SupportDirType>()
-				.Select(t => Platform.GetSupportDir(t))
-				.Distinct();
-
-			foreach (var source in sources)
+			foreach (var source in GetSupportDirs(ModRegistration.User | ModRegistration.System))
 			{
 				var metadataPath = Path.Combine(source, "ModMetadata");
 				if (!Directory.Exists(metadataPath))
@@ -86,8 +81,8 @@ namespace OpenRA
 					}
 					catch (Exception e)
 					{
-						Log.Write("debug", "Failed to parse mod metadata file '{0}'", path);
-						Log.Write("debug", e.ToString());
+						Log.Write("debug", $"Failed to parse mod metadata file '{path}'");
+						Log.Write("debug", e);
 					}
 				}
 			}
@@ -148,7 +143,7 @@ namespace OpenRA
 				if (stream != null)
 					yaml.Value.Nodes.Add(new MiniYamlNode("Icon3x", Convert.ToBase64String(stream.ReadAllBytes())));

-			var sources = new List<string>();
+			var sources = new HashSet<string>();
 			if (registration.HasFlag(ModRegistration.System))
 				sources.Add(Platform.GetSupportDir(SupportDirType.System));

@@ -167,7 +162,7 @@ namespace OpenRA
 			LoadMod(yaml.Value, forceRegistration: true);

 			var lines = new List<MiniYamlNode> { yaml }.ToLines().ToArray();
-			foreach (var source in sources.Distinct())
+			foreach (var source in sources)
 			{
 				var metadataPath = Path.Combine(source, "ModMetadata");

@@ -179,35 +174,23 @@ namespace OpenRA
 				catch (Exception e)
 				{
 					Log.Write("debug", "Failed to register current mod metadata");
-					Log.Write("debug", e.ToString());
+					Log.Write("debug", e);
 				}
 			}
 		}

 		/// <summary>
 		/// Removes invalid mod registrations:
-		/// * LaunchPath no longer exists
-		/// * LaunchPath and mod id matches the active mod, but the version is different
-		/// * Filename doesn't match internal key
-		/// * Fails to parse as a mod registration
+		/// <list type="bullet">
+		/// <item>LaunchPath no longer exists.</item>
+		/// <item>LaunchPath and mod id matches the active mod, but the version is different.</item>
+		/// <item>Filename doesn't match internal key.</item>
+		/// <item>Fails to parse as a mod registration.</item>
+		/// </list>
 		/// </summary>
-		internal void ClearInvalidRegistrations(ExternalMod activeMod, ModRegistration registration)
+		internal void ClearInvalidRegistrations(ModRegistration registration)
 		{
-			var sources = new List<string>();
-			if (registration.HasFlag(ModRegistration.System))
-				sources.Add(Platform.GetSupportDir(SupportDirType.System));
-
-			if (registration.HasFlag(ModRegistration.User))
-			{
-				// User support dir may be using the modern or legacy value, or overridden by the user
-				// Add all the possibilities and let the .Distinct() below ignore the duplicates
-				sources.Add(Platform.GetSupportDir(SupportDirType.User));
-				sources.Add(Platform.GetSupportDir(SupportDirType.ModernUser));
-				sources.Add(Platform.GetSupportDir(SupportDirType.LegacyUser));
-			}
-
-			var activeModKey = ExternalMod.MakeKey(activeMod);
-			foreach (var source in sources.Distinct())
+			foreach (var source in GetSupportDirs(registration))
 			{
 				var metadataPath = Path.Combine(source, "ModMetadata");
 				if (!Directory.Exists(metadataPath))
@@ -222,19 +205,16 @@ namespace OpenRA
 						var m = FieldLoader.Load<ExternalMod>(yaml);
 						modKey = ExternalMod.MakeKey(m);

-						// Continue to the next entry if it is the active mod (even if the LaunchPath is bogus)
-						if (modKey == activeModKey)
-							continue;
-
 						// Continue to the next entry if this one is valid
-						if (File.Exists(m.LaunchPath) && Path.GetFileNameWithoutExtension(path) == modKey &&
-							!(activeMod != null && m.LaunchPath == activeMod.LaunchPath && m.Id == activeMod.Id && m.Version != activeMod.Version))
+						// HACK: Explicitly invalidate paths to OpenRA.dll to clean up bogus metadata files
+						// that were created after the initial migration from .NET Framework to Core/5.
+						if (File.Exists(m.LaunchPath) && Path.GetFileNameWithoutExtension(path) == modKey && Path.GetExtension(m.LaunchPath) != ".dll")
 							continue;
 					}
 					catch (Exception e)
 					{
-						Log.Write("debug", "Failed to parse mod metadata file '{0}'", path);
-						Log.Write("debug", e.ToString());
+						Log.Write("debug", $"Failed to parse mod metadata file '{path}'");
+						Log.Write("debug", e);
 					}

 					// Remove from the ingame mod switcher
@@ -245,12 +225,12 @@ namespace OpenRA
 					try
 					{
 						File.Delete(path);
-						Log.Write("debug", "Removed invalid mod metadata file '{0}'", path);
+						Log.Write("debug", $"Removed invalid mod metadata file '{path}'");
 					}
 					catch (Exception e)
 					{
-						Log.Write("debug", "Failed to remove mod metadata file '{0}'", path);
-						Log.Write("debug", e.ToString());
+						Log.Write("debug", $"Failed to remove mod metadata file '{path}'");
+						Log.Write("debug", e);
 					}
 				}
 			}
@@ -258,23 +238,10 @@ namespace OpenRA

 		internal void Unregister(Manifest mod, ModRegistration registration)
 		{
-			var sources = new List<string>();
-			if (registration.HasFlag(ModRegistration.System))
-				sources.Add(Platform.GetSupportDir(SupportDirType.System));
-
-			if (registration.HasFlag(ModRegistration.User))
-			{
-				// User support dir may be using the modern or legacy value, or overridden by the user
-				// Add all the possibilities and let the .Distinct() below ignore the duplicates
-				sources.Add(Platform.GetSupportDir(SupportDirType.User));
-				sources.Add(Platform.GetSupportDir(SupportDirType.ModernUser));
-				sources.Add(Platform.GetSupportDir(SupportDirType.LegacyUser));
-			}
-
 			var key = ExternalMod.MakeKey(mod);
 			mods.Remove(key);

-			foreach (var source in sources.Distinct())
+			foreach (var source in GetSupportDirs(registration))
 			{
 				var path = Path.Combine(source, "ModMetadata", key + ".yaml");
 				try
@@ -284,16 +251,39 @@ namespace OpenRA
 				}
 				catch (Exception e)
 				{
-					Log.Write("debug", "Failed to remove mod metadata file '{0}'", path);
-					Log.Write("debug", e.ToString());
+					Log.Write("debug", $"Failed to remove mod metadata file '{path}'");
+					Log.Write("debug", e);
 				}
 			}
 		}

-		public ExternalMod this[string key] { get { return mods[key]; } }
-		public int Count { get { return mods.Count; } }
-		public ICollection<string> Keys { get { return mods.Keys; } }
-		public ICollection<ExternalMod> Values { get { return mods.Values; } }
+		static IEnumerable<string> GetSupportDirs(ModRegistration registration)
+		{
+			var sources = new HashSet<string>(4);
+			if (registration.HasFlag(ModRegistration.System))
+				sources.Add(Platform.GetSupportDir(SupportDirType.System));
+
+			if (registration.HasFlag(ModRegistration.User))
+			{
+				// User support dir may be using the modern or legacy value, or overridden by the user
+				// Add all the possibilities and let the HashSet ignore the duplicates
+				sources.Add(Platform.GetSupportDir(SupportDirType.User));
+				sources.Add(Platform.GetSupportDir(SupportDirType.ModernUser));
+				sources.Add(Platform.GetSupportDir(SupportDirType.LegacyUser));
+			}
+
+			return sources;
+		}
+
+		public ExternalMod this[string key] => mods[key];
+		public int Count => mods.Count;
+		public ICollection<string> Keys => mods.Keys;
+		public ICollection<ExternalMod> Values => mods.Values;
+
+		IEnumerable<string> IReadOnlyDictionary<string, ExternalMod>.Keys => ((IReadOnlyDictionary<string, ExternalMod>)mods).Keys;
+
+		IEnumerable<ExternalMod> IReadOnlyDictionary<string, ExternalMod>.Values => ((IReadOnlyDictionary<string, ExternalMod>)mods).Values;
+
 		public bool ContainsKey(string key) { return mods.ContainsKey(key); }
 		public IEnumerator<KeyValuePair<string, ExternalMod>> GetEnumerator() { return mods.GetEnumerator(); }
 		public bool TryGetValue(string key, out ExternalMod value) { return mods.TryGetValue(key, out value); }
--- a/OpenRA.Game/Exts.cs
+++ b/OpenRA.Game/Exts.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -27,23 +27,12 @@ namespace OpenRA
 			return string.Compare(str.ToUpperInvariant(), str, false) == 0;
 		}

-		public static string F(this string fmt, params object[] args)
-		{
-			return string.Format(fmt, args);
-		}
-
 		public static T WithDefault<T>(T def, Func<T> f)
 		{
 			try { return f(); }
 			catch { return def; }
 		}

-		public static void Do<T>(this IEnumerable<T> e, Action<T> fn)
-		{
-			foreach (var ee in e)
-				fn(ee);
-		}
-
 		public static Lazy<T> Lazy<T>(Func<T> p) { return new Lazy<T>(p); }

 		public static IEnumerable<string> GetNamespaces(this Assembly a)
@@ -51,21 +40,16 @@ namespace OpenRA
 			return a.GetTypes().Select(t => t.Namespace).Distinct().Where(n => n != null);
 		}

-		public static bool HasAttribute<T>(this MemberInfo mi)
+		public static bool HasAttribute<TAttribute>(this MemberInfo mi)
+			where TAttribute : Attribute
 		{
-			return mi.GetCustomAttributes(typeof(T), true).Length != 0;
+			return Attribute.IsDefined(mi, typeof(TAttribute));
 		}

-		public static T[] GetCustomAttributes<T>(this MemberInfo mi, bool inherit)
-			where T : class
+		public static TAttribute[] GetCustomAttributes<TAttribute>(this MemberInfo mi, bool inherit)
+			where TAttribute : Attribute
 		{
-			return (T[])mi.GetCustomAttributes(typeof(T), inherit);
-		}
-
-		public static T[] GetCustomAttributes<T>(this ParameterInfo mi)
-			where T : class
-		{
-			return (T[])mi.GetCustomAttributes(typeof(T), true);
+			return (TAttribute[])mi.GetCustomAttributes(typeof(TAttribute), inherit);
 		}

 		public static T Clamp<T>(this T val, T min, T max) where T : IComparable<T>
@@ -107,7 +91,7 @@ namespace OpenRA
 			//  - the triangles ACD and BCD must have opposite sense (clockwise or anticlockwise)
 			//  - the triangles CAB and DAB must have opposite sense
 			// Segments intersect if the orientation (clockwise or anticlockwise) of the two points in each line segment are opposite with respect to the other
-			// Assumes that lines are not colinear
+			// Assumes that lines are not collinear
 			return WindingDirectionTest(c, d, a) != WindingDirectionTest(c, d, b) && WindingDirectionTest(a, b, c) != WindingDirectionTest(a, b, d);
 		}

@@ -125,13 +109,23 @@ namespace OpenRA

 		public static V GetOrAdd<K, V>(this Dictionary<K, V> d, K k, V v)
 		{
+#if NET5_0_OR_GREATER
+			// SAFETY: Dictionary cannot be modified whilst the ref is alive.
+			ref var value = ref System.Runtime.InteropServices.CollectionsMarshal.GetValueRefOrAddDefault(d, k, out var exists);
+			if (!exists)
+				value = v;
+			return value;
+#else
 			if (!d.TryGetValue(k, out var ret))
 				d.Add(k, ret = v);
 			return ret;
+#endif
 		}

 		public static V GetOrAdd<K, V>(this Dictionary<K, V> d, K k, Func<K, V> createFn)
 		{
+			// Cannot use CollectionsMarshal.GetValueRefOrAddDefault here,
+			// the creation function could mutate the dictionary which would invalidate the ref.
 			if (!d.TryGetValue(k, out var ret))
 				d.Add(k, ret = createFn(k));
 			return ret;
@@ -155,13 +149,13 @@ namespace OpenRA
 		static T Random<T>(IEnumerable<T> ts, MersenneTwister r, bool throws)
 		{
 			var xs = ts as ICollection<T>;
-			xs = xs ?? ts.ToList();
+			xs ??= ts.ToList();
 			if (xs.Count == 0)
 			{
 				if (throws)
-					throw new ArgumentException("Collection must not be empty.", "ts");
+					throw new ArgumentException("Collection must not be empty.", nameof(ts));
 				else
-					return default(T);
+					return default;
 			}
 			else
 				return xs.ElementAt(r.Next(xs.Count));
@@ -236,9 +230,9 @@ namespace OpenRA
 			{
 				if (!e.MoveNext())
 					if (throws)
-						throw new ArgumentException("Collection must not be empty.", "ts");
+						throw new ArgumentException("Collection must not be empty.", nameof(ts));
 					else
-						return default(T);
+						return default;
 				t = e.Current;
 				u = selector(t);
 				while (e.MoveNext())
@@ -278,7 +272,7 @@ namespace OpenRA
 		public static int ISqrt(int number, ISqrtRoundMode round = ISqrtRoundMode.Floor)
 		{
 			if (number < 0)
-				throw new InvalidOperationException("Attempted to calculate the square root of a negative integer: {0}".F(number));
+				throw new InvalidOperationException($"Attempted to calculate the square root of a negative integer: {number}");

 			return (int)ISqrt((uint)number, round);
 		}
@@ -319,7 +313,7 @@ namespace OpenRA
 		public static long ISqrt(long number, ISqrtRoundMode round = ISqrtRoundMode.Floor)
 		{
 			if (number < 0)
-				throw new InvalidOperationException("Attempted to calculate the square root of a negative integer: {0}".F(number));
+				throw new InvalidOperationException($"Attempted to calculate the square root of a negative integer: {number}");

 			return (long)ISqrt((ulong)number, round);
 		}
@@ -357,6 +351,11 @@ namespace OpenRA
 			return root;
 		}

+		public static int MultiplyBySqrtTwo(short number)
+		{
+			return number * 46341 / 32768;
+		}
+
 		public static int IntegerDivisionRoundingAwayFromZero(int dividend, int divisor)
 		{
 			var quotient = Math.DivRem(dividend, divisor, out var remainder);
@@ -375,6 +374,11 @@ namespace OpenRA
 			return ts.Concat(moreTs);
 		}

+		public static IEnumerable<T> Exclude<T>(this IEnumerable<T> ts, params T[] exclusions)
+		{
+			return ts.Except(exclusions);
+		}
+
 		public static HashSet<T> ToHashSet<T>(this IEnumerable<T> source)
 		{
 			return new HashSet<T>(source);
@@ -392,12 +396,13 @@ namespace OpenRA
 			string debugName, Func<TKey, string> logKey = null, Func<TElement, string> logValue = null)
 		{
 			// Fall back on ToString() if null functions are provided:
-			logKey = logKey ?? (s => s.ToString());
-			logValue = logValue ?? (s => s.ToString());
+			logKey ??= s => s.ToString();
+			logValue ??= s => s.ToString();

 			// Try to build a dictionary and log all duplicates found (if any):
 			var dupKeys = new Dictionary<TKey, List<string>>();
-			var d = new Dictionary<TKey, TElement>();
+			var capacity = source is ICollection<TSource> collection ? collection.Count : 0;
+			var d = new Dictionary<TKey, TElement>(capacity);
 			foreach (var item in source)
 			{
 				var key = keySelector(item);
@@ -408,29 +413,28 @@ namespace OpenRA
 					continue;

 				// Check for a key conflict:
-				if (d.ContainsKey(key))
+				if (!d.TryAdd(key, element))
 				{
 					if (!dupKeys.TryGetValue(key, out var dupKeyMessages))
 					{
 						// Log the initial conflicting value already inserted:
-						dupKeyMessages = new List<string>();
-						dupKeyMessages.Add(logValue(d[key]));
+						dupKeyMessages = new List<string>
+						{
+							logValue(d[key])
+						};
 						dupKeys.Add(key, dupKeyMessages);
 					}

 					// Log this conflicting value:
 					dupKeyMessages.Add(logValue(element));
-					continue;
 				}
-
-				d.Add(key, element);
 			}

 			// If any duplicates were found, throw a descriptive error
 			if (dupKeys.Count > 0)
 			{
-				var badKeysFormatted = string.Join(", ", dupKeys.Select(p => "{0}: [{1}]".F(logKey(p.Key), string.Join(",", p.Value))));
-				var msg = "{0}, duplicate values found for the following keys: {1}".F(debugName, badKeysFormatted);
+				var badKeysFormatted = string.Join(", ", dupKeys.Select(p => $"{logKey(p.Key)}: [{string.Join(",", p.Value)}]"));
+				var msg = $"{debugName}, duplicate values found for the following keys: {badKeysFormatted}";
 				throw new ArgumentException(msg);
 			}

@@ -511,8 +515,7 @@ namespace OpenRA

 		public static bool IsTraitEnabled<T>(this T trait)
 		{
-			var disabledTrait = trait as IDisabledTrait;
-			return disabledTrait == null || !disabledTrait.IsTraitDisabled;
+			return trait is not IDisabledTrait disabledTrait || !disabledTrait.IsTraitDisabled;
 		}

 		public static T FirstEnabledTraitOrDefault<T>(this IEnumerable<T> ts)
@@ -522,7 +525,7 @@ namespace OpenRA
 				if (t.IsTraitEnabled())
 					return t;

-			return default(T);
+			return default;
 		}

 		public static T FirstEnabledTraitOrDefault<T>(this T[] ts)
@@ -532,8 +535,72 @@ namespace OpenRA
 				if (t.IsTraitEnabled())
 					return t;

-			return default(T);
+			return default;
 		}
+
+		public static T FirstEnabledConditionalTraitOrDefault<T>(this IEnumerable<T> ts) where T : IDisabledTrait
+		{
+			// PERF: Avoid LINQ.
+			foreach (var t in ts)
+				if (!t.IsTraitDisabled)
+					return t;
+
+			return default;
+		}
+
+		public static T FirstEnabledConditionalTraitOrDefault<T>(this T[] ts) where T : IDisabledTrait
+		{
+			// PERF: Avoid LINQ.
+			foreach (var t in ts)
+				if (!t.IsTraitDisabled)
+					return t;
+
+			return default;
+		}
+
+		public static LineSplitEnumerator SplitLines(this string str, char separator)
+		{
+			return new LineSplitEnumerator(str.AsSpan(), separator);
+		}
+	}
+
+	public ref struct LineSplitEnumerator
+	{
+		ReadOnlySpan<char> str;
+		readonly char separator;
+
+		public LineSplitEnumerator(ReadOnlySpan<char> str, char separator)
+		{
+			this.str = str;
+			this.separator = separator;
+			Current = default;
+		}
+
+		public LineSplitEnumerator GetEnumerator() => this;
+
+		public bool MoveNext()
+		{
+			var span = str;
+
+			// Reach the end of the string
+			if (span.Length == 0)
+				return false;
+
+			var index = span.IndexOf(separator);
+			if (index == -1)
+			{
+				// The remaining string is an empty string
+				str = ReadOnlySpan<char>.Empty;
+				Current = span;
+				return true;
+			}
+
+			Current = span[..index];
+			str = span[(index + 1)..];
+			return true;
+		}
+
+		public ReadOnlySpan<char> Current { get; private set; }
 	}

 	public static class Enum<T>
@@ -549,7 +616,7 @@ namespace OpenRA

 			if (values.Any(x => !names.Contains(x)))
 			{
-				value = default(T);
+				value = default;
 				return false;
 			}

--- a/OpenRA.Game/FieldLoader.cs
+++ b/OpenRA.Game/FieldLoader.cs
--- a/OpenRA.Game/FieldSaver.cs
+++ b/OpenRA.Game/FieldSaver.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -72,32 +72,14 @@ namespace OpenRA
 				return "";

 			var t = v.GetType();
-
-			if (t == typeof(Color))
-			{
-				return ((Color)v).ToString();
-			}
-
-			if (t == typeof(Rectangle))
-			{
-				var r = (Rectangle)v;
-				return "{0},{1},{2},{3}".F(r.X, r.Y, r.Width, r.Height);
-			}
-
 			if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(BitSet<>))
-			{
 				return ((IEnumerable<string>)v).Select(FormatValue).JoinWith(", ");
-			}

 			if (t.IsArray && t.GetArrayRank() == 1)
-			{
 				return ((Array)v).Cast<object>().Select(FormatValue).JoinWith(", ");
-			}

 			if (t.IsGenericType && (t.GetGenericTypeDefinition() == typeof(HashSet<>) || t.GetGenericTypeDefinition() == typeof(List<>)))
-			{
 				return ((System.Collections.IEnumerable)v).Cast<object>().Select(FormatValue).JoinWith(", ");
-			}

 			// This is only for documentation generation
 			if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Dictionary<,>))
@@ -112,17 +94,14 @@ namespace OpenRA
 					var formattedKey = FormatValue(key);
 					var formattedValue = FormatValue(value);

-					result += "{0}: {1}{2}".F(formattedKey, formattedValue, Environment.NewLine);
+					result += $"{formattedKey}: {formattedValue}{Environment.NewLine}";
 				}

 				return result;
 			}

-			if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Primitives.Cache<,>))
-				return ""; // TODO
-
-			if (t == typeof(DateTime))
-				return ((DateTime)v).ToString("yyyy-MM-dd HH-mm-ss", CultureInfo.InvariantCulture);
+			if (v is DateTime d)
+				return d.ToString("yyyy-MM-dd HH-mm-ss", CultureInfo.InvariantCulture);

 			// Try the TypeConverter
 			var conv = TypeDescriptor.GetConverter(t);
--- a/OpenRA.Game/FileFormats/Png.cs
+++ b/OpenRA.Game/FileFormats/Png.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -17,6 +17,7 @@ using System.Net;
 using System.Text;
 using ICSharpCode.SharpZipLib.Checksum;
 using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
+using OpenRA.Graphics;
 using OpenRA.Primitives;

 namespace OpenRA.FileFormats
@@ -25,11 +26,14 @@ namespace OpenRA.FileFormats
 	{
 		static readonly byte[] Signature = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };

-		public int Width { get; set; }
-		public int Height { get; set; }
-		public Color[] Palette { get; set; }
-		public byte[] Data { get; set; }
-		public Dictionary<string, string> EmbeddedData = new Dictionary<string, string>();
+		public int Width { get; }
+		public int Height { get; }
+		public Color[] Palette { get; }
+		public byte[] Data { get; }
+		public SpriteFrameType Type { get; }
+		public Dictionary<string, string> EmbeddedData = new();
+
+		public int PixelStride => Type == SpriteFrameType.Indexed8 ? 1 : Type == SpriteFrameType.Rgb24 ? 3 : 4;

 		public Png(Stream s)
 		{
@@ -38,9 +42,8 @@ namespace OpenRA.FileFormats

 			s.Position += 8;
 			var headerParsed = false;
-			var isPaletted = false;
-			var is24Bit = false;
 			var data = new List<byte>();
+			Type = SpriteFrameType.Rgba32;

 			while (true)
 			{
@@ -64,19 +67,17 @@ namespace OpenRA.FileFormats
 							Height = IPAddress.NetworkToHostOrder(ms.ReadInt32());

 							var bitDepth = ms.ReadUInt8();
-							var colorType = (PngColorType)ms.ReadByte();
-							isPaletted = IsPaletted(bitDepth, colorType);
-							is24Bit = colorType == PngColorType.Color;
+							var colorType = (PngColorType)ms.ReadUInt8();
+							if (IsPaletted(bitDepth, colorType))
+								Type = SpriteFrameType.Indexed8;
+							else if (colorType == PngColorType.Color)
+								Type = SpriteFrameType.Rgb24;

-							var dataLength = Width * Height;
-							if (!isPaletted)
-								dataLength *= 4;
+							Data = new byte[Width * Height * PixelStride];

-							Data = new byte[dataLength];
-
-							var compression = ms.ReadByte();
-							/*var filter = */ms.ReadByte();
-							var interlace = ms.ReadByte();
+							var compression = ms.ReadUInt8();
+							/*var filter = */ms.ReadUInt8();
+							var interlace = ms.ReadUInt8();

 							if (compression != 0)
 								throw new InvalidDataException("Compression method not supported");
@@ -94,7 +95,7 @@ namespace OpenRA.FileFormats
 							Palette = new Color[256];
 							for (var i = 0; i < length / 3; i++)
 							{
-								var r = ms.ReadByte(); var g = ms.ReadByte(); var b = ms.ReadByte();
+								var r = ms.ReadUInt8(); var g = ms.ReadUInt8(); var b = ms.ReadUInt8();
 								Palette[i] = Color.FromArgb(r, g, b);
 							}

@@ -107,7 +108,7 @@ namespace OpenRA.FileFormats
 								throw new InvalidDataException("Non-Palette indexed PNG are not supported.");

 							for (var i = 0; i < length; i++)
-								Palette[i] = Color.FromArgb(ms.ReadByte(), Palette[i]);
+								Palette[i] = Color.FromArgb(ms.ReadUInt8(), Palette[i]);

 							break;
 						}
@@ -133,39 +134,63 @@ namespace OpenRA.FileFormats
 							{
 								using (var ds = new InflaterInputStream(ns))
 								{
-									var pxStride = isPaletted ? 1 : is24Bit ? 3 : 4;
-									var srcStride = Width * pxStride;
-									var destStride = Width * (isPaletted ? 1 : 4);
+									var pxStride = PixelStride;
+									var rowStride = Width * pxStride;

-									var prevLine = new byte[srcStride];
+									Span<byte> prevLine = new byte[rowStride];
 									for (var y = 0; y < Height; y++)
 									{
-										var filter = (PngFilter)ds.ReadByte();
-										var line = ds.ReadBytes(srcStride);
+										var filter = (PngFilter)ds.ReadUInt8();
+										ds.ReadBytes(Data, y * rowStride, rowStride);
+										var line = Data.AsSpan(y * rowStride, rowStride);

-										for (var i = 0; i < srcStride; i++)
-											line[i] = i < pxStride
-												? UnapplyFilter(filter, line[i], 0, prevLine[i], 0)
-												: UnapplyFilter(filter, line[i], line[i - pxStride], prevLine[i], prevLine[i - pxStride]);
-
-										if (is24Bit)
+										switch (filter)
 										{
-											// Fold alpha channel into RGB data
-											for (var i = 0; i < line.Length / 3; i++)
-											{
-												Array.Copy(line, 3 * i, Data, y * destStride + 4 * i, 3);
-												Data[y * destStride + 4 * i + 3] = 255;
-											}
+											case PngFilter.None:
+												break;
+											case PngFilter.Sub:
+												for (var i = pxStride; i < rowStride; i++)
+													line[i] += line[i - pxStride];
+												break;
+											case PngFilter.Up:
+												for (var i = 0; i < rowStride; i++)
+													line[i] += prevLine[i];
+												break;
+											case PngFilter.Average:
+												for (var i = 0; i < pxStride; i++)
+													line[i] += Average(0, prevLine[i]);
+												for (var i = pxStride; i < rowStride; i++)
+													line[i] += Average(line[i - pxStride], prevLine[i]);
+												break;
+											case PngFilter.Paeth:
+												for (var i = 0; i < pxStride; i++)
+													line[i] += Paeth(0, prevLine[i], 0);
+												for (var i = pxStride; i < rowStride; i++)
+													line[i] += Paeth(line[i - pxStride], prevLine[i], prevLine[i - pxStride]);
+												break;
+											default:
+												throw new InvalidOperationException("Unsupported Filter");
 										}
-										else
-											Array.Copy(line, 0, Data, y * destStride, line.Length);

 										prevLine = line;
 									}
+
+									static byte Average(byte a, byte b) => (byte)((a + b) / 2);
+
+									static byte Paeth(byte a, byte b, byte c)
+									{
+										var p = a + b - c;
+										var pa = Math.Abs(p - a);
+										var pb = Math.Abs(p - b);
+										var pc = Math.Abs(p - c);
+
+										return (pa <= pb && pa <= pc) ? a :
+											(pb <= pc) ? b : c;
+									}
 								}
 							}

-							if (isPaletted && Palette == null)
+							if (Type == SpriteFrameType.Indexed8 && Palette == null)
 								throw new InvalidDataException("Non-Palette indexed PNG are not supported.");

 							return;
@@ -175,7 +200,7 @@ namespace OpenRA.FileFormats
 			}
 		}

-		public Png(byte[] data, int width, int height, Color[] palette = null,
+		public Png(byte[] data, SpriteFrameType type, int width, int height, Color[] palette = null,
 			Dictionary<string, string> embeddedData = null)
 		{
 			var expectLength = width * height;
@@ -185,11 +210,46 @@ namespace OpenRA.FileFormats
 			if (data.Length != expectLength)
 				throw new InvalidDataException("Input data does not match expected length");

+			Type = type;
 			Width = width;
 			Height = height;

-			Palette = palette;
-			Data = data;
+			switch (type)
+			{
+				case SpriteFrameType.Indexed8:
+				case SpriteFrameType.Rgba32:
+				case SpriteFrameType.Rgb24:
+				{
+					// Data is already in a compatible format
+					Data = data;
+					if (type == SpriteFrameType.Indexed8)
+						Palette = palette;
+
+					break;
+				}
+
+				case SpriteFrameType.Bgra32:
+				case SpriteFrameType.Bgr24:
+				{
+					// Convert to big endian
+					Data = new byte[data.Length];
+					var stride = PixelStride;
+					for (var i = 0; i < width * height; i++)
+					{
+						Data[stride * i] = data[stride * i + 2];
+						Data[stride * i + 1] = data[stride * i + 1];
+						Data[stride * i + 2] = data[stride * i + 0];
+
+						if (type == SpriteFrameType.Bgra32)
+							Data[stride * i + 3] = data[stride * i + 3];
+					}
+
+					break;
+				}
+
+				default:
+					throw new InvalidDataException($"Unhandled SpriteFrameType {type}");
+			}

 			if (embeddedData != null)
 				EmbeddedData = embeddedData;
@@ -203,34 +263,9 @@ namespace OpenRA.FileFormats
 			return isPng;
 		}

-		static byte UnapplyFilter(PngFilter f, byte x, byte a, byte b, byte c)
-		{
-			switch (f)
-			{
-				case PngFilter.None: return x;
-				case PngFilter.Sub: return (byte)(x + a);
-				case PngFilter.Up: return (byte)(x + b);
-				case PngFilter.Average: return (byte)(x + (a + b) / 2);
-				case PngFilter.Paeth: return (byte)(x + Paeth(a, b, c));
-				default:
-					throw new InvalidOperationException("Unsupported Filter");
-			}
-		}
-
-		static byte Paeth(byte a, byte b, byte c)
-		{
-			var p = a + b - c;
-			var pa = Math.Abs(p - a);
-			var pb = Math.Abs(p - b);
-			var pc = Math.Abs(p - c);
-
-			return (pa <= pb && pa <= pc) ? a :
-				(pb <= pc) ? b : c;
-		}
-
 		[Flags]
-		enum PngColorType { Indexed = 1, Color = 2, Alpha = 4 }
-		enum PngFilter { None, Sub, Up, Average, Paeth }
+		enum PngColorType : byte { Indexed = 1, Color = 2, Alpha = 4 }
+		enum PngFilter : byte { None, Sub, Up, Average, Paeth }

 		static bool IsPaletted(byte bitDepth, PngColorType colorType)
 		{
@@ -246,7 +281,7 @@ namespace OpenRA.FileFormats
 			throw new InvalidDataException("Unknown pixel format");
 		}

-		void WritePngChunk(Stream output, string type, Stream input)
+		static void WritePngChunk(Stream output, string type, Stream input)
 		{
 			input.Position = 0;

@@ -274,9 +309,8 @@ namespace OpenRA.FileFormats
 					header.Write(IPAddress.HostToNetworkOrder(Height));
 					header.WriteByte(8); // Bit depth

-					var colorType = Palette != null
-						? PngColorType.Indexed | PngColorType.Color
-						: PngColorType.Color | PngColorType.Alpha;
+					var colorType = Type == SpriteFrameType.Indexed8 ? PngColorType.Indexed | PngColorType.Color :
+						Type == SpriteFrameType.Rgb24 ? PngColorType.Color : PngColorType.Color | PngColorType.Alpha;
 					header.WriteByte((byte)colorType);

 					header.WriteByte(0); // Compression
@@ -286,7 +320,7 @@ namespace OpenRA.FileFormats
 					WritePngChunk(output, "IHDR", header);
 				}

-				bool alphaPalette = false;
+				var alphaPalette = false;
 				if (Palette != null)
 				{
 					using (var palette = new MemoryStream())
@@ -318,12 +352,12 @@ namespace OpenRA.FileFormats
 				{
 					using (var compressed = new DeflaterOutputStream(data))
 					{
-						var stride = Width * (Palette != null ? 1 : 4);
+						var rowStride = Width * PixelStride;
 						for (var y = 0; y < Height; y++)
 						{
 							// Write uncompressed scanlines for simplicity
 							compressed.WriteByte(0);
-							compressed.Write(Data, y * stride, stride);
+							compressed.Write(Data, y * rowStride, rowStride);
 						}

 						compressed.Flush();
--- a/OpenRA.Game/FileFormats/ReplayMetadata.cs
+++ b/OpenRA.Game/FileFormats/ReplayMetadata.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -28,7 +28,7 @@ namespace OpenRA.FileFormats
 		public ReplayMetadata(GameInformation info)
 		{
 			if (info == null)
-				throw new ArgumentNullException("info");
+				throw new ArgumentNullException(nameof(info));

 			GameInfo = info;
 		}
@@ -44,7 +44,7 @@ namespace OpenRA.FileFormats
 			// Read version
 			var version = fs.ReadInt32();
 			if (version != MetaVersion)
-				throw new NotSupportedException("Metadata version {0} is not supported".F(version));
+				throw new NotSupportedException($"Metadata version {version} is not supported");

 			// Read game info (max 100K limit as a safeguard against corrupted files)
 			var data = fs.ReadString(Encoding.UTF8, 1024 * 100);
--- a/OpenRA.Game/FileSystem/FileSystem.cs
+++ b/OpenRA.Game/FileSystem/FileSystem.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -28,17 +28,17 @@ namespace OpenRA.FileSystem

 	public class FileSystem : IReadOnlyFileSystem
 	{
-		public IEnumerable<IReadOnlyPackage> MountedPackages { get { return mountedPackages.Keys; } }
-		readonly Dictionary<IReadOnlyPackage, int> mountedPackages = new Dictionary<IReadOnlyPackage, int>();
-		readonly Dictionary<string, IReadOnlyPackage> explicitMounts = new Dictionary<string, IReadOnlyPackage>();
+		public IEnumerable<IReadOnlyPackage> MountedPackages => mountedPackages.Keys;
+		readonly Dictionary<IReadOnlyPackage, int> mountedPackages = new();
+		readonly Dictionary<string, IReadOnlyPackage> explicitMounts = new();
 		readonly string modID;

 		// Mod packages that should not be disposed
-		readonly List<IReadOnlyPackage> modPackages = new List<IReadOnlyPackage>();
+		readonly List<IReadOnlyPackage> modPackages = new();
 		readonly IReadOnlyDictionary<string, Manifest> installedMods;
 		readonly IPackageLoader[] packageLoaders;

-		Cache<string, List<IReadOnlyPackage>> fileIndex = new Cache<string, List<IReadOnlyPackage>>(_ => new List<IReadOnlyPackage>());
+		Cache<string, List<IReadOnlyPackage>> fileIndex = new(_ => new List<IReadOnlyPackage>());

 		public FileSystem(string modID, IReadOnlyDictionary<string, Manifest> installedMods, IPackageLoader[] packageLoaders)
 		{
@@ -63,7 +63,7 @@ namespace OpenRA.FileSystem
 		{
 			// Raw directories are the easiest and one of the most common cases, so try these first
 			var resolvedPath = Platform.ResolvePath(filename);
-			if (!resolvedPath.Contains("|") && Directory.Exists(resolvedPath))
+			if (!resolvedPath.Contains('|') && Directory.Exists(resolvedPath))
 				return new Folder(resolvedPath);

 			// Children of another package require special handling
@@ -85,17 +85,17 @@ namespace OpenRA.FileSystem
 		{
 			var optional = name.StartsWith("~", StringComparison.Ordinal);
 			if (optional)
-				name = name.Substring(1);
+				name = name[1..];

 			try
 			{
 				IReadOnlyPackage package;
 				if (name.StartsWith("$", StringComparison.Ordinal))
 				{
-					name = name.Substring(1);
+					name = name[1..];

 					if (!installedMods.TryGetValue(name, out var mod))
-						throw new InvalidOperationException("Could not load mod '{0}'. Available mods: {1}".F(name, installedMods.Keys.JoinWith(", ")));
+						throw new InvalidOperationException($"Could not load mod '{name}'. Available mods: {installedMods.Keys.JoinWith(", ")}");

 					package = mod.Package;
 					modPackages.Add(package);
@@ -104,7 +104,7 @@ namespace OpenRA.FileSystem
 				{
 					package = OpenPackage(name);
 					if (package == null)
-						throw new InvalidOperationException("Could not open package '{0}', file not found or its format is not supported.".F(name));
+						throw new InvalidOperationException($"Could not open package '{name}', file not found or its format is not supported.");
 				}

 				Mount(package, explicitName);
@@ -203,7 +203,7 @@ namespace OpenRA.FileSystem
 		public Stream Open(string filename)
 		{
 			if (!TryOpen(filename, out var s))
-				throw new FileNotFoundException("File not found: {0}".F(filename), filename);
+				throw new FileNotFoundException($"File not found: {filename}", filename);

 			return s;
 		}
@@ -211,9 +211,9 @@ namespace OpenRA.FileSystem
 		public bool TryGetPackageContaining(string path, out IReadOnlyPackage package, out string filename)
 		{
 			var explicitSplit = path.IndexOf('|');
-			if (explicitSplit > 0 && explicitMounts.TryGetValue(path.Substring(0, explicitSplit), out package))
+			if (explicitSplit > 0 && explicitMounts.TryGetValue(path[..explicitSplit], out package))
 			{
-				filename = path.Substring(explicitSplit + 1);
+				filename = path[(explicitSplit + 1)..];
 				return true;
 			}

@@ -228,9 +228,9 @@ namespace OpenRA.FileSystem
 			var explicitSplit = filename.IndexOf('|');
 			if (explicitSplit > 0)
 			{
-				if (explicitMounts.TryGetValue(filename.Substring(0, explicitSplit), out var explicitPackage))
+				if (explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage))
 				{
-					s = explicitPackage.GetStream(filename.Substring(explicitSplit + 1));
+					s = explicitPackage.GetStream(filename[(explicitSplit + 1)..]);
 					if (s != null)
 						return true;
 				}
@@ -263,15 +263,15 @@ namespace OpenRA.FileSystem
 		{
 			var explicitSplit = filename.IndexOf('|');
 			if (explicitSplit > 0)
-				if (explicitMounts.TryGetValue(filename.Substring(0, explicitSplit), out var explicitPackage))
-					if (explicitPackage.Contains(filename.Substring(explicitSplit + 1)))
+				if (explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage))
+					if (explicitPackage.Contains(filename[(explicitSplit + 1)..]))
 						return true;

 			return fileIndex.ContainsKey(filename);
 		}

 		/// <summary>
-		/// Returns true if the given filename references an external mod via an explicit mount
+		/// Returns true if the given filename references an external mod via an explicit mount.
 		/// </summary>
 		public bool IsExternalModFile(string filename)
 		{
@@ -279,7 +279,7 @@ namespace OpenRA.FileSystem
 			if (explicitSplit < 0)
 				return false;

-			if (!explicitMounts.TryGetValue(filename.Substring(0, explicitSplit), out var explicitPackage))
+			if (!explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage))
 				return false;

 			if (installedMods[modID].Package == explicitPackage)
@@ -297,8 +297,8 @@ namespace OpenRA.FileSystem
 			var explicitSplit = path.IndexOf('|');
 			if (explicitSplit > 0 && !path.StartsWith("^"))
 			{
-				var parent = path.Substring(0, explicitSplit);
-				var filename = path.Substring(explicitSplit + 1);
+				var parent = path[..explicitSplit];
+				var filename = path[(explicitSplit + 1)..];

 				var parentPath = manifest.Packages.FirstOrDefault(kv => kv.Value == parent).Key;
 				if (parentPath == null)
@@ -306,10 +306,10 @@ namespace OpenRA.FileSystem

 				if (parentPath.StartsWith("$", StringComparison.Ordinal))
 				{
-					if (!installedMods.TryGetValue(parentPath.Substring(1), out var mod))
+					if (!installedMods.TryGetValue(parentPath[1..], out var mod))
 						return null;

-					if (!(mod.Package is Folder))
+					if (mod.Package is not Folder)
 						return null;

 					path = Path.Combine(mod.Package.Name, filename);
@@ -322,6 +322,28 @@ namespace OpenRA.FileSystem
 			return File.Exists(resolvedPath) ? resolvedPath : null;
 		}

+		public static string ResolveCaseInsensitivePath(string path)
+		{
+			var resolved = Path.GetPathRoot(path);
+
+			if (resolved == null)
+				return null;
+
+			foreach (var name in path[resolved.Length..].Split(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar))
+			{
+				// Filter out paths of the form /foo/bar/./baz
+				if (name == ".")
+					continue;
+
+				resolved = Directory.GetFileSystemEntries(resolved).FirstOrDefault(e => e.Equals(Path.Combine(resolved, name), StringComparison.InvariantCultureIgnoreCase));
+
+				if (resolved == null)
+					return null;
+			}
+
+			return resolved;
+		}
+
 		public string GetPrefix(IReadOnlyPackage package)
 		{
 			return explicitMounts.ContainsValue(package) ? explicitMounts.First(f => f.Value == package).Key : null;
--- a/OpenRA.Game/FileSystem/Folder.cs
+++ b/OpenRA.Game/FileSystem/Folder.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -18,24 +18,22 @@ namespace OpenRA.FileSystem
 {
 	public sealed class Folder : IReadWritePackage
 	{
-		readonly string path;
+		public string Name { get; }

 		public Folder(string path)
 		{
-			this.path = path;
+			Name = path;
 			if (!Directory.Exists(path))
 				Directory.CreateDirectory(path);
 		}

-		public string Name { get { return path; } }
-
 		public IEnumerable<string> Contents
 		{
 			get
 			{
 				// Order may vary on different file systems and it matters for hashing.
-				return Directory.GetFiles(path, "*", SearchOption.TopDirectoryOnly)
-					.Concat(Directory.GetDirectories(path))
+				return Directory.GetFiles(Name, "*", SearchOption.TopDirectoryOnly)
+					.Concat(Directory.GetDirectories(Name))
 					.Select(Path.GetFileName)
 					.OrderBy(f => f);
 			}
@@ -43,14 +41,14 @@ namespace OpenRA.FileSystem

 		public Stream GetStream(string filename)
 		{
-			try { return File.OpenRead(Path.Combine(path, filename)); }
+			try { return File.OpenRead(Path.Combine(Name, filename)); }
 			catch { return null; }
 		}

 		public bool Contains(string filename)
 		{
-			var combined = Path.Combine(path, filename);
-			return combined.StartsWith(path, StringComparison.Ordinal) && File.Exists(combined);
+			var combined = Path.Combine(Name, filename);
+			return combined.StartsWith(Name, StringComparison.Ordinal) && File.Exists(combined);
 		}

 		public IReadOnlyPackage OpenPackage(string filename, FileSystem context)
@@ -82,7 +80,7 @@ namespace OpenRA.FileSystem
 			// in FileSystem.OpenPackage.  Their internal name therefore contains the
 			// full parent path too.  We need to be careful to not add a second path
 			// prefix to these hacked packages.
-			var filePath = filename.StartsWith(path) ? filename : Path.Combine(path, filename);
+			var filePath = filename.StartsWith(Name) ? filename : Path.Combine(Name, filename);

 			Directory.CreateDirectory(Path.GetDirectoryName(filePath));
 			using (var s = File.Create(filePath))
@@ -96,7 +94,7 @@ namespace OpenRA.FileSystem
 			// in FileSystem.OpenPackage.  Their internal name therefore contains the
 			// full parent path too.  We need to be careful to not add a second path
 			// prefix to these hacked packages.
-			var filePath = filename.StartsWith(path) ? filename : Path.Combine(path, filename);
+			var filePath = filename.StartsWith(Name) ? filename : Path.Combine(Name, filename);
 			if (Directory.Exists(filePath))
 				Directory.Delete(filePath, true);
 			else if (File.Exists(filePath))
--- a/OpenRA.Game/FileSystem/IPackage.cs
+++ b/OpenRA.Game/FileSystem/IPackage.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
--- a/OpenRA.Game/FileSystem/ZipFile.cs
+++ b/OpenRA.Game/FileSystem/ZipFile.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -19,7 +19,7 @@ namespace OpenRA.FileSystem
 {
 	public class ZipFileLoader : IPackageLoader
 	{
-		static readonly string[] Extensions = { ".zip", ".oramap" };
+		const uint ZipSignature = 0x04034b50;

 		class ReadOnlyZipFile : IReadOnlyPackage
 		{
@@ -55,7 +55,8 @@ namespace OpenRA.FileSystem
 				get
 				{
 					foreach (ZipEntry entry in pkg)
-						yield return entry.Name;
+						if (entry.IsFile)
+							yield return entry.Name;
 				}
 			}

@@ -94,7 +95,7 @@ namespace OpenRA.FileSystem

 		sealed class ReadWriteZipFile : ReadOnlyZipFile, IReadWritePackage
 		{
-			readonly MemoryStream pkgStream = new MemoryStream();
+			readonly MemoryStream pkgStream = new();

 			public ReadWriteZipFile(string filename, bool create = false)
 			{
@@ -141,23 +142,22 @@ namespace OpenRA.FileSystem

 		sealed class ZipFolder : IReadOnlyPackage
 		{
-			public string Name { get { return path; } }
-			public ReadOnlyZipFile Parent { get; private set; }
-			readonly string path;
+			public string Name { get; }
+			public ReadOnlyZipFile Parent { get; }

 			public ZipFolder(ReadOnlyZipFile parent, string path)
 			{
 				if (path.EndsWith("/", StringComparison.Ordinal))
-					path = path.Substring(0, path.Length - 1);
+					path = path[..^1];

+				Name = path;
 				Parent = parent;
-				this.path = path;
 			}

 			public Stream GetStream(string filename)
 			{
 				// Zip files use '/' as a path separator
-				return Parent.GetStream(path + '/' + filename);
+				return Parent.GetStream(Name + '/' + filename);
 			}

 			public IEnumerable<string> Contents
@@ -166,9 +166,9 @@ namespace OpenRA.FileSystem
 				{
 					foreach (var entry in Parent.Contents)
 					{
-						if (entry.StartsWith(path, StringComparison.Ordinal) && entry != path)
+						if (entry.StartsWith(Name, StringComparison.Ordinal) && entry != Name)
 						{
-							var filename = entry.Substring(path.Length + 1);
+							var filename = entry[(Name.Length + 1)..];
 							var dirLevels = filename.Split('/').Count(c => !string.IsNullOrEmpty(c));
 							if (dirLevels == 1)
 								yield return filename;
@@ -179,18 +179,18 @@ namespace OpenRA.FileSystem

 			public bool Contains(string filename)
 			{
-				return Parent.Contains(path + '/' + filename);
+				return Parent.Contains(Name + '/' + filename);
 			}

 			public IReadOnlyPackage OpenPackage(string filename, FileSystem context)
 			{
-				return Parent.OpenPackage(path + '/' + filename, context);
+				return Parent.OpenPackage(Name + '/' + filename, context);
 			}

 			public void Dispose() { /* nothing to do */ }
 		}

-		class StaticStreamDataSource : IStaticDataSource
+		sealed class StaticStreamDataSource : IStaticDataSource
 		{
 			readonly Stream s;
 			public StaticStreamDataSource(Stream s)
@@ -206,7 +206,10 @@ namespace OpenRA.FileSystem

 		public bool TryParsePackage(Stream s, string filename, FileSystem context, out IReadOnlyPackage package)
 		{
-			if (!Extensions.Any(e => filename.EndsWith(e, StringComparison.InvariantCultureIgnoreCase)))
+			var readSignature = s.ReadUInt32();
+			s.Position -= 4;
+
+			if (readSignature != ZipSignature)
 			{
 				package = null;
 				return false;
@@ -218,10 +221,13 @@ namespace OpenRA.FileSystem

 		public static bool TryParseReadWritePackage(string filename, out IReadWritePackage package)
 		{
-			if (!Extensions.Any(e => filename.EndsWith(e, StringComparison.InvariantCultureIgnoreCase)))
+			using (var s = File.OpenRead(filename))
 			{
-				package = null;
-				return false;
+				if (s.ReadUInt32() != ZipSignature)
+				{
+					package = null;
+					return false;
+				}
 			}

 			package = new ReadWriteZipFile(filename);
--- a/OpenRA.Game/Fonts.cs
+++ b/OpenRA.Game/Fonts.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -22,7 +22,7 @@ namespace OpenRA

 	public class Fonts : IGlobalModData
 	{
-		[FieldLoader.LoadUsing("LoadFonts")]
+		[FieldLoader.LoadUsing(nameof(LoadFonts))]
 		public readonly Dictionary<string, FontData> FontList;

 		static object LoadFonts(MiniYaml y)
--- a/OpenRA.Game/Game.cs
+++ b/OpenRA.Game/Game.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -16,10 +16,8 @@ using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Net;
-using System.Reflection;
 using System.Runtime;
 using System.Threading;
-using System.Threading.Tasks;
 using OpenRA.Graphics;
 using OpenRA.Network;
 using OpenRA.Primitives;
@@ -31,8 +29,9 @@ namespace OpenRA
 {
 	public static class Game
 	{
-		public const int NetTickScale = 3; // 120 ms net tick for 40 ms local tick
-		public const int Timestep = 40;
+		[TranslationReference("filename")]
+		const string SavedScreenshot = "notification-saved-screenshot";
+
 		public const int TimestepJankThreshold = 250; // Don't catch up for delays larger than 250ms

 		public static InstalledMods Mods { get; private set; }
@@ -42,13 +41,14 @@ namespace OpenRA
 		public static Settings Settings;
 		public static CursorManager Cursor;
 		public static bool HideCursor;
+
 		static WorldRenderer worldRenderer;
 		static string modLaunchWrapper;

 		internal static OrderManager OrderManager;
 		static Server.Server server;

-		public static MersenneTwister CosmeticRandom = new MersenneTwister(); // not synced
+		public static MersenneTwister CosmeticRandom = new(); // not synced

 		public static Renderer Renderer;
 		public static Sound Sound;
@@ -56,7 +56,6 @@ namespace OpenRA
 		public static string EngineVersion { get; private set; }
 		public static LocalPlayerProfile LocalPlayerProfile;

-		static Task discoverNat;
 		static bool takeScreenshot = false;
 		static Benchmark benchmark = null;

@@ -64,12 +63,18 @@ namespace OpenRA

 		public static OrderManager JoinServer(ConnectionTarget endpoint, string password, bool recordReplay = true)
 		{
-			var connection = new NetworkConnection(endpoint);
+			var newConnection = new NetworkConnection(endpoint);
 			if (recordReplay)
-				connection.StartRecording(() => { return TimestampedFilename(); });
+				newConnection.StartRecording(() => TimestampedFilename());

-			var om = new OrderManager(endpoint, password, connection);
+			var om = new OrderManager(newConnection);
 			JoinInner(om);
+			CurrentServerSettings.Password = password;
+			CurrentServerSettings.Target = endpoint;
+
+			lastConnectionState = ConnectionState.PreConnecting;
+			ConnectionStateChanged(OrderManager, password, newConnection);
+
 			return om;
 		}

@@ -81,34 +86,56 @@ namespace OpenRA

 		static void JoinInner(OrderManager om)
 		{
-			OrderManager?.Dispose();
+			// Refresh TextNotificationsManager before the game starts.
+			TextNotificationsManager.Clear();
+
+			// HACK: The shellmap World and OrderManager are owned by the main menu's WorldRenderer instead of Game.
+			// This allows us to switch Game.OrderManager from the shellmap to the new network connection when joining
+			// a lobby, while keeping the OrderManager that runs the shellmap intact.
+			// A matching check in World.Dispose (which is called by WorldRenderer.Dispose) makes sure that we dispose
+			// the shellmap's OM when a lobby game actually starts.
+			if (OrderManager?.World == null || OrderManager.World.Type != WorldType.Shellmap)
+				OrderManager?.Dispose();
+
 			OrderManager = om;
-			lastConnectionState = ConnectionState.PreConnecting;
-			ConnectionStateChanged(OrderManager);
 		}

 		public static void JoinReplay(string replayFile)
 		{
-			JoinInner(new OrderManager(new ConnectionTarget(), "", new ReplayConnection(replayFile)));
+			JoinInner(new OrderManager(new ReplayConnection(replayFile)));
 		}

 		static void JoinLocal()
 		{
-			JoinInner(new OrderManager(new ConnectionTarget(), "", new EchoConnection()));
+			JoinInner(new OrderManager(new EchoConnection()));
+
+			// Add a spectator client for the local player
+			// On the shellmap this player is controlling the map via scripted orders
+			OrderManager.LobbyInfo.Clients.Add(new Session.Client
+			{
+				Index = OrderManager.Connection.LocalClientId,
+				Name = Settings.Player.Name,
+				PreferredColor = Settings.Player.Color,
+				Color = Settings.Player.Color,
+				Faction = "Random",
+				SpawnPoint = 0,
+				Team = 0,
+				State = Session.ClientState.Ready
+			});
 		}

 		// More accurate replacement for Environment.TickCount
-		static Stopwatch stopwatch = Stopwatch.StartNew();
-		public static long RunTime { get { return stopwatch.ElapsedMilliseconds; } }
+		static readonly Stopwatch Stopwatch = Stopwatch.StartNew();
+		public static long RunTime => Stopwatch.ElapsedMilliseconds;

 		public static int RenderFrame = 0;
-		public static int NetFrameNumber { get { return OrderManager.NetFrameNumber; } }
-		public static int LocalTick { get { return OrderManager.LocalFrameNumber; } }
+		public static int NetFrameNumber => OrderManager.NetFrameNumber;
+		public static int LocalTick => OrderManager.LocalFrameNumber;

 		public static event Action<ConnectionTarget> OnRemoteDirectConnect = _ => { };
-		public static event Action<OrderManager> ConnectionStateChanged = _ => { };
+		public static event Action<OrderManager, string, NetworkConnection> ConnectionStateChanged = (om, pass, conn) => { };
 		static ConnectionState lastConnectionState = ConnectionState.PreConnecting;
-		public static int LocalClientId { get { return OrderManager.Connection.LocalClientId; } }
+		public static int LocalClientId => OrderManager.Connection.LocalClientId;

 		public static void RemoteDirectConnect(ConnectionTarget endpoint)
 		{
@@ -160,12 +187,8 @@ namespace OpenRA
 			Cursor.SetCursor(null);
 			BeforeGameStart();

-			Map map;
-
-			using (new PerfTimer("PrepareMap"))
-				map = ModData.PrepareMap(mapUID);
 			using (new PerfTimer("NewWorld"))
-				OrderManager.World = new World(ModData, map, OrderManager, type);
+				OrderManager.World = new World(mapUID, ModData, OrderManager, type);

 			OrderManager.World.GameOver += FinishBenchmark;

@@ -186,11 +209,9 @@ namespace OpenRA
 			Ui.MouseFocusWidget = null;
 			Ui.KeyboardFocusWidget = null;

-			OrderManager.LocalFrameNumber = 0;
-			OrderManager.LastTickTime = RunTime;
 			OrderManager.StartGame();
 			worldRenderer.RefreshPalette();
-			Cursor.SetCursor("default");
+			Cursor.SetCursor(ChromeMetrics.Get<string>("DefaultCursor"));

 			// Now loading is completed, now is the ideal time to run a GC and compact the LOH.
 			// - All the temporary garbage created during loading can be collected.
@@ -206,15 +227,26 @@ namespace OpenRA
 		public static void RestartGame()
 		{
 			var replay = OrderManager.Connection as ReplayConnection;
-			var replayName = replay != null ? replay.Filename : null;
+			var replayName = replay?.Filename;
 			var lobbyInfo = OrderManager.LobbyInfo;

 			// Reseed the RNG so this isn't an exact repeat of the last game
 			lobbyInfo.GlobalSettings.RandomSeed = CosmeticRandom.Next();

+			// Note: the map may have been changed on disk outside the game, changing its UID.
+			// Use the updated UID if we have tracked the update instead of failing.
+			lobbyInfo.GlobalSettings.Map = ModData.MapCache.GetUpdatedMap(lobbyInfo.GlobalSettings.Map);
+			if (lobbyInfo.GlobalSettings.Map == null)
+			{
+				Disconnect();
+				Ui.ResetAll();
+				LoadShellMap();
+				return;
+			}
+
 			var orders = new[]
 			{
-					Order.Command("sync_lobby {0}".F(lobbyInfo.Serialize())),
+					Order.Command($"sync_lobby {lobbyInfo.Serialize()}"),
 					Order.Command("startgame")
 			};

@@ -233,15 +265,14 @@ namespace OpenRA
 		{
 			OrderManager om = null;

-			Action lobbyReady = null;
-			lobbyReady = () =>
+			void LobbyReady()
 			{
-				LobbyInfoChanged -= lobbyReady;
+				LobbyInfoChanged -= LobbyReady;
 				foreach (var o in setupOrders)
 					om.IssueOrder(o);
-			};
+			}

-			LobbyInfoChanged += lobbyReady;
+			LobbyInfoChanged += LobbyReady;

 			om = JoinServer(CreateLocalServer(mapUID), "");
 		}
@@ -284,7 +315,7 @@ namespace OpenRA
 			if (!string.IsNullOrEmpty(supportDirArg))
 				Platform.OverrideSupportDir(supportDirArg);

-			Console.WriteLine("Platform is {0}", Platform.CurrentPlatform);
+			Console.WriteLine($"Platform is {Platform.CurrentPlatform} ({Platform.CurrentArchitecture})");

 			// Load the engine version as early as possible so it can be written to exception logs
 			try
@@ -296,12 +327,13 @@ namespace OpenRA
 			if (string.IsNullOrEmpty(EngineVersion))
 				EngineVersion = "Unknown";

-			Console.WriteLine("Engine version is {0}", EngineVersion);
+			Console.WriteLine($"Engine version is {EngineVersion}");
+			Console.WriteLine($"Runtime: {Platform.RuntimeVersion}");

 			// Special case handling of Game.Mod argument: if it matches a real filesystem path
 			// then we use this to override the mod search path, and replace it with the mod id
 			var modID = args.GetValue("Game.Mod", null);
-			var explicitModPaths = new string[0];
+			var explicitModPaths = Array.Empty<string>();
 			if (modID != null && (File.Exists(modID) || Directory.Exists(modID)))
 			{
 				explicitModPaths = new[] { modID };
@@ -329,9 +361,17 @@ namespace OpenRA
 				try
 				{
 					var rendererPath = Path.Combine(Platform.BinDir, "OpenRA.Platforms." + p + ".dll");
-					var assembly = Assembly.LoadFile(rendererPath);

+#if NET5_0_OR_GREATER
+					var loader = new AssemblyLoader(rendererPath);
+					var platformType = loader.LoadDefaultAssembly().GetTypes().SingleOrDefault(t => typeof(IPlatform).IsAssignableFrom(t));
+
+#else
+					// NOTE: This is currently the only use of System.Reflection in this file, so would give an unused using error if we import it above
+					var assembly = System.Reflection.Assembly.LoadFile(rendererPath);
 					var platformType = assembly.GetTypes().SingleOrDefault(t => typeof(IPlatform).IsAssignableFrom(t));
+#endif
+
 					if (platformType == null)
 						throw new InvalidOperationException("Platform dll must include exactly one IPlatform implementation.");

@@ -343,7 +383,7 @@ namespace OpenRA
 				}
 				catch (Exception e)
 				{
-					Log.Write("graphics", "{0}", e);
+					Log.Write("graphics", $"{e}");
 					Console.WriteLine("Renderer initialization failed. Check graphics.log for details.");

 					Renderer?.Dispose();
@@ -352,8 +392,7 @@ namespace OpenRA
 				}
 			}

-			if (Settings.Server.DiscoverNatDevices)
-				discoverNat = UPnP.DiscoverNatDevices(Settings.Server.NatDiscoveryTimeout);
+			Nat.Initialize();

 			var modSearchArg = args.GetValue("Engine.ModSearchPaths", null);
 			var modSearchPaths = modSearchArg != null ?
@@ -363,7 +402,7 @@ namespace OpenRA
 			Mods = new InstalledMods(modSearchPaths, explicitModPaths);
 			Console.WriteLine("Internal mods:");
 			foreach (var mod in Mods)
-				Console.WriteLine("\t{0}: {1} ({2})", mod.Key, mod.Value.Metadata.Title, mod.Value.Metadata.Version);
+				Console.WriteLine($"\t{mod.Key}: {mod.Value.Metadata.Title} ({mod.Value.Metadata.Version})");

 			modLaunchWrapper = args.GetValue("Engine.LaunchWrapper", null);

@@ -377,26 +416,18 @@ namespace OpenRA
 				// Sanitize input from platform-specific launchers
 				// Process.Start requires paths to not be quoted, even if they contain spaces
 				if (launchPath != null && launchPath.First() == '"' && launchPath.Last() == '"')
-					launchPath = launchPath.Substring(1, launchPath.Length - 2);
+					launchPath = launchPath[1..^1];

-				if (launchPath == null)
-				{
-					// When launching the assembly directly we must propagate the Engine.EngineDir argument if defined
-					// Platform-specific launchers are expected to manage this internally.
-					launchPath = Assembly.GetEntryAssembly().Location;
-					if (!string.IsNullOrEmpty(engineDirArg))
-						launchArgs.Add("Engine.EngineDir=\"" + engineDirArg + "\"");
-				}
+				// Metadata registration requires an explicit launch path
+				if (launchPath != null)
+					ExternalMods.Register(Mods[modID], launchPath, launchArgs, ModRegistration.User);

-				ExternalMods.Register(Mods[modID], launchPath, launchArgs, ModRegistration.User);
-
-				if (ExternalMods.TryGetValue(ExternalMod.MakeKey(Mods[modID]), out var activeMod))
-					ExternalMods.ClearInvalidRegistrations(activeMod, ModRegistration.User);
+				ExternalMods.ClearInvalidRegistrations(ModRegistration.User);
 			}

 			Console.WriteLine("External mods:");
 			foreach (var mod in ExternalMods)
-				Console.WriteLine("\t{0}: {1} ({2})", mod.Key, mod.Value.Title, mod.Value.Version);
+				Console.WriteLine($"\t{mod.Key}: {mod.Value.Title} ({mod.Value.Version})");

 			InitializeMod(modID, args);
 		}
@@ -405,7 +436,7 @@ namespace OpenRA
 		{
 			// Clear static state if we have switched mods
 			LobbyInfoChanged = () => { };
-			ConnectionStateChanged = om => { };
+			ConnectionStateChanged = (om, p, conn) => { };
 			BeforeGameStart = () => { };
 			OnRemoteDirectConnect = endpoint => { };
 			delayedActions = new ActionQueue();
@@ -429,9 +460,9 @@ namespace OpenRA
 				throw new InvalidOperationException("Game.Mod argument missing.");

 			if (!Mods.ContainsKey(mod))
-				throw new InvalidOperationException("Unknown or invalid mod '{0}'.".F(mod));
+				throw new InvalidOperationException($"Unknown or invalid mod '{mod}'.");

-			Console.WriteLine("Loading mod: {0}", mod);
+			Console.WriteLine($"Loading mod: {mod}");

 			Sound.StopVideo();

@@ -442,19 +473,22 @@ namespace OpenRA
 			if (!ModData.LoadScreen.BeforeLoad())
 				return;

-			using (new PerfTimer("LoadMaps"))
-				ModData.MapCache.LoadMaps();
-
 			ModData.InitializeLoaders(ModData.DefaultFileSystem);
 			Renderer.InitializeFonts(ModData);

+			using (new PerfTimer("LoadMaps"))
+				ModData.MapCache.LoadMaps();
+
 			var grid = ModData.Manifest.Contains<MapGrid>() ? ModData.Manifest.Get<MapGrid>() : null;
 			Renderer.InitializeDepthBuffer(grid);

 			Cursor?.Dispose();
-
 			Cursor = new CursorManager(ModData.CursorProvider);

+			var metadata = ModData.Manifest.Metadata;
+			if (!string.IsNullOrEmpty(metadata.WindowTitle))
+				Renderer.Window.SetWindowTitle(metadata.WindowTitle);
+
 			PerfHistory.Items["render"].HasNormalTick = false;
 			PerfHistory.Items["batches"].HasNormalTick = false;
 			PerfHistory.Items["render_world"].HasNormalTick = false;
@@ -464,31 +498,18 @@ namespace OpenRA

 			JoinLocal();

-			try
-			{
-				discoverNat?.Wait();
-			}
-			catch (Exception e)
-			{
-				Console.WriteLine("NAT discovery failed: {0}", e.Message);
-				Log.Write("nat", e.ToString());
-			}
-
-			ChromeMetrics.TryGet("ChatMessageColor", out chatMessageColor);
-			ChromeMetrics.TryGet("SystemMessageColor", out systemMessageColor);
-
 			ModData.LoadScreen.StartGame(args);
 		}

 		public static void LoadEditor(string mapUid)
 		{
+			JoinLocal();
 			StartGame(mapUid, WorldType.Editor);
 		}

 		public static void LoadShellMap()
 		{
 			var shellmap = ChooseShellmap();
-
 			using (new PerfTimer("StartGame"))
 			{
 				StartGame(shellmap, WorldType.Shellmap);
@@ -542,9 +563,8 @@ namespace OpenRA

 		// Note: These delayed actions should only be used by widgets or disposing objects
 		// - things that depend on a particular world should be queuing them on the world actor.
-		static volatile ActionQueue delayedActions = new ActionQueue();
-		static Color systemMessageColor = Color.White;
-		static Color chatMessageColor = Color.White;
+		static volatile ActionQueue delayedActions = new();
+
 		public static void RunAfterTick(Action a) { delayedActions.Add(a, RunTime); }
 		public static void RunAfterDelay(int delayMilliseconds, Action a) { delayedActions.Add(a, RunTime + delayMilliseconds); }

@@ -561,7 +581,7 @@ namespace OpenRA
 				Log.Write("debug", "Taking screenshot " + path);

 				Renderer.SaveScreenshot(path);
-				Debug("Saved screenshot " + filename);
+				TextNotificationsManager.Debug(TranslationProvider.GetString(SavedScreenshot, Translation.Arguments("filename", filename)));
 			}
 		}

@@ -571,62 +591,38 @@ namespace OpenRA

 			var world = orderManager.World;

-			var uiTickDelta = tick - Ui.LastTickTime;
-			if (uiTickDelta >= Timestep)
+			if (Ui.LastTickTime.ShouldAdvance(tick))
 			{
-				// Explained below for the world tick calculation
-				var integralTickTimestep = (uiTickDelta / Timestep) * Timestep;
-				Ui.LastTickTime += integralTickTimestep >= TimestepJankThreshold ? integralTickTimestep : Timestep;
-
-				Sync.RunUnsynced(Settings.Debug.SyncCheckUnsyncedCode, world, Ui.Tick);
+				Ui.LastTickTime.AdvanceTickTime(tick);
+				Sync.RunUnsynced(world, Ui.Tick);
 				Cursor.Tick();
 			}

-			var worldTimestep = world == null ? Timestep : world.IsLoadingGameSave ? 1 : world.Timestep;
-			var worldTickDelta = tick - orderManager.LastTickTime;
-			if (worldTimestep != 0 && worldTickDelta >= worldTimestep)
+			if (orderManager.LastTickTime.ShouldAdvance(tick))
 			{
 				using (new PerfSample("tick_time"))
 				{
-					// Tick the world to advance the world time to match real time:
-					//    If dt < TickJankThreshold then we should try and catch up by repeatedly ticking
-					//    If dt >= TickJankThreshold then we should accept the jank and progress at the normal rate
-					// dt is rounded down to an integer tick count in order to preserve fractional tick components.
-					var integralTickTimestep = (worldTickDelta / worldTimestep) * worldTimestep;
-					orderManager.LastTickTime += integralTickTimestep >= TimestepJankThreshold ? integralTickTimestep : worldTimestep;
+					orderManager.LastTickTime.AdvanceTickTime(tick);

 					Sound.Tick();
-					Sync.RunUnsynced(Settings.Debug.SyncCheckUnsyncedCode, world, orderManager.TickImmediate);
+
+					Sync.RunUnsynced(world, orderManager.TickImmediate);

 					if (world == null)
 						return;

-					var isNetTick = LocalTick % NetTickScale == 0;
-
-					if (!isNetTick || orderManager.IsReadyForNextFrame)
+					if (orderManager.TryTick())
 					{
-						++orderManager.LocalFrameNumber;
-
-						Log.Write("debug", "--Tick: {0} ({1})", LocalTick, isNetTick ? "net" : "local");
-
-						if (isNetTick)
-							orderManager.Tick();
-
-						Sync.RunUnsynced(Settings.Debug.SyncCheckUnsyncedCode, world, () =>
-						{
-							world.OrderGenerator.Tick(world);
-						});
+						Sync.RunUnsynced(world, () => world.OrderGenerator.Tick(world));

 						world.Tick();

 						PerfHistory.Tick();
 					}
-					else if (orderManager.NetFrameNumber == 0)
-						orderManager.LastTickTime = RunTime;

 					// Wait until we have done our first world Tick before TickRendering
 					if (orderManager.LocalFrameNumber > 0)
-						Sync.RunUnsynced(Settings.Debug.SyncCheckUnsyncedCode, world, () => world.TickRender(worldRenderer));
+						Sync.RunUnsynced(world, () => world.TickRender(worldRenderer));
 				}

 				benchmark?.Tick(LocalTick);
@@ -637,10 +633,10 @@ namespace OpenRA
 		{
 			PerformDelayedActions();

-			if (OrderManager.Connection.ConnectionState != lastConnectionState)
+			if (OrderManager.Connection is NetworkConnection nc && nc.ConnectionState != lastConnectionState)
 			{
-				lastConnectionState = OrderManager.Connection.ConnectionState;
-				ConnectionStateChanged(OrderManager);
+				lastConnectionState = nc.ConnectionState;
+				ConnectionStateChanged(OrderManager, null, nc);
 			}

 			InnerLogicTick(OrderManager);
@@ -777,13 +773,20 @@ namespace OpenRA

 			while (state == RunStatus.Running)
 			{
-				// Ideal time between logic updates. Timestep = 0 means the game is paused
-				// but we still call LogicTick() because it handles pausing internally.
-				var logicInterval = worldRenderer != null && worldRenderer.World.Timestep != 0 ? worldRenderer.World.Timestep : Timestep;
+				var logicInterval = Ui.Timestep;
+				var logicWorld = worldRenderer?.World;
+
+				// ReplayTimestep = 0 means the replay is paused: we need to keep logicInterval as UI.Timestep to avoid breakage
+				if (logicWorld != null && !(logicWorld.IsReplay && logicWorld.ReplayTimestep == 0))
+					logicInterval = logicWorld == OrderManager.World ? OrderManager.SuggestedTimestep : logicWorld.Timestep;

 				// Ideal time between screen updates
-				var maxFramerate = Settings.Graphics.CapFramerate ? Settings.Graphics.MaxFramerate.Clamp(1, 1000) : 1000;
-				var renderInterval = 1000 / maxFramerate;
+				var renderInterval = logicInterval;
+				if (!Settings.Graphics.CapFramerateToGameFps)
+				{
+					var maxFramerate = Settings.Graphics.CapFramerate ? Settings.Graphics.MaxFramerate.Clamp(1, 1000) : 1000;
+					renderInterval = 1000 / maxFramerate;
+				}

 				// Tick as fast as possible while restoring game saves, capping rendering at 5 FPS
 				if (OrderManager.World != null && OrderManager.World.IsLoadingGameSave)
@@ -817,8 +820,7 @@ namespace OpenRA

 					var haveSomeTimeUntilNextLogic = now < nextLogic;
 					var isTimeToRender = now >= nextRender;
-
-					if ((isTimeToRender && haveSomeTimeUntilNextLogic) || forceRender)
+					if (!Renderer.WindowIsSuspended && ((isTimeToRender && haveSomeTimeUntilNextLogic) || forceRender))
 					{
 						nextRender = now + renderInterval;

@@ -833,6 +835,19 @@ namespace OpenRA
 						RenderTick();
 						renderBeforeNextTick = false;
 					}
+
+					// Simulate a render tick if it was time to render but we skip actually rendering
+					if (Renderer.WindowIsSuspended && isTimeToRender)
+					{
+						// Make sure that nextUpdate is set to a proper minimum interval
+						nextRender = now + renderInterval;
+
+						// Still process SDL events to allow a restore to come through
+						Renderer.Window.PumpInput(new NullInputHandler());
+
+						// Ensure that we still logic tick despite not rendering
+						renderBeforeNextTick = false;
+					}
 				}
 				else
 					Thread.Sleep((int)(nextUpdate - now));
@@ -874,26 +889,6 @@ namespace OpenRA
 			state = RunStatus.Success;
 		}

-		public static void AddSystemLine(string text)
-		{
-			AddSystemLine("Battlefield Control", text);
-		}
-
-		public static void AddSystemLine(string name, string text)
-		{
-			OrderManager.AddChatLine(name, systemMessageColor, text, systemMessageColor);
-		}
-
-		public static void AddChatLine(string name, Color nameColor, string text)
-		{
-			OrderManager.AddChatLine(name, nameColor, text, chatMessageColor);
-		}
-
-		public static void Debug(string s, params object[] args)
-		{
-			AddSystemLine("Debug", string.Format(s, args));
-		}
-
 		public static void Disconnect()
 		{
 			OrderManager.World?.TraitDict.PrintReport();
@@ -965,16 +960,13 @@ namespace OpenRA
 		{
 			var orders = new List<Order>
 			{
-				Order.Command("option gamespeed {0}".F("default")),
-				Order.Command("state {0}".F(Session.ClientState.Ready))
+				Order.Command("option gamespeed default"),
+				Order.Command($"state {Session.ClientState.Ready}")
 			};

-			var path = Platform.ResolvePath(launchMap);
-			var map = ModData.MapCache.SingleOrDefault(m => m.Uid == launchMap) ??
-				ModData.MapCache.SingleOrDefault(m => m.Package.Name == path);
-
+			var map = ModData.MapCache.SingleOrDefault(m => m.Uid == launchMap || Path.GetFileName(m.Package.Name) == launchMap);
 			if (map == null)
-				throw new InvalidOperationException("Could not find map '{0}'.".F(launchMap));
+				throw new ArgumentException($"Could not find map '{launchMap}'.");

 			CreateAndStartLocalServer(map.Uid, orders);
 		}
@@ -988,4 +980,11 @@ namespace OpenRA
 			}
 		}
 	}
+
+	public static class CurrentServerSettings
+	{
+		public static string Password;
+		public static ConnectionTarget Target;
+		public static ExternalMod ServerExternalMod;
+	}
 }
--- a/OpenRA.Game/GameInformation.cs
+++ b/OpenRA.Game/GameInformation.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -33,12 +33,13 @@ namespace OpenRA
 		public DateTime EndTimeUtc;

 		/// <summary>Gets the game's duration, from the time the game started until the replay recording stopped.</summary>
-		public TimeSpan Duration { get { return EndTimeUtc > StartTimeUtc ? EndTimeUtc - StartTimeUtc : TimeSpan.Zero; } }
-		public IList<Player> Players { get; private set; }
-		public HashSet<int> DisabledSpawnPoints = new HashSet<int>();
-		public MapPreview MapPreview { get { return Game.ModData.MapCache[MapUid]; } }
+		public TimeSpan Duration => EndTimeUtc > StartTimeUtc ? EndTimeUtc - StartTimeUtc : TimeSpan.Zero;
+
+		public IList<Player> Players { get; }
+		public HashSet<int> DisabledSpawnPoints = new();
+		public MapPreview MapPreview => Game.ModData.MapCache[MapUid];
 		public IEnumerable<Player> HumanPlayers { get { return Players.Where(p => p.IsHuman); } }
-		public bool IsSinglePlayer { get { return HumanPlayers.Count() == 1; } }
+		public bool IsSinglePlayer => HumanPlayers.Count() == 1;

 		readonly Dictionary<OpenRA.Player, Player> playersByRuntime;

@@ -75,7 +76,7 @@ namespace OpenRA
 			}
 			catch (YamlException)
 			{
-				Log.Write("debug", "GameInformation deserialized invalid MiniYaml:\n{0}".F(data));
+				Log.Write("debug", $"GameInformation deserialized invalid MiniYaml:\n{data}");
 				throw;
 			}
 		}
@@ -88,7 +89,7 @@ namespace OpenRA
 			};

 			for (var i = 0; i < Players.Count; i++)
-				nodes.Add(new MiniYamlNode("Player@{0}".F(i), FieldSaver.Save(Players[i])));
+				nodes.Add(new MiniYamlNode($"Player@{i}", FieldSaver.Save(Players[i])));

 			return nodes.WriteToString();
 		}
@@ -97,10 +98,10 @@ namespace OpenRA
 		public void AddPlayer(OpenRA.Player runtimePlayer, Session lobbyInfo)
 		{
 			if (runtimePlayer == null)
-				throw new ArgumentNullException("runtimePlayer");
+				throw new ArgumentNullException(nameof(runtimePlayer));

 			if (lobbyInfo == null)
-				throw new ArgumentNullException("lobbyInfo");
+				throw new ArgumentNullException(nameof(lobbyInfo));

 			// We don't care about spectators and map players
 			if (runtimePlayer.NonCombatant || !runtimePlayer.Playable)
@@ -123,6 +124,7 @@ namespace OpenRA
 				DisplayFactionId = runtimePlayer.DisplayFaction.InternalName,
 				Color = runtimePlayer.Color,
 				Team = client.Team,
+				Handicap = client.Handicap,
 				SpawnPoint = runtimePlayer.SpawnPoint,
 				IsRandomFaction = runtimePlayer.Faction.InternalName != client.Faction,
 				IsRandomSpawnPoint = runtimePlayer.DisplaySpawnPoint == 0,
@@ -166,6 +168,7 @@ namespace OpenRA
 			/// <summary>The team ID on start-up, or 0 if the player is not part of a team.</summary>
 			public int Team;
 			public int SpawnPoint;
+			public int Handicap;

 			/// <summary>True if the faction was chosen at random; otherwise, false.</summary>
 			public bool IsRandomFaction;
--- a/OpenRA.Game/GameRules/ActorInfo.cs
+++ b/OpenRA.Game/GameRules/ActorInfo.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -32,7 +32,7 @@ namespace OpenRA
 		/// You can remove inherited traits by adding a - in front of them as in -TraitName: to inherit everything, but this trait.
 		/// </summary>
 		public readonly string Name;
-		readonly TypeDictionary traits = new TypeDictionary();
+		readonly TypeDictionary traits = new();
 		List<TraitInfo> constructOrderCache = null;

 		public ActorInfo(ObjectCreator creator, string name, MiniYaml node)
@@ -61,7 +61,7 @@ namespace OpenRA
 			}
 			catch (YamlException e)
 			{
-				throw new YamlException("Actor type {0}: {1}".F(name, e.Message));
+				throw new YamlException($"Actor type {name}: {e.Message}");
 			}
 		}

@@ -76,8 +76,7 @@ namespace OpenRA
 		static TraitInfo LoadTraitInfo(ObjectCreator creator, string traitName, MiniYaml my)
 		{
 			if (!string.IsNullOrEmpty(my.Value))
-				throw new YamlException("Junk value `{0}` on trait node {1}"
-				.F(my.Value, traitName));
+				throw new YamlException($"Junk value `{my.Value}` on trait node {traitName}");

 			// HACK: The linter does not want to crash when a trait doesn't exist but only print an error instead
 			// ObjectCreator will only return null to signal us to abort here if the linter is running
@@ -89,7 +88,7 @@ namespace OpenRA
 			try
 			{
 				if (traitInstance.Length > 1)
-					info.GetType().GetField("InstanceName").SetValue(info, traitInstance[1]);
+					info.GetType().GetField(nameof(info.InstanceName)).SetValue(info, traitInstance[1]);

 				FieldLoader.Load(info, my);
 			}
@@ -111,39 +110,51 @@ namespace OpenRA
 			{
 				Trait = i,
 				Type = i.GetType(),
-				Dependencies = PrerequisitesOf(i).ToList()
+				Dependencies = PrerequisitesOf(i).ToList(),
+				OptionalDependencies = OptionalPrerequisitesOf(i).ToList()
 			}).ToList();

-			var resolved = source.Where(s => !s.Dependencies.Any()).ToList();
-			var unresolved = source.Except(resolved);
+			var resolved = source.Where(s => s.Dependencies.Count == 0 && s.OptionalDependencies.Count == 0).ToList();
+			var unresolved = source.ToHashSet();
+			unresolved.ExceptWith(resolved);

-			var testResolve = new Func<Type, Type, bool>((a, b) => a == b || a.IsAssignableFrom(b));
+			static bool AreResolvable(Type a, Type b) => a.IsAssignableFrom(b);

 			// This query detects which unresolved traits can be immediately resolved as all their direct dependencies are met.
 			var more = unresolved.Where(u =>
 				u.Dependencies.All(d => // To be resolvable, all dependencies must be satisfied according to the following conditions:
-					resolved.Exists(r => testResolve(d, r.Type)) && // There must exist a resolved trait that meets the dependency.
-					!unresolved.Any(u1 => testResolve(d, u1.Type)))); // All matching traits that meet this dependency must be resolved first.
+					resolved.Exists(r => AreResolvable(d, r.Type)) && // There must exist a resolved trait that meets the dependency.
+					!unresolved.Any(u1 => AreResolvable(d, u1.Type))) && // All matching traits that meet this dependency must be resolved first.
+				u.OptionalDependencies.All(d => // To be resolvable, all optional dependencies must be satisfied according to the following condition:
+					!unresolved.Any(u1 => AreResolvable(d, u1.Type)))); // All matching traits that meet this optional dependencies must be resolved first.

 			// Continue resolving traits as long as possible.
 			// Each time we resolve some traits, this means dependencies for other traits may then be possible to satisfy in the next pass.
-			while (more.Any())
-				resolved.AddRange(more);
-
-			if (unresolved.Any())
+			var readyToResolve = more.ToList();
+			while (readyToResolve.Count != 0)
 			{
-				var exceptionString = "ActorInfo(\"" + Name + "\") failed to initialize because of the following:\r\n";
-				var missing = unresolved.SelectMany(u => u.Dependencies.Where(d => !source.Any(s => testResolve(d, s.Type)))).Distinct();
+				resolved.AddRange(readyToResolve);
+				unresolved.ExceptWith(readyToResolve);
+				readyToResolve.Clear();
+				readyToResolve.AddRange(more);
+			}

-				exceptionString += "Missing:\r\n";
+			if (unresolved.Count != 0)
+			{
+				var exceptionString = "ActorInfo(\"" + Name + "\") failed to initialize because of the following:\n";
+				var missing = unresolved.SelectMany(u => u.Dependencies.Where(d => !source.Any(s => AreResolvable(d, s.Type)))).Distinct();
+
+				exceptionString += "Missing:\n";
 				foreach (var m in missing)
-					exceptionString += m + " \r\n";
+					exceptionString += m + " \n";

-				exceptionString += "Unresolved:\r\n";
+				exceptionString += "Unresolved:\n";
 				foreach (var u in unresolved)
 				{
 					var deps = u.Dependencies.Where(d => !resolved.Exists(r => r.Type == d));
-					exceptionString += u.Type + ": { " + string.Join(", ", deps) + " }\r\n";
+					var optDeps = u.OptionalDependencies.Where(d => !resolved.Exists(r => r.Type == d));
+					var allDeps = string.Join(", ", deps.Select(o => o.ToString()).Concat(optDeps.Select(o => $"[{o}]")));
+					exceptionString += $"{u.Type}: {{ {allDeps} }}\n";
 				}

 				throw new YamlException(exceptionString);
@@ -162,6 +173,15 @@ namespace OpenRA
 				.Select(t => t.GetGenericArguments()[0]);
 		}

+		public static IEnumerable<Type> OptionalPrerequisitesOf(TraitInfo info)
+		{
+			return info
+				.GetType()
+				.GetInterfaces()
+				.Where(t => t.IsGenericType && t.GetGenericTypeDefinition() == typeof(NotBefore<>))
+				.Select(t => t.GetGenericArguments()[0]);
+		}
+
 		public bool HasTraitInfo<T>() where T : ITraitInfoInterface { return traits.Contains<T>(); }
 		public T TraitInfo<T>() where T : ITraitInfoInterface { return traits.Get<T>(); }
 		public T TraitInfoOrDefault<T>() where T : ITraitInfoInterface { return traits.GetOrDefault<T>(); }
--- a/OpenRA.Game/GameRules/MusicInfo.cs
+++ b/OpenRA.Game/GameRules/MusicInfo.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -9,7 +9,6 @@
 */
 #endregion

-using System.IO;
 using OpenRA.FileSystem;

 namespace OpenRA.GameRules
@@ -29,14 +28,14 @@ namespace OpenRA.GameRules
 			Title = value.Value;

 			var nd = value.ToDictionary();
-			if (nd.ContainsKey("Hidden"))
-				bool.TryParse(nd["Hidden"].Value, out Hidden);
+			if (nd.TryGetValue("Hidden", out var yaml))
+				bool.TryParse(yaml.Value, out Hidden);

-			if (nd.ContainsKey("VolumeModifier"))
-				VolumeModifier = FieldLoader.GetValue<float>("VolumeModifier", nd["VolumeModifier"].Value);
+			if (nd.TryGetValue("VolumeModifier", out yaml))
+				VolumeModifier = FieldLoader.GetValue<float>("VolumeModifier", yaml.Value);

-			var ext = nd.ContainsKey("Extension") ? nd["Extension"].Value : "aud";
-			Filename = (nd.ContainsKey("Filename") ? nd["Filename"].Value : key) + "." + ext;
+			var ext = nd.TryGetValue("Extension", out yaml) ? yaml.Value : "aud";
+			Filename = (nd.TryGetValue("Filename", out yaml) ? yaml.Value : key) + "." + ext;
 		}

 		public void Load(IReadOnlyFileSystem fileSystem)
--- a/OpenRA.Game/GameRules/Ruleset.cs
+++ b/OpenRA.Game/GameRules/Ruleset.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -15,20 +15,18 @@ using System.Linq;
 using System.Threading.Tasks;
 using OpenRA.FileSystem;
 using OpenRA.GameRules;
-using OpenRA.Graphics;
 using OpenRA.Traits;

 namespace OpenRA
 {
 	public class Ruleset
 	{
-		public readonly IReadOnlyDictionary<string, ActorInfo> Actors;
+		public readonly ActorInfoDictionary Actors;
 		public readonly IReadOnlyDictionary<string, WeaponInfo> Weapons;
 		public readonly IReadOnlyDictionary<string, SoundInfo> Voices;
 		public readonly IReadOnlyDictionary<string, SoundInfo> Notifications;
 		public readonly IReadOnlyDictionary<string, MusicInfo> Music;
-		public readonly TileSet TileSet;
-		public readonly SequenceProvider Sequences;
+		public readonly ITerrainInfo TerrainInfo;
 		public readonly IReadOnlyDictionary<string, MiniYamlNode> ModelSequences;

 		public Ruleset(
@@ -37,17 +35,15 @@ namespace OpenRA
 			IReadOnlyDictionary<string, SoundInfo> voices,
 			IReadOnlyDictionary<string, SoundInfo> notifications,
 			IReadOnlyDictionary<string, MusicInfo> music,
-			TileSet tileSet,
-			SequenceProvider sequences,
+			ITerrainInfo terrainInfo,
 			IReadOnlyDictionary<string, MiniYamlNode> modelSequences)
 		{
-			Actors = actors;
+			Actors = new ActorInfoDictionary(actors);
 			Weapons = weapons;
 			Voices = voices;
 			Notifications = notifications;
 			Music = music;
-			TileSet = tileSet;
-			Sequences = sequences;
+			TerrainInfo = terrainInfo;
 			ModelSequences = modelSequences;

 			foreach (var a in Actors.Values)
@@ -60,15 +56,14 @@ namespace OpenRA
 					}
 					catch (YamlException e)
 					{
-						throw new YamlException("Actor type {0}: {1}".F(a.Name, e.Message));
+						throw new YamlException($"Actor type {a.Name}: {e.Message}");
 					}
 				}
 			}

 			foreach (var weapon in Weapons)
 			{
-				var projectileLoaded = weapon.Value.Projectile as IRulesetLoaded<WeaponInfo>;
-				if (projectileLoaded != null)
+				if (weapon.Value.Projectile is IRulesetLoaded<WeaponInfo> projectileLoaded)
 				{
 					try
 					{
@@ -76,14 +71,13 @@ namespace OpenRA
 					}
 					catch (YamlException e)
 					{
-						throw new YamlException("Projectile type {0}: {1}".F(weapon.Key, e.Message));
+						throw new YamlException($"Projectile type {weapon.Key}: {e.Message}");
 					}
 				}

 				foreach (var warhead in weapon.Value.Warheads)
 				{
-					var cacher = warhead as IRulesetLoaded<WeaponInfo>;
-					if (cacher != null)
+					if (warhead is IRulesetLoaded<WeaponInfo> cacher)
 					{
 						try
 						{
@@ -91,7 +85,7 @@ namespace OpenRA
 						}
 						catch (YamlException e)
 						{
-							throw new YamlException("Weapon type {0}: {1}".F(weapon.Key, e.Message));
+							throw new YamlException($"Weapon type {weapon.Key}: {e.Message}");
 						}
 					}
 				}
@@ -117,7 +111,7 @@ namespace OpenRA
 			if (filterNode != null)
 				yamlNodes = yamlNodes.Where(k => !filterNode(k));

-			return new ReadOnlyDictionary<string, T>(yamlNodes.ToDictionaryWithConflictLog(k => k.Key.ToLowerInvariant(), makeObject, "LoadFromManifest<" + name + ">"));
+			return yamlNodes.ToDictionaryWithConflictLog(k => k.Key.ToLowerInvariant(), makeObject, "LoadFromManifest<" + name + ">");
 		}

 		public static Ruleset LoadDefaults(ModData modData)
@@ -126,14 +120,14 @@ namespace OpenRA
 			var fs = modData.DefaultFileSystem;

 			Ruleset ruleset = null;
-			Action f = () =>
+			void LoadRuleset()
 			{
 				var actors = MergeOrDefault("Manifest,Rules", fs, m.Rules, null, null,
 					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value),
 					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal));

 				var weapons = MergeOrDefault("Manifest,Weapons", fs, m.Weapons, null, null,
-					k => new WeaponInfo(k.Key.ToLowerInvariant(), k.Value));
+					k => new WeaponInfo(k.Value));

 				var voices = MergeOrDefault("Manifest,Voices", fs, m.Voices, null, null,
 					k => new SoundInfo(k.Value));
@@ -147,15 +141,15 @@ namespace OpenRA
 				var modelSequences = MergeOrDefault("Manifest,ModelSequences", fs, m.ModelSequences, null, null,
 					k => k);

-				// The default ruleset does not include a preferred tileset or sequence set
-				ruleset = new Ruleset(actors, weapons, voices, notifications, music, null, null, modelSequences);
-			};
+				// The default ruleset does not include a preferred tileset
+				ruleset = new Ruleset(actors, weapons, voices, notifications, music, null, modelSequences);
+			}

 			if (modData.IsOnMainThread)
 			{
 				modData.HandleLoadingProgress();

-				var loader = new Task(f);
+				var loader = new Task(LoadRuleset);
 				loader.Start();

 				// Animate the loadscreen while we wait
@@ -163,7 +157,7 @@ namespace OpenRA
 					modData.HandleLoadingProgress();
 			}
 			else
-				f();
+				LoadRuleset();

 			return ruleset;
 		}
@@ -171,28 +165,27 @@ namespace OpenRA
 		public static Ruleset LoadDefaultsForTileSet(ModData modData, string tileSet)
 		{
 			var dr = modData.DefaultRules;
-			var ts = modData.DefaultTileSets[tileSet];
-			var sequences = modData.DefaultSequences[tileSet];
+			var terrainInfo = modData.DefaultTerrainInfo[tileSet];

-			return new Ruleset(dr.Actors, dr.Weapons, dr.Voices, dr.Notifications, dr.Music, ts, sequences, dr.ModelSequences);
+			return new Ruleset(dr.Actors, dr.Weapons, dr.Voices, dr.Notifications, dr.Music, terrainInfo, dr.ModelSequences);
 		}

 		public static Ruleset Load(ModData modData, IReadOnlyFileSystem fileSystem, string tileSet,
 			MiniYaml mapRules, MiniYaml mapWeapons, MiniYaml mapVoices, MiniYaml mapNotifications,
-			MiniYaml mapMusic, MiniYaml mapSequences, MiniYaml mapModelSequences)
+			MiniYaml mapMusic, MiniYaml mapModelSequences)
 		{
 			var m = modData.Manifest;
 			var dr = modData.DefaultRules;

 			Ruleset ruleset = null;
-			Action f = () =>
+			void LoadRuleset()
 			{
 				var actors = MergeOrDefault("Rules", fileSystem, m.Rules, mapRules, dr.Actors,
 					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value),
 					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal));

 				var weapons = MergeOrDefault("Weapons", fileSystem, m.Weapons, mapWeapons, dr.Weapons,
-					k => new WeaponInfo(k.Key.ToLowerInvariant(), k.Value));
+					k => new WeaponInfo(k.Value));

 				var voices = MergeOrDefault("Voices", fileSystem, m.Voices, mapVoices, dr.Voices,
 					k => new SoundInfo(k.Value));
@@ -203,26 +196,22 @@ namespace OpenRA
 				var music = MergeOrDefault("Music", fileSystem, m.Music, mapMusic, dr.Music,
 					k => new MusicInfo(k.Key, k.Value));

-				// TODO: Add support for merging custom tileset modifications
-				var ts = modData.DefaultTileSets[tileSet];
-
-				// TODO: Top-level dictionary should be moved into the Ruleset instead of in its own object
-				var sequences = mapSequences == null ? modData.DefaultSequences[tileSet] :
-					new SequenceProvider(fileSystem, modData, tileSet, mapSequences);
+				// TODO: Add support for merging custom terrain modifications
+				var terrainInfo = modData.DefaultTerrainInfo[tileSet];

 				var modelSequences = dr.ModelSequences;
 				if (mapModelSequences != null)
 					modelSequences = MergeOrDefault("ModelSequences", fileSystem, m.ModelSequences, mapModelSequences, dr.ModelSequences,
 						k => k);

-				ruleset = new Ruleset(actors, weapons, voices, notifications, music, ts, sequences, modelSequences);
-			};
+				ruleset = new Ruleset(actors, weapons, voices, notifications, music, terrainInfo, modelSequences);
+			}

 			if (modData.IsOnMainThread)
 			{
 				modData.HandleLoadingProgress();

-				var loader = new Task(f);
+				var loader = new Task(LoadRuleset);
 				loader.Start();

 				// Animate the loadscreen while we wait
@@ -230,14 +219,14 @@ namespace OpenRA
 					modData.HandleLoadingProgress();
 			}
 			else
-				f();
+				LoadRuleset();

 			return ruleset;
 		}

 		static bool AnyCustomYaml(MiniYaml yaml)
 		{
-			return yaml != null && (yaml.Value != null || yaml.Nodes.Any());
+			return yaml != null && (yaml.Value != null || yaml.Nodes.Count > 0);
 		}

 		static bool AnyFlaggedTraits(ModData modData, List<MiniYamlNode> actors)
@@ -250,12 +239,12 @@ namespace OpenRA
 					{
 						var traitName = traitNode.Key.Split('@')[0];
 						var traitType = modData.ObjectCreator.FindType(traitName + "Info");
-						if (traitType != null && traitType.GetInterface("ILobbyCustomRulesIgnore") == null)
+						if (traitType != null && traitType.GetInterface(nameof(ILobbyCustomRulesIgnore)) == null)
 							return true;
 					}
 					catch (Exception ex)
 					{
-						Log.Write("debug", "Error in AnyFlaggedTraits\r\n" + ex.ToString());
+						Log.Write("debug", "Error in AnyFlaggedTraits\n" + ex.ToString());
 					}
 				}
 			}
--- a/OpenRA.Game/GameRules/SoundInfo.cs
+++ b/OpenRA.Game/GameRules/SoundInfo.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -17,14 +17,14 @@ namespace OpenRA.GameRules
 {
 	public class SoundInfo
 	{
-		public readonly Dictionary<string, string[]> Variants = new Dictionary<string, string[]>();
-		public readonly Dictionary<string, string[]> Prefixes = new Dictionary<string, string[]>();
-		public readonly Dictionary<string, string[]> Voices = new Dictionary<string, string[]>();
-		public readonly Dictionary<string, string[]> Notifications = new Dictionary<string, string[]>();
+		public readonly Dictionary<string, string[]> Variants = new();
+		public readonly Dictionary<string, string[]> Prefixes = new();
+		public readonly Dictionary<string, string[]> Voices = new();
+		public readonly Dictionary<string, string[]> Notifications = new();
 		public readonly string DefaultVariant = ".aud";
 		public readonly string DefaultPrefix = "";
-		public readonly HashSet<string> DisableVariants = new HashSet<string>();
-		public readonly HashSet<string> DisablePrefixes = new HashSet<string>();
+		public readonly HashSet<string> DisableVariants = new();
+		public readonly HashSet<string> DisablePrefixes = new();

 		public readonly Lazy<Dictionary<string, SoundPool>> VoicePools;
 		public readonly Lazy<Dictionary<string, SoundPool>> NotificationsPools;
@@ -33,23 +33,28 @@ namespace OpenRA.GameRules
 		{
 			FieldLoader.Load(this, y);

-			VoicePools = Exts.Lazy(() => Voices.ToDictionary(a => a.Key, a => new SoundPool(1f, a.Value)));
+			VoicePools = Exts.Lazy(() => Voices.ToDictionary(a => a.Key, a => new SoundPool(1f, SoundPool.DefaultInterruptType, a.Value)));
 			NotificationsPools = Exts.Lazy(() => ParseSoundPool(y, "Notifications"));
 		}

-		Dictionary<string, SoundPool> ParseSoundPool(MiniYaml y, string key)
+		static Dictionary<string, SoundPool> ParseSoundPool(MiniYaml y, string key)
 		{
 			var ret = new Dictionary<string, SoundPool>();
 			var classifiction = y.Nodes.First(x => x.Key == key);
 			foreach (var t in classifiction.Value.Nodes)
 			{
 				var volumeModifier = 1f;
-				var volumeModifierNode = t.Value.Nodes.FirstOrDefault(x => x.Key == "VolumeModifier");
+				var volumeModifierNode = t.Value.Nodes.FirstOrDefault(x => x.Key == nameof(SoundPool.VolumeModifier));
 				if (volumeModifierNode != null)
 					volumeModifier = FieldLoader.GetValue<float>(volumeModifierNode.Key, volumeModifierNode.Value.Value);

+				var interruptType = SoundPool.DefaultInterruptType;
+				var interruptTypeNode = t.Value.Nodes.FirstOrDefault(x => x.Key == nameof(SoundPool.InterruptType));
+				if (interruptTypeNode != null)
+					interruptType = FieldLoader.GetValue<SoundPool.InterruptType>(interruptTypeNode.Key, interruptTypeNode.Value.Value);
+
 				var names = FieldLoader.GetValue<string[]>(t.Key, t.Value.Value);
-				var sp = new SoundPool(volumeModifier, names);
+				var sp = new SoundPool(volumeModifier, interruptType, names);
 				ret.Add(t.Key, sp);
 			}

@@ -59,13 +64,17 @@ namespace OpenRA.GameRules

 	public class SoundPool
 	{
+		public enum InterruptType { DoNotPlay, Interrupt, Overlap }
+		public const InterruptType DefaultInterruptType = InterruptType.DoNotPlay;
 		public readonly float VolumeModifier;
+		public readonly InterruptType Type;
 		readonly string[] clips;
-		readonly List<string> liveclips = new List<string>();
+		readonly List<string> liveclips = new();

-		public SoundPool(float volumeModifier, params string[] clips)
+		public SoundPool(float volumeModifier, InterruptType interruptType, params string[] clips)
 		{
 			VolumeModifier = volumeModifier;
+			Type = interruptType;
 			this.clips = clips;
 		}

--- a/OpenRA.Game/GameRules/WeaponInfo.cs
+++ b/OpenRA.Game/GameRules/WeaponInfo.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -36,7 +36,7 @@ namespace OpenRA.GameRules
 	public class WarheadArgs
 	{
 		public WeaponInfo Weapon;
-		public int[] DamageModifiers = { };
+		public int[] DamageModifiers = Array.Empty<int>();
 		public WPos? Source;
 		public WRot ImpactOrientation;
 		public WPos ImpactPosition;
@@ -99,17 +99,20 @@ namespace OpenRA.GameRules
 		[Desc("Number of shots in a single ammo magazine.")]
 		public readonly int Burst = 1;

+		[Desc("Can this weapon target the attacker itself?")]
+		public readonly bool CanTargetSelf = false;
+
 		[Desc("What types of targets are affected.")]
-		public readonly BitSet<TargetableType> ValidTargets = new BitSet<TargetableType>("Ground", "Water");
+		public readonly BitSet<TargetableType> ValidTargets = new("Ground", "Water");

 		[Desc("What types of targets are unaffected.", "Overrules ValidTargets.")]
 		public readonly BitSet<TargetableType> InvalidTargets;

-		static readonly BitSet<TargetableType> TargetTypeAir = new BitSet<TargetableType>("Air");
+		static readonly BitSet<TargetableType> TargetTypeAir = new("Air");

 		[Desc("If weapon is not directly targeting an actor and targeted position is above this altitude,",
 			"the weapon will ignore terrain target types and only check TargetTypeAir for validity.")]
-		public readonly WDist AirThreshold = new WDist(128);
+		public readonly WDist AirThreshold = new(128);

 		[Desc("Delay in ticks between firing shots from the same ammo magazine. If one entry, it will be used for all bursts.",
 			"If multiple entries, their number needs to match Burst - 1.")]
@@ -121,13 +124,18 @@ namespace OpenRA.GameRules
 		[Desc("Does this weapon aim at the target's center regardless of other targetable offsets?")]
 		public readonly bool TargetActorCenter = false;

-		[FieldLoader.LoadUsing("LoadProjectile")]
+		[FieldLoader.LoadUsing(nameof(LoadProjectile))]
 		public readonly IProjectileInfo Projectile;

-		[FieldLoader.LoadUsing("LoadWarheads")]
-		public readonly List<IWarhead> Warheads = new List<IWarhead>();
+		[FieldLoader.LoadUsing(nameof(LoadWarheads))]
+		public readonly List<IWarhead> Warheads = new();

-		public WeaponInfo(string name, MiniYaml content)
+		/// <summary>
+		/// This constructor is used solely for documentation generation.
+		/// </summary>
+		public WeaponInfo() { }
+
+		public WeaponInfo(MiniYaml content)
 		{
 			// Resolve any weapon-level yaml inheritance or removals
 			// HACK: The "Defaults" sequence syntax prevents us from doing this generally during yaml parsing
@@ -139,7 +147,11 @@ namespace OpenRA.GameRules
 		{
 			if (!yaml.ToDictionary().TryGetValue("Projectile", out var proj))
 				return null;
+
 			var ret = Game.CreateObject<IProjectileInfo>(proj.Value + "Info");
+			if (ret == null)
+				return null;
+
 			FieldLoader.Load(ret, proj);
 			return ret;
 		}
@@ -150,6 +162,9 @@ namespace OpenRA.GameRules
 			foreach (var node in yaml.Nodes.Where(n => n.Key.StartsWith("Warhead")))
 			{
 				var ret = Game.CreateObject<IWarhead>(node.Value.Value + "Warhead");
+				if (ret == null)
+					continue;
+
 				FieldLoader.Load(ret, node.Value);
 				retList.Add(ret);
 			}
@@ -194,29 +209,24 @@ namespace OpenRA.GameRules
 		/// <summary>Checks if the weapon is valid against (can target) the actor.</summary>
 		public bool IsValidAgainst(Actor victim, Actor firedBy)
 		{
-			var targetTypes = victim.GetEnabledTargetTypes();
-
-			if (!IsValidTarget(targetTypes))
+			if (!CanTargetSelf && victim == firedBy)
 				return false;

-			// PERF: Avoid LINQ.
-			foreach (var warhead in Warheads)
-				if (warhead.IsValidAgainst(victim, firedBy))
-					return true;
+			var targetTypes = victim.GetEnabledTargetTypes();

-			return false;
+			return IsValidTarget(targetTypes);
 		}

 		/// <summary>Checks if the weapon is valid against (can target) the frozen actor.</summary>
 		public bool IsValidAgainst(FrozenActor victim, Actor firedBy)
 		{
-			if (!IsValidTarget(victim.TargetTypes))
+			if (!victim.IsValid)
 				return false;

-			if (!Warheads.Any(w => w.IsValidAgainst(victim, firedBy)))
+			if (!CanTargetSelf && victim.Actor == firedBy)
 				return false;

-			return true;
+			return IsValidTarget(victim.TargetTypes);
 		}

 		/// <summary>Applies all the weapon's warheads to the target.</summary>
--- a/OpenRA.Game/GameSpeed.cs
+++ b/OpenRA.Game/GameSpeed.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -10,27 +10,50 @@
 #endregion

 using System.Collections.Generic;
+using System.Linq;

 namespace OpenRA
 {
 	public class GameSpeed
 	{
-		[Translate]
-		public readonly string Name = "Default";
-		public readonly int Timestep = 40;
-		public readonly int OrderLatency = 3;
+		[TranslationReference]
+		[FieldLoader.Require]
+		public readonly string Name;
+
+		[FieldLoader.Require]
+		public readonly int Timestep;
+
+		[FieldLoader.Require]
+		public readonly int OrderLatency;
 	}

 	public class GameSpeeds : IGlobalModData
 	{
-		[FieldLoader.LoadUsing("LoadSpeeds")]
+		[FieldLoader.Require]
+		public readonly string DefaultSpeed;
+
+		[FieldLoader.LoadUsing(nameof(LoadSpeeds))]
 		public readonly Dictionary<string, GameSpeed> Speeds;

 		static object LoadSpeeds(MiniYaml y)
 		{
 			var ret = new Dictionary<string, GameSpeed>();
-			foreach (var node in y.Nodes)
-				ret.Add(node.Key, FieldLoader.Load<GameSpeed>(node.Value));
+			var speedsNode = y.Nodes.FirstOrDefault(n => n.Key == "Speeds");
+			if (speedsNode == null)
+				throw new YamlException("Error parsing GameSpeeds: Missing Speeds node!");
+
+			foreach (var node in speedsNode.Value.Nodes)
+			{
+				try
+				{
+					ret.Add(node.Key, FieldLoader.Load<GameSpeed>(node.Value));
+				}
+				catch (FieldLoader.MissingFieldsException e)
+				{
+					var label = e.Missing.Length > 1 ? "Required properties missing" : "Required property missing";
+					throw new YamlException($"Error parsing GameSpeed {node.Key}: {label}: {e.Missing.JoinWith(", ")}");
+				}
+			}

 			return ret;
 		}
--- a/OpenRA.Game/Graphics/Animation.cs
+++ b/OpenRA.Game/Graphics/Animation.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -22,7 +22,7 @@ namespace OpenRA.Graphics
 		public string Name { get; private set; }
 		public bool IsDecoration { get; set; }

-		readonly SequenceProvider sequenceProvider;
+		readonly SequenceSet sequences;
 		readonly Func<WAngle> facingFunc;
 		readonly Func<bool> paused;

@@ -30,7 +30,7 @@ namespace OpenRA.Graphics
 		bool backwards;
 		bool tickAlways;
 		int timeUntilNextFrame;
-		Action tickFunc = () => { };
+		Action tickFunc;

 		public Animation(World world, string name)
 			: this(world, name, () => WAngle.Zero) { }
@@ -43,48 +43,57 @@ namespace OpenRA.Graphics

 		public Animation(World world, string name, Func<WAngle> facingFunc, Func<bool> paused)
 		{
-			sequenceProvider = world.Map.Rules.Sequences;
+			sequences = world.Map.Sequences;
 			Name = name.ToLowerInvariant();
 			this.facingFunc = facingFunc;
 			this.paused = paused;
 		}

-		public int CurrentFrame { get { return backwards ? CurrentSequence.Length - frame - 1 : frame; } }
-		public Sprite Image { get { return CurrentSequence.GetSprite(CurrentFrame, facingFunc()); } }
+		public int CurrentFrame => backwards ? CurrentSequence.Length - frame - 1 : frame;

-		public IRenderable[] Render(WPos pos, WVec offset, int zOffset, PaletteReference palette, float scale)
+		public Sprite Image => CurrentSequence.GetSprite(CurrentFrame, facingFunc());
+
+		public IRenderable[] Render(WPos pos, in WVec offset, int zOffset, PaletteReference palette)
 		{
-			var imageRenderable = new SpriteRenderable(Image, pos, offset, CurrentSequence.ZOffset + zOffset, palette, scale, IsDecoration, CurrentSequence.IgnoreWorldTint);
+			var tintModifiers = CurrentSequence.IgnoreWorldTint ? TintModifiers.IgnoreWorldTint : TintModifiers.None;
+			var alpha = CurrentSequence.GetAlpha(CurrentFrame);
+			var (image, rotation) = CurrentSequence.GetSpriteWithRotation(CurrentFrame, facingFunc());
+			var imageRenderable = new SpriteRenderable(image, pos, offset, CurrentSequence.ZOffset + zOffset, palette, CurrentSequence.Scale, alpha, float3.Ones, tintModifiers, IsDecoration,
+				rotation);

-			if (CurrentSequence.ShadowStart >= 0)
+			var shadow = CurrentSequence.GetShadow(CurrentFrame, facingFunc());
+			if (shadow != null)
 			{
-				var shadow = CurrentSequence.GetShadow(CurrentFrame, facingFunc());
-				var shadowRenderable = new SpriteRenderable(shadow, pos, offset, CurrentSequence.ShadowZOffset + zOffset, palette, scale, true, CurrentSequence.IgnoreWorldTint);
+				var shadowRenderable = new SpriteRenderable(shadow, pos, offset, CurrentSequence.ShadowZOffset + zOffset, palette, CurrentSequence.Scale, 1f, float3.Ones, tintModifiers,
+					true, rotation);
 				return new IRenderable[] { shadowRenderable, imageRenderable };
 			}

 			return new IRenderable[] { imageRenderable };
 		}

-		public IRenderable[] RenderUI(WorldRenderer wr, int2 pos, WVec offset, int zOffset, PaletteReference palette, float scale)
+		public IRenderable[] RenderUI(WorldRenderer wr, int2 pos, in WVec offset, int zOffset, PaletteReference palette, float scale = 1f, float rotation = 0f)
 		{
+			scale *= CurrentSequence.Scale;
 			var screenOffset = (scale * wr.ScreenVectorComponents(offset)).XY.ToInt2();
 			var imagePos = pos + screenOffset - new int2((int)(scale * Image.Size.X / 2), (int)(scale * Image.Size.Y / 2));
-			var imageRenderable = new UISpriteRenderable(Image, WPos.Zero + offset, imagePos, CurrentSequence.ZOffset + zOffset, palette, scale);
+			var alpha = CurrentSequence.GetAlpha(CurrentFrame);
+			var imageRenderable = new UISpriteRenderable(Image, WPos.Zero + offset, imagePos, CurrentSequence.ZOffset + zOffset, palette, scale, alpha, rotation);

-			if (CurrentSequence.ShadowStart >= 0)
+			var shadow = CurrentSequence.GetShadow(CurrentFrame, facingFunc());
+			if (shadow != null)
 			{
-				var shadow = CurrentSequence.GetShadow(CurrentFrame, facingFunc());
 				var shadowPos = pos - new int2((int)(scale * shadow.Size.X / 2), (int)(scale * shadow.Size.Y / 2));
-				var shadowRenderable = new UISpriteRenderable(shadow, WPos.Zero + offset, shadowPos, CurrentSequence.ShadowZOffset + zOffset, palette, scale);
+				var shadowRenderable = new UISpriteRenderable(shadow, WPos.Zero + offset, shadowPos, CurrentSequence.ShadowZOffset + zOffset, palette, scale, 1f, rotation);
 				return new IRenderable[] { shadowRenderable, imageRenderable };
 			}

 			return new IRenderable[] { imageRenderable };
 		}

-		public Rectangle ScreenBounds(WorldRenderer wr, WPos pos, WVec offset, float scale)
+		public Rectangle ScreenBounds(WorldRenderer wr, WPos pos, in WVec offset)
 		{
+			var scale = CurrentSequence.Scale;
 			var xy = wr.ScreenPxPosition(pos) + wr.ScreenPxOffset(offset);
 			var cb = CurrentSequence.Bounds;
 			return Rectangle.FromLTRB(
@@ -96,7 +105,7 @@ namespace OpenRA.Graphics

 		public IRenderable[] Render(WPos pos, PaletteReference palette)
 		{
-			return Render(pos, WVec.Zero, 0, palette, 1f);
+			return Render(pos, WVec.Zero, 0, palette);
 		}

 		public void Play(string sequenceName)
@@ -107,7 +116,7 @@ namespace OpenRA.Graphics
 		int CurrentSequenceTickOrDefault()
 		{
 			const int DefaultTick = 40; // 25 fps == 40 ms
-			return CurrentSequence != null ? CurrentSequence.Tick : DefaultTick;
+			return CurrentSequence?.Tick ?? DefaultTick;
 		}

 		void PlaySequence(string sequenceName)
@@ -155,7 +164,7 @@ namespace OpenRA.Graphics
 				if (frame >= CurrentSequence.Length)
 				{
 					frame = CurrentSequence.Length - 1;
-					tickFunc = () => { };
+					tickFunc = null;
 					after?.Invoke();
 				}
 			};
@@ -203,13 +212,13 @@ namespace OpenRA.Graphics
 		public void Tick(int t)
 		{
 			if (tickAlways)
-				tickFunc();
+				tickFunc?.Invoke();
 			else
 			{
 				timeUntilNextFrame -= t;
 				while (timeUntilNextFrame <= 0)
 				{
-					tickFunc();
+					tickFunc?.Invoke();
 					timeUntilNextFrame += CurrentSequenceTickOrDefault();
 				}
 			}
@@ -227,11 +236,11 @@ namespace OpenRA.Graphics
 			}
 		}

-		public bool HasSequence(string seq) { return sequenceProvider.HasSequence(Name, seq); }
+		public bool HasSequence(string seq) { return sequences.HasSequence(Name, seq); }

 		public ISpriteSequence GetSequence(string sequenceName)
 		{
-			return sequenceProvider.GetSequence(Name, sequenceName);
+			return sequences.GetSequence(Name, sequenceName);
 		}

 		public string GetRandomExistingSequence(string[] sequences, MersenneTwister random)
--- a/OpenRA.Game/Graphics/AnimationWithOffset.cs
+++ b/OpenRA.Game/Graphics/AnimationWithOffset.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -35,21 +35,21 @@ namespace OpenRA.Graphics
 			ZOffset = zOffset;
 		}

-		public IRenderable[] Render(Actor self, WorldRenderer wr, PaletteReference pal, float scale)
+		public IRenderable[] Render(Actor self, PaletteReference pal)
 		{
 			var center = self.CenterPosition;
-			var offset = OffsetFunc != null ? OffsetFunc() : WVec.Zero;
+			var offset = OffsetFunc?.Invoke() ?? WVec.Zero;

-			var z = (ZOffset != null) ? ZOffset(center + offset) : 0;
-			return Animation.Render(center, offset, z, pal, scale);
+			var z = ZOffset?.Invoke(center + offset) ?? 0;
+			return Animation.Render(center, offset, z, pal);
 		}

-		public Rectangle ScreenBounds(Actor self, WorldRenderer wr, float scale)
+		public Rectangle ScreenBounds(Actor self, WorldRenderer wr)
 		{
 			var center = self.CenterPosition;
-			var offset = OffsetFunc != null ? OffsetFunc() : WVec.Zero;
+			var offset = OffsetFunc?.Invoke() ?? WVec.Zero;

-			return Animation.ScreenBounds(wr, center, offset, scale);
+			return Animation.ScreenBounds(wr, center, offset);
 		}

 		public static implicit operator AnimationWithOffset(Animation a)
--- a/OpenRA.Game/Graphics/ChromeProvider.cs
+++ b/OpenRA.Game/Graphics/ChromeProvider.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -49,10 +49,10 @@ namespace OpenRA.Graphics

 			public readonly int[] PanelRegion = null;
 			public readonly PanelSides PanelSides = PanelSides.All;
-			public readonly Dictionary<string, Rectangle> Regions = new Dictionary<string, Rectangle>();
+			public readonly Dictionary<string, Rectangle> Regions = new();
 		}

-		public static IReadOnlyDictionary<string, Collection> Collections { get; private set; }
+		public static IReadOnlyDictionary<string, Collection> Collections => collections;
 		static Dictionary<string, Collection> collections;
 		static Dictionary<string, (Sheet Sheet, int Density)> cachedSheets;
 		static Dictionary<string, Dictionary<string, Sprite>> cachedSprites;
@@ -77,8 +77,6 @@ namespace OpenRA.Graphics
 			cachedPanelSprites = new Dictionary<string, Sprite[]>();
 			cachedCollectionSheets = new Dictionary<Collection, (Sheet, int)>();

-			Collections = new ReadOnlyDictionary<string, Collection>(collections);
-
 			var chrome = MiniYaml.Merge(modData.Manifest.Chrome
 				.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s)));

@@ -102,9 +100,7 @@ namespace OpenRA.Graphics

 		static void LoadCollection(string name, MiniYaml yaml)
 		{
-			if (Game.ModData.LoadScreen != null)
-				Game.ModData.LoadScreen.Display();
-
+			Game.ModData.LoadScreen?.Display();
 			collections.Add(name, FieldLoader.Load<Collection>(yaml));
 		}

@@ -146,6 +142,15 @@ namespace OpenRA.Graphics
 		}

 		public static Sprite GetImage(string collectionName, string imageName)
+		{
+			var image = TryGetImage(collectionName, imageName);
+			if (image == null)
+				throw new ArgumentException($"Sprite `{collectionName}/{imageName}` was not found.");
+
+			return image;
+		}
+
+		public static Sprite TryGetImage(string collectionName, string imageName)
 		{
 			if (string.IsNullOrEmpty(collectionName))
 				return null;
@@ -155,10 +160,7 @@ namespace OpenRA.Graphics
 				return sprite;

 			if (!collections.TryGetValue(collectionName, out var collection))
-			{
-				Log.Write("debug", "Could not find collection '{0}'", collectionName);
 				return null;
-			}

 			if (!collection.Regions.TryGetValue(imageName, out var mi))
 				return null;
@@ -178,6 +180,15 @@ namespace OpenRA.Graphics
 		}

 		public static Sprite[] GetPanelImages(string collectionName)
+		{
+			var panel = TryGetPanelImages(collectionName);
+			if (panel == null)
+				throw new ArgumentException($"Panel `{collectionName}` was not found.");
+
+			return panel;
+		}
+
+		public static Sprite[] TryGetPanelImages(string collectionName)
 		{
 			if (string.IsNullOrEmpty(collectionName))
 				return null;
@@ -187,17 +198,14 @@ namespace OpenRA.Graphics
 				return cachedSprites;

 			if (!collections.TryGetValue(collectionName, out var collection))
-			{
-				Log.Write("debug", "Could not find collection '{0}'", collectionName);
 				return null;
-			}

 			Sprite[] sprites;
 			if (collection.PanelRegion != null)
 			{
 				if (collection.PanelRegion.Length != 8)
 				{
-					Log.Write("debug", "Collection '{0}' does not define a valid PanelRegion", collectionName);
+					Log.Write("debug", $"Collection '{collectionName}' does not define a valid PanelRegion");
 					return null;
 				}

@@ -224,18 +232,23 @@ namespace OpenRA.Graphics
 			}
 			else
 			{
+				// PERF: We don't need to search for images if there are no definitions.
+				// PERF: It's more efficient to send an empty array rather than an array of 9 nulls.
+				if (!collection.Regions.Any())
+					return Array.Empty<Sprite>();
+
 				// Support manual definitions for unusual dialog layouts
 				sprites = new[]
 				{
-					GetImage(collectionName, "corner-tl"),
-					GetImage(collectionName, "border-t"),
-					GetImage(collectionName, "corner-tr"),
-					GetImage(collectionName, "border-l"),
-					GetImage(collectionName, "background"),
-					GetImage(collectionName, "border-r"),
-					GetImage(collectionName, "corner-bl"),
-					GetImage(collectionName, "border-b"),
-					GetImage(collectionName, "corner-br")
+					TryGetImage(collectionName, "corner-tl"),
+					TryGetImage(collectionName, "border-t"),
+					TryGetImage(collectionName, "corner-tr"),
+					TryGetImage(collectionName, "border-l"),
+					TryGetImage(collectionName, "background"),
+					TryGetImage(collectionName, "border-r"),
+					TryGetImage(collectionName, "corner-bl"),
+					TryGetImage(collectionName, "border-b"),
+					TryGetImage(collectionName, "corner-br")
 				};
 			}

@@ -250,13 +263,13 @@ namespace OpenRA.Graphics

 			if (!collections.TryGetValue(collectionName, out var collection))
 			{
-				Log.Write("debug", "Could not find collection '{0}'", collectionName);
+				Log.Write("debug", $"Could not find collection '{collectionName}'");
 				return new Size(0, 0);
 			}

 			if (collection.PanelRegion == null || collection.PanelRegion.Length != 8)
 			{
-				Log.Write("debug", "Collection '{0}' does not define a valid PanelRegion", collectionName);
+				Log.Write("debug", $"Collection '{collectionName}' does not define a valid PanelRegion");
 				return new Size(0, 0);
 			}

--- a/OpenRA.Game/Graphics/CursorManager.cs
+++ b/OpenRA.Game/Graphics/CursorManager.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -17,7 +17,7 @@ namespace OpenRA.Graphics
 {
 	public sealed class CursorManager
 	{
-		class Cursor
+		sealed class Cursor
 		{
 			public string Name;
 			public int2 PaddedSize;
@@ -28,14 +28,14 @@ namespace OpenRA.Graphics
 			public IHardwareCursor[] Cursors;
 		}

-		readonly Dictionary<string, Cursor> cursors = new Dictionary<string, Cursor>();
+		readonly Dictionary<string, Cursor> cursors = new();
 		readonly SheetBuilder sheetBuilder;
 		readonly GraphicSettings graphicSettings;

 		Cursor cursor;
 		bool isLocked = false;
 		int2 lockedPosition;
-		bool hardwareCursorsDisabled = false;
+		readonly bool hardwareCursorsDisabled = false;
 		bool hardwareCursorsDoubled = false;

 		public CursorManager(CursorProvider cursorProvider)
@@ -69,9 +69,16 @@ namespace OpenRA.Graphics
 					// Hotspot is specified relative to the center of the frame
 					var hotspot = f.Offset.ToInt2() - kv.Value.Hotspot - new int2(f.Size) / 2;

-					// SheetBuilder expects data in BGRA
-					var data = FrameToBGRA(kv.Key, f, palette);
-					c.Sprites[c.Length++] = sheetBuilder.Add(data, f.Size, 0, hotspot);
+					// Resolve indexed data to real colours
+					var data = f.Data;
+					var type = f.Type;
+					if (type == SpriteFrameType.Indexed8)
+					{
+						data = ConvertIndexedToBgra(kv.Key, f, palette);
+						type = SpriteFrameType.Bgra32;
+					}
+
+					c.Sprites[c.Length++] = sheetBuilder.Add(data, type, f.Size, 0, hotspot);

 					// Bounds relative to the hotspot
 					c.Bounds = Rectangle.Union(c.Bounds, new Rectangle(hotspot, f.Size));
@@ -99,34 +106,27 @@ namespace OpenRA.Graphics
 			// Dispose any existing cursors to avoid leaking native resources
 			ClearHardwareCursors();

-			try
+			foreach (var kv in cursors)
 			{
-				foreach (var kv in cursors)
+				var template = kv.Value;
+				for (var i = 0; i < template.Sprites.Length; i++)
 				{
-					var template = kv.Value;
-					for (var i = 0; i < template.Sprites.Length; i++)
+					template.Cursors[i]?.Dispose();
+
+					// Calculate the padding to position the frame within sequenceBounds
+					var paddingTL = -(template.Bounds.Location - template.Sprites[i].Offset.XY.ToInt2());
+					var paddingBR = template.PaddedSize - new int2(template.Sprites[i].Bounds.Size) - paddingTL;
+
+					var hardwareCursor = CreateHardwareCursor(kv.Key, template.Sprites[i], paddingTL, paddingBR, -template.Bounds.Location);
+					if (hardwareCursor != null)
+						template.Cursors[i] = hardwareCursor;
+					else
 					{
-						if (template.Cursors[i] != null)
-							template.Cursors[i].Dispose();
-
-						// Calculate the padding to position the frame within sequenceBounds
-						var paddingTL = -(template.Bounds.Location - template.Sprites[i].Offset.XY.ToInt2());
-						var paddingBR = template.PaddedSize - new int2(template.Sprites[i].Bounds.Size) - paddingTL;
-
-						template.Cursors[i] = CreateHardwareCursor(kv.Key, template.Sprites[i], paddingTL, paddingBR, -template.Bounds.Location);
+						Log.Write("debug", $"Failed to initialize hardware cursor for {template.Name}.");
+						Console.WriteLine($"Failed to initialize hardware cursor for {template.Name}.");
 					}
 				}
 			}
-			catch (Exception e)
-			{
-				Log.Write("debug", "Failed to initialize hardware cursors. Falling back to software cursors.");
-				Log.Write("debug", "Error was: " + e.Message);
-
-				Console.WriteLine("Failed to initialize hardware cursors. Falling back to software cursors.");
-				Console.WriteLine("Error was: " + e.Message);
-
-				ClearHardwareCursors();
-			}

 			hardwareCursorsDoubled = graphicSettings.CursorDouble;
 		}
@@ -170,10 +170,11 @@ namespace OpenRA.Graphics
 			if (cursor != null && frame >= cursor.Cursors.Length)
 				frame %= cursor.Cursors.Length;

-			if (cursor == null || isLocked)
+			var hardwareCursor = cursor?.Cursors[frame];
+			if (hardwareCursor == null || isLocked)
 				Game.Renderer.Window.SetHardwareCursor(null);
 			else
-				Game.Renderer.Window.SetHardwareCursor(cursor.Cursors[frame]);
+				Game.Renderer.Window.SetHardwareCursor(hardwareCursor);
 		}

 		public void Render(Renderer renderer)
@@ -189,17 +190,17 @@ namespace OpenRA.Graphics
 			// Render cursor in software
 			var doubleCursor = graphicSettings.CursorDouble;
 			var cursorSprite = cursor.Sprites[frame % cursor.Length];
-			var cursorSize = doubleCursor ? 2.0f * cursorSprite.Size : cursorSprite.Size;
+			var cursorScale = doubleCursor ? 2 : 1;

 			// Cursor is rendered in native window coordinates
 			// Apply same scaling rules as hardware cursors
 			if (Game.Renderer.NativeWindowScale > 1.5f)
-				cursorSize = 2 * cursorSize;
+				cursorScale *= 2;

 			var mousePos = isLocked ? lockedPosition : Viewport.LastMousePos;
 			renderer.RgbaSpriteRenderer.DrawSprite(cursorSprite,
 				mousePos,
-				cursorSize / Game.Renderer.WindowScale);
+				cursorScale / Game.Renderer.WindowScale);
 		}

 		public void Lock()
@@ -217,33 +218,27 @@ namespace OpenRA.Graphics
 			Update();
 		}

-		public static byte[] FrameToBGRA(string name, ISpriteFrame frame, ImmutablePalette palette)
+		public static byte[] ConvertIndexedToBgra(string name, ISpriteFrame frame, ImmutablePalette palette)
 		{
-			// Data is already in BGRA format
-			if (frame.Type == SpriteFrameType.BGRA)
-				return frame.Data;
+			if (frame.Type != SpriteFrameType.Indexed8)
+				throw new ArgumentException("ConvertIndexedToBgra requires input frames to be indexed.", nameof(frame));

-			// Cursors may be either native BGRA or Indexed.
-			// Indexed sprites are converted to BGRA using the referenced palette.
 			// All palettes must be explicitly referenced, even if they are embedded in the sprite.
-			if (frame.Type == SpriteFrameType.Indexed && palette == null)
-				throw new InvalidOperationException("Cursor sequence `{0}` attempted to load an indexed sprite but does not define Palette".F(name));
+			if (palette == null)
+				throw new InvalidOperationException($"Cursor sequence `{name}` attempted to load an indexed sprite but does not define Palette");

 			var width = frame.Size.Width;
 			var height = frame.Size.Height;
 			var data = new byte[4 * width * height];
-			for (var j = 0; j < height; j++)
+			unsafe
 			{
-				for (var i = 0; i < width; i++)
+				// Cast the data to an int array so we can copy the src data directly
+				fixed (byte* bd = &data[0])
 				{
-					var rgba = palette[frame.Data[j * width + i]];
-					var k = 4 * (j * width + i);
-
-					// Convert RGBA to BGRA
-					data[k] = (byte)(rgba >> 16);
-					data[k + 1] = (byte)(rgba >> 8);
-					data[k + 2] = (byte)(rgba >> 0);
-					data[k + 3] = (byte)(rgba >> 24);
+					var rgba = (uint*)bd;
+					for (var j = 0; j < height; j++)
+						for (var i = 0; i < width; i++)
+							rgba[j * width + i] = palette[frame.Data[j * width + i]];
 				}
 			}

--- a/OpenRA.Game/Graphics/CursorProvider.cs
+++ b/OpenRA.Game/Graphics/CursorProvider.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -31,15 +31,14 @@ namespace OpenRA.Graphics

 			// Overwrite previous definitions if there are duplicates
 			var pals = new Dictionary<string, IProvidesCursorPaletteInfo>();
-			foreach (var p in modData.DefaultRules.Actors["world"].TraitInfos<IProvidesCursorPaletteInfo>())
+			foreach (var p in modData.DefaultRules.Actors[SystemActors.World].TraitInfos<IProvidesCursorPaletteInfo>())
 				if (p.Palette != null)
 					pals[p.Palette] = p;

 			Palettes = nodesDict["Cursors"].Nodes.Select(n => n.Value.Value)
 				.Where(p => p != null)
 				.Distinct()
-				.ToDictionary(p => p, p => pals[p].ReadPalette(modData.DefaultFileSystem))
-				.AsReadOnly();
+				.ToDictionary(p => p, p => pals[p].ReadPalette(modData.DefaultFileSystem));

 			var frameCache = new FrameCache(fileSystem, modData.SpriteLoaders);
 			var cursors = new Dictionary<string, CursorSequence>();
@@ -47,7 +46,7 @@ namespace OpenRA.Graphics
 				foreach (var sequence in s.Value.Nodes)
 					cursors.Add(sequence.Key, new CursorSequence(frameCache, sequence.Key, s.Key, s.Value.Value, sequence.Value));

-			Cursors = cursors.AsReadOnly();
+			Cursors = cursors;
 		}

 		public bool HasCursorSequence(string cursor)
@@ -60,7 +59,7 @@ namespace OpenRA.Graphics
 			try { return Cursors[cursor]; }
 			catch (KeyNotFoundException)
 			{
-				throw new InvalidOperationException("Cursor does not have a sequence `{0}`".F(cursor));
+				throw new InvalidOperationException($"Cursor does not have a sequence `{cursor}`");
 			}
 		}
 	}
--- a/OpenRA.Game/Graphics/CursorSequence.cs
+++ b/OpenRA.Game/Graphics/CursorSequence.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -31,28 +31,36 @@ namespace OpenRA.Graphics
 			Palette = palette;
 			Name = name;

-			Frames = cache[cursorSrc].Skip(Start).ToArray();
+			var cursorSprites = cache[cursorSrc];
+			Frames = cursorSprites.Skip(Start).ToArray();

-			if ((d.ContainsKey("Length") && d["Length"].Value == "*") || (d.ContainsKey("End") && d["End"].Value == "*"))
+			if ((d.TryGetValue("Length", out var yaml) && yaml.Value == "*") ||
+				(d.TryGetValue("End", out yaml) && yaml.Value == "*"))
 				Length = Frames.Length;
-			else if (d.ContainsKey("Length"))
-				Length = Exts.ParseIntegerInvariant(d["Length"].Value);
-			else if (d.ContainsKey("End"))
-				Length = Exts.ParseIntegerInvariant(d["End"].Value) - Start;
+			else if (d.TryGetValue("Length", out yaml))
+				Length = Exts.ParseIntegerInvariant(yaml.Value);
+			else if (d.TryGetValue("End", out yaml))
+				Length = Exts.ParseIntegerInvariant(yaml.Value) - Start;
 			else
 				Length = 1;

 			Frames = Frames.Take(Length).ToArray();

-			if (d.ContainsKey("X"))
+			if (Start > cursorSprites.Length)
+				throw new YamlException($"Cursor {name}: {nameof(Start)} is greater than the length of the sprite sequence.");
+
+			if (Length > cursorSprites.Length)
+				throw new YamlException($"Cursor {name}: {nameof(Length)} is greater than the length of the sprite sequence.");
+
+			if (d.TryGetValue("X", out yaml))
 			{
-				Exts.TryParseIntegerInvariant(d["X"].Value, out var x);
+				Exts.TryParseIntegerInvariant(yaml.Value, out var x);
 				Hotspot = Hotspot.WithX(x);
 			}

-			if (d.ContainsKey("Y"))
+			if (d.TryGetValue("Y", out yaml))
 			{
-				Exts.TryParseIntegerInvariant(d["Y"].Value, out var y);
+				Exts.TryParseIntegerInvariant(yaml.Value, out var y);
 				Hotspot = Hotspot.WithY(y);
 			}
 		}
--- a/OpenRA.Game/Graphics/HardwarePalette.cs
+++ b/OpenRA.Game/Graphics/HardwarePalette.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -17,73 +17,98 @@ namespace OpenRA.Graphics
 {
 	public sealed class HardwarePalette : IDisposable
 	{
-		public ITexture Texture { get; private set; }
+		public ITexture Texture { get; }
+		public ITexture ColorShifts { get; }
+
 		public int Height { get; private set; }
-		readonly Dictionary<string, ImmutablePalette> palettes = new Dictionary<string, ImmutablePalette>();
-		readonly Dictionary<string, MutablePalette> modifiablePalettes = new Dictionary<string, MutablePalette>();
-		readonly IReadOnlyDictionary<string, MutablePalette> readOnlyModifiablePalettes;
-		readonly Dictionary<string, int> indices = new Dictionary<string, int>();
-		byte[] buffer = new byte[0];
+		readonly Dictionary<string, ImmutablePalette> palettes = new();
+		readonly Dictionary<string, MutablePalette> mutablePalettes = new();
+		readonly Dictionary<string, int> indices = new();
+		byte[] buffer = Array.Empty<byte>();
+		float[] colorShiftBuffer = Array.Empty<float>();

 		public HardwarePalette()
 		{
 			Texture = Game.Renderer.Context.CreateTexture();
-			readOnlyModifiablePalettes = modifiablePalettes.AsReadOnly();
+			ColorShifts = Game.Renderer.Context.CreateTexture();
 		}

 		public bool Contains(string name)
 		{
-			return modifiablePalettes.ContainsKey(name) || palettes.ContainsKey(name);
+			return mutablePalettes.ContainsKey(name) || palettes.ContainsKey(name);
 		}

 		public IPalette GetPalette(string name)
 		{
-			if (modifiablePalettes.TryGetValue(name, out var mutable))
+			if (mutablePalettes.TryGetValue(name, out var mutable))
 				return mutable.AsReadOnly();
 			if (palettes.TryGetValue(name, out var immutable))
 				return immutable;
-			throw new InvalidOperationException("Palette `{0}` does not exist".F(name));
+			throw new InvalidOperationException($"Palette `{name}` does not exist");
 		}

 		public int GetPaletteIndex(string name)
 		{
 			if (!indices.TryGetValue(name, out var ret))
-				throw new InvalidOperationException("Palette `{0}` does not exist".F(name));
+				throw new InvalidOperationException($"Palette `{name}` does not exist");
 			return ret;
 		}

 		public void AddPalette(string name, ImmutablePalette p, bool allowModifiers)
 		{
 			if (palettes.ContainsKey(name))
-				throw new InvalidOperationException("Palette {0} has already been defined".F(name));
+				throw new InvalidOperationException($"Palette {name} has already been defined");

-			int index = palettes.Count;
+			// PERF: the first row in the palette textures is reserved as a placeholder for non-indexed sprites
+			// that do not have a color-shift applied. This provides a quick shortcut to avoid querying the
+			// color-shift texture for every pixel only to find that most are not shifted.
+			var index = palettes.Count + 1;
 			indices.Add(name, index);
 			palettes.Add(name, p);

-			if (palettes.Count > Height)
+			if (index >= Height)
 			{
-				Height = Exts.NextPowerOf2(palettes.Count);
+				Height = Exts.NextPowerOf2(index + 1);
 				Array.Resize(ref buffer, Height * Palette.Size * 4);
+				Array.Resize(ref colorShiftBuffer, Height * 8);
 			}

 			if (allowModifiers)
-				modifiablePalettes.Add(name, new MutablePalette(p));
+				mutablePalettes.Add(name, new MutablePalette(p));
 			else
 				CopyPaletteToBuffer(index, p);
 		}

+		[System.Diagnostics.CodeAnalysis.SuppressMessage(
+			"Performance", "CA1854:Prefer the 'IDictionary.TryGetValue(TKey, out TValue)' method",
+			Justification = "False positive - indexer is a set not a get.")]
 		public void ReplacePalette(string name, IPalette p)
 		{
-			if (modifiablePalettes.ContainsKey(name))
-				CopyPaletteToBuffer(indices[name], modifiablePalettes[name] = new MutablePalette(p));
+			if (mutablePalettes.ContainsKey(name))
+				CopyPaletteToBuffer(indices[name], mutablePalettes[name] = new MutablePalette(p));
 			else if (palettes.ContainsKey(name))
 				CopyPaletteToBuffer(indices[name], palettes[name] = new ImmutablePalette(p));
 			else
-				throw new InvalidOperationException("Palette `{0}` does not exist".F(name));
+				throw new InvalidOperationException($"Palette `{name}` does not exist");
 			CopyBufferToTexture();
 		}

+		public void SetColorShift(string name, float hueOffset, float satOffset, float valueMultiplier, float minHue, float maxHue)
+		{
+			var index = GetPaletteIndex(name);
+			colorShiftBuffer[8 * index + 0] = minHue;
+			colorShiftBuffer[8 * index + 1] = maxHue;
+			colorShiftBuffer[8 * index + 4] = hueOffset;
+			colorShiftBuffer[8 * index + 5] = satOffset;
+			colorShiftBuffer[8 * index + 6] = valueMultiplier;
+		}
+
+		public bool HasColorShift(string name)
+		{
+			var index = GetPaletteIndex(name);
+			return colorShiftBuffer[8 * index] != 0 || colorShiftBuffer[8 * index + 1] != 0;
+		}
+
 		public void Initialize()
 		{
 			CopyModifiablePalettesToBuffer();
@@ -97,26 +122,27 @@ namespace OpenRA.Graphics

 		void CopyModifiablePalettesToBuffer()
 		{
-			foreach (var kvp in modifiablePalettes)
+			foreach (var kvp in mutablePalettes)
 				CopyPaletteToBuffer(indices[kvp.Key], kvp.Value);
 		}

 		void CopyBufferToTexture()
 		{
 			Texture.SetData(buffer, Palette.Size, Height);
+			ColorShifts.SetFloatData(colorShiftBuffer, 2, Height);
 		}

 		public void ApplyModifiers(IEnumerable<IPaletteModifier> paletteMods)
 		{
 			foreach (var mod in paletteMods)
-				mod.AdjustPalette(readOnlyModifiablePalettes);
+				mod.AdjustPalette(mutablePalettes);

 			// Update our texture with the changes.
 			CopyModifiablePalettesToBuffer();
 			CopyBufferToTexture();

 			// Reset modified palettes back to their original colors, ready for next time.
-			foreach (var kvp in modifiablePalettes)
+			foreach (var kvp in mutablePalettes)
 			{
 				var originalPalette = palettes[kvp.Key];
 				var modifiedPalette = kvp.Value;
@@ -127,6 +153,7 @@ namespace OpenRA.Graphics
 		public void Dispose()
 		{
 			Texture.Dispose();
+			ColorShifts.Dispose();
 		}
 	}
 }
--- a/OpenRA.Game/Graphics/Model.cs
+++ b/OpenRA.Game/Graphics/Model.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -10,6 +10,7 @@
 #endregion

 using System;
+using System.Collections.Generic;
 using OpenRA.FileSystem;
 using OpenRA.Primitives;

@@ -25,11 +26,11 @@ namespace OpenRA.Graphics
 		float[] Bounds(uint frame);
 		ModelRenderData RenderData(uint section);

-		/// <summary>Returns the smallest rectangle that covers all rotations of all frames in a model</summary>
+		/// <summary>Returns the smallest rectangle that covers all rotations of all frames in a model.</summary>
 		Rectangle AggregateBounds { get; }
 	}

-	public struct ModelRenderData
+	public readonly struct ModelRenderData
 	{
 		public readonly int Start;
 		public readonly int Count;
@@ -45,6 +46,7 @@ namespace OpenRA.Graphics

 	public interface IModelCache : IDisposable
 	{
+		IModel GetModel(string model);
 		IModel GetModelSequence(string model, string sequence);
 		bool HasModelSequence(string model, string sequence);
 		IVertexBuffer<Vertex> VertexBuffer { get; }
@@ -60,12 +62,17 @@ namespace OpenRA.Graphics
 	{
 		public Action<string> OnMissingModelError { get; set; }

-		class PlaceholderModelCache : IModelCache
+		sealed class PlaceholderModelCache : IModelCache
 		{
-			public IVertexBuffer<Vertex> VertexBuffer { get { throw new NotImplementedException(); } }
+			public IVertexBuffer<Vertex> VertexBuffer => throw new NotImplementedException();

 			public void Dispose() { }

+			public IModel GetModel(string model)
+			{
+				throw new NotImplementedException();
+			}
+
 			public IModel GetModelSequence(string model, string sequence)
 			{
 				throw new NotImplementedException();
--- a/OpenRA.Game/Graphics/ModelAnimation.cs
+++ b/OpenRA.Game/Graphics/ModelAnimation.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -14,7 +14,7 @@ using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
-	public struct ModelAnimation
+	public readonly struct ModelAnimation
 	{
 		public readonly IModel Model;
 		public readonly Func<WVec> OffsetFunc;
@@ -46,12 +46,6 @@ namespace OpenRA.Graphics
 				xy.Y + (int)(r.Bottom * scale));
 		}

-		public bool IsVisible
-		{
-			get
-			{
-				return DisableFunc == null || !DisableFunc();
-			}
-		}
+		public bool IsVisible => DisableFunc == null || !DisableFunc();
 	}
 }
--- a/OpenRA.Game/Graphics/ModelRenderer.cs
+++ b/OpenRA.Game/Graphics/ModelRenderer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -37,18 +37,19 @@ namespace OpenRA.Graphics
 		// Static constants
 		static readonly float[] ShadowDiffuse = new float[] { 0, 0, 0 };
 		static readonly float[] ShadowAmbient = new float[] { 1, 1, 1 };
-		static readonly float2 SpritePadding = new float2(2, 2);
+		static readonly float2 SpritePadding = new(2, 2);
 		static readonly float[] ZeroVector = new float[] { 0, 0, 0, 1 };
 		static readonly float[] ZVector = new float[] { 0, 0, 1, 1 };
 		static readonly float[] FlipMtx = Util.ScaleMatrix(1, -1, 1);
 		static readonly float[] ShadowScaleFlipMtx = Util.ScaleMatrix(2, -2, 2);
+		static readonly float[] GroundNormal = { 0, 0, 1, 1 };

 		readonly Renderer renderer;
 		readonly IShader shader;

-		readonly Dictionary<Sheet, IFrameBuffer> mappedBuffers = new Dictionary<Sheet, IFrameBuffer>();
-		readonly Stack<KeyValuePair<Sheet, IFrameBuffer>> unmappedBuffers = new Stack<KeyValuePair<Sheet, IFrameBuffer>>();
-		readonly List<(Sheet Sheet, Action Func)> doRender = new List<(Sheet, Action)>();
+		readonly Dictionary<Sheet, IFrameBuffer> mappedBuffers = new();
+		readonly Stack<KeyValuePair<Sheet, IFrameBuffer>> unmappedBuffers = new();
+		readonly List<(Sheet Sheet, Action Func)> doRender = new();

 		SheetBuilder sheetBuilderForFrame;
 		bool isInFrame;
@@ -64,7 +65,7 @@ namespace OpenRA.Graphics
 			shader.SetTexture("Palette", palette);
 		}

-		public void SetViewportParams(Size screen, int2 scroll)
+		public void SetViewportParams()
 		{
 			var a = 2f / renderer.SheetSize;
 			var view = new[]
@@ -80,7 +81,7 @@ namespace OpenRA.Graphics

 		public ModelRenderProxy RenderAsync(
 			WorldRenderer wr, IEnumerable<ModelAnimation> models, in WRot camera, float scale,
-			float[] groundNormal, in WRot lightSource, float[] lightAmbientColor, float[] lightDiffuseColor,
+			in WRot groundOrientation, in WRot lightSource, float[] lightAmbientColor, float[] lightDiffuseColor,
 			PaletteReference color, PaletteReference normals, PaletteReference shadowPalette)
 		{
 			if (!isInFrame)
@@ -92,7 +93,10 @@ namespace OpenRA.Graphics
 			// Correct for bogus light source definition
 			var lightYaw = Util.MakeFloatMatrix(new WRot(WAngle.Zero, WAngle.Zero, -lightSource.Yaw).AsMatrix());
 			var lightPitch = Util.MakeFloatMatrix(new WRot(WAngle.Zero, -lightSource.Pitch, WAngle.Zero).AsMatrix());
-			var shadowTransform = Util.MatrixMultiply(lightPitch, lightYaw);
+			var ground = Util.MakeFloatMatrix(groundOrientation.AsMatrix());
+			var shadowTransform = Util.MatrixMultiply(Util.MatrixMultiply(lightPitch, lightYaw), Util.MatrixInverse(ground));
+
+			var groundNormal = Util.MatrixVectorMultiply(ground, GroundNormal);

 			var invShadowTransform = Util.MatrixInverse(shadowTransform);
 			var cameraTransform = Util.MakeFloatMatrix(camera.AsMatrix());
@@ -163,8 +167,7 @@ namespace OpenRA.Graphics
 			CalculateSpriteGeometry(tl, br, 1, out var spriteSize, out var spriteOffset);
 			CalculateSpriteGeometry(stl, sbr, 2, out var shadowSpriteSize, out var shadowSpriteOffset);

-			if (sheetBuilderForFrame == null)
-				sheetBuilderForFrame = new SheetBuilder(SheetType.BGRA, AllocateSheet);
+			sheetBuilderForFrame ??= new SheetBuilder(SheetType.BGRA, AllocateSheet);

 			var sprite = sheetBuilderForFrame.Allocate(spriteSize, 0, spriteOffset);
 			var shadowSprite = sheetBuilderForFrame.Allocate(shadowSpriteSize, 0, shadowSpriteOffset);
@@ -205,7 +208,7 @@ namespace OpenRA.Graphics
 						var t = m.Model.TransformationMatrix(i, frame);
 						var it = Util.MatrixInverse(t);
 						if (it == null)
-							throw new InvalidOperationException("Failed to invert the transformed matrix of frame {0} during RenderAsync.".F(i));
+							throw new InvalidOperationException($"Failed to invert the transformed matrix of frame {i} during RenderAsync.");

 						// Transform light vector from shadow -> world -> limb coords
 						var lightDirection = ExtractRotationVector(Util.MatrixMultiply(it, lightTransform));
@@ -299,7 +302,7 @@ namespace OpenRA.Graphics
 			return fbo;
 		}

-		void DisableFrameBuffer(IFrameBuffer fbo)
+		static void DisableFrameBuffer(IFrameBuffer fbo)
 		{
 			Game.Renderer.Flush();
 			Game.Renderer.Context.DisableDepthBuffer();
--- a/OpenRA.Game/Graphics/Palette.cs
+++ b/OpenRA.Game/Graphics/Palette.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -40,11 +40,12 @@ namespace OpenRA.Graphics
 			return new ReadOnlyPalette(palette);
 		}

-		class ReadOnlyPalette : IPalette
+		sealed class ReadOnlyPalette : IPalette
 		{
-			IPalette palette;
+			readonly IPalette palette;
 			public ReadOnlyPalette(IPalette palette) { this.palette = palette; }
-			public uint this[int index] { get { return palette[index]; } }
+			public uint this[int index] => palette[index];
+
 			public void CopyToArray(Array destination, int destinationOffset)
 			{
 				palette.CopyToArray(destination, destinationOffset);
@@ -56,28 +57,25 @@ namespace OpenRA.Graphics
 	{
 		readonly uint[] colors = new uint[Palette.Size];

-		public uint this[int index]
-		{
-			get { return colors[index]; }
-		}
+		public uint this[int index] => colors[index];

 		public void CopyToArray(Array destination, int destinationOffset)
 		{
 			Buffer.BlockCopy(colors, 0, destination, destinationOffset * 4, Palette.Size * 4);
 		}

-		public ImmutablePalette(string filename, int[] remap)
+		public ImmutablePalette(string filename, int[] remapTransparent, int[] remap)
 		{
 			using (var s = File.OpenRead(filename))
-				LoadFromStream(s, remap);
+				LoadFromStream(s, remapTransparent, remap);
 		}

-		public ImmutablePalette(Stream s, int[] remapShadow)
+		public ImmutablePalette(Stream s, int[] remapTransparent, int[] remapShadow)
 		{
-			LoadFromStream(s, remapShadow);
+			LoadFromStream(s, remapTransparent, remapShadow);
 		}

-		void LoadFromStream(Stream s, int[] remapShadow)
+		void LoadFromStream(Stream s, int[] remapTransparent, int[] remapShadow)
 		{
 			using (var reader = new BinaryReader(s))
 				for (var i = 0; i < Palette.Size; i++)
@@ -94,7 +92,9 @@ namespace OpenRA.Graphics
 					colors[i] = (uint)((255 << 24) | (r << 16) | (g << 8) | b);
 				}

-			colors[0] = 0; // Convert black background to transparency.
+			foreach (var i in remapTransparent)
+				colors[i] = 0;
+
 			foreach (var i in remapShadow)
 				colors[i] = 140u << 24;
 		}
@@ -108,7 +108,7 @@ namespace OpenRA.Graphics

 		public ImmutablePalette(IPalette p)
 		{
-			for (int i = 0; i < Palette.Size; i++)
+			for (var i = 0; i < Palette.Size; i++)
 				colors[i] = p[i];
 		}

@@ -126,8 +126,8 @@ namespace OpenRA.Graphics

 		public uint this[int index]
 		{
-			get { return colors[index]; }
-			set { colors[index] = value; }
+			get => colors[index];
+			set => colors[index] = value;
 		}

 		public void CopyToArray(Array destination, int destinationOffset)
--- a/OpenRA.Game/Graphics/PaletteReference.cs
+++ b/OpenRA.Game/Graphics/PaletteReference.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -18,8 +18,8 @@ namespace OpenRA.Graphics

 		public readonly string Name;
 		public IPalette Palette { get; internal set; }
-		public float TextureIndex { get { return index / hardwarePalette.Height; } }
-		public float TextureMidIndex { get { return (index + 0.5f) / hardwarePalette.Height; } }
+		public float TextureIndex => index / hardwarePalette.Height;
+		public float TextureMidIndex => (index + 0.5f) / hardwarePalette.Height;

 		public PaletteReference(string name, int index, IPalette palette, HardwarePalette hardwarePalette)
 		{
@@ -28,5 +28,7 @@ namespace OpenRA.Graphics
 			this.index = index;
 			this.hardwarePalette = hardwarePalette;
 		}
+
+		public bool HasColorShift => hardwarePalette.HasColorShift(Name);
 	}
 }
--- a/OpenRA.Game/Graphics/PlatformInterfaces.cs
+++ b/OpenRA.Game/Graphics/PlatformInterfaces.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -59,6 +59,7 @@ namespace OpenRA
 		int DisplayCount { get; }
 		int CurrentDisplay { get; }
 		bool HasInputFocus { get; }
+		bool IsSuspended { get; }

 		event Action<float, float, float, float> OnWindowScaleChanged;

@@ -71,6 +72,7 @@ namespace OpenRA

 		IHardwareCursor CreateHardwareCursor(string name, Size size, byte[] data, int2 hotspot, bool pixelDouble);
 		void SetHardwareCursor(IHardwareCursor cursor);
+		void SetWindowTitle(string title);
 		void SetRelativeMouseMode(bool mode);
 		void SetScaleModifier(float scale);

@@ -82,6 +84,7 @@ namespace OpenRA
 	public interface IGraphicsContext : IDisposable
 	{
 		IVertexBuffer<Vertex> CreateVertexBuffer(int size);
+		Vertex[] CreateVertices(int size);
 		ITexture CreateTexture();
 		IFrameBuffer CreateFrameBuffer(Size s);
 		IFrameBuffer CreateFrameBuffer(Size s, Color clearColor);
@@ -103,6 +106,11 @@ namespace OpenRA
 	{
 		void Bind();
 		void SetData(T[] vertices, int length);
+
+		/// <summary>
+		/// Upon return `vertices` may reference another array object of at least the same size - containing random values.
+		/// </summary>
+		void SetData(ref T[] vertices, int length);
 		void SetData(T[] vertices, int offset, int start, int length);
 	}

@@ -122,8 +130,8 @@ namespace OpenRA

 	public interface ITexture : IDisposable
 	{
-		void SetData(uint[,] colors);
 		void SetData(byte[] colors, int width, int height);
+		void SetFloatData(float[] data, int width, int height);
 		byte[] GetData();
 		Size Size { get; }
 		TextureScaleFilter ScaleFilter { get; set; }
@@ -145,7 +153,7 @@ namespace OpenRA
 		TriangleList,
 	}

-	public struct Range<T>
+	public readonly struct Range<T>
 	{
 		public readonly T Start, End;
 		public Range(T start, T end) { Start = start; End = end; }
--- a/OpenRA.Game/Graphics/PlayerColorRemap.cs
+++ b/OpenRA.Game/Graphics/PlayerColorRemap.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -10,7 +10,6 @@
 #endregion

 using System;
-using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Primitives;

@@ -18,43 +17,37 @@ namespace OpenRA.Graphics
 {
 	public class PlayerColorRemap : IPaletteRemap
 	{
-		Dictionary<int, Color> remapColors;
+		readonly int[] remapIndices;
+		readonly float hue;
+		readonly float saturation;
+		readonly float value;

-		public static int GetRemapIndex(int[] ramp, int i)
+		public PlayerColorRemap(int[] remapIndices, Color color)
 		{
-			return ramp[i];
-		}
+			this.remapIndices = remapIndices;

-		public PlayerColorRemap(int[] ramp, Color c, float rampFraction)
-		{
-			var h = c.GetHue() / 360.0f;
-			var s = c.GetSaturation();
-			var l = c.GetBrightness();
-
-			// Increase luminosity if required to represent the full ramp
-			var rampRange = (byte)((1 - rampFraction) * l);
-			var c1 = Color.FromAhsl(h, s, Math.Max(rampRange, l));
-			var c2 = Color.FromAhsl(h, s, (byte)Math.Max(0, l - rampRange));
-			var baseIndex = ramp[0];
-			var remapRamp = ramp.Select(r => r - ramp[0]);
-			var rampMaxIndex = ramp.Length - 1;
-
-			// reversed remapping
-			if (ramp[0] > ramp[rampMaxIndex])
-			{
-				baseIndex = ramp[rampMaxIndex];
-				for (var i = rampMaxIndex; i > 0; i--)
-					remapRamp = ramp.Select(r => r - ramp[rampMaxIndex]);
-			}
-
-			remapColors = remapRamp.Select((x, i) => (baseIndex + i, Exts.ColorLerp(x / (float)ramp.Length, c1, c2)))
-				.ToDictionary(u => u.Item1, u => u.Item2);
+			var (r, g, b) = color.ToLinear();
+			(hue, saturation, value) = Color.RgbToHsv(r, g, b);
 		}

 		public Color GetRemappedColor(Color original, int index)
 		{
-			return remapColors.TryGetValue(index, out var c)
-				? c : original;
+			if (!remapIndices.Contains(index))
+				return original;
+
+			// Color remapping is applied in a linear color space, so start
+			// by undoing the pre-multiplied alpha and gamma corrections
+			var (r, g, b) = original.ToLinear();
+
+			// Calculate the brightness (i.e HSV value) of the original colour
+			// This inlines the single line of Color.RgbToHsv() that we need
+			var value = Math.Max(Math.Max(r, g), b);
+
+			// Construct the new RGB color
+			(r, g, b) = Color.HsvToRgb(hue, saturation, value * this.value);
+
+			// Convert linear back to SRGB and pre-multiply by the alpha
+			return Color.FromLinear(original.A, r, g, b);
 		}
 	}
 }
--- a/OpenRA.Game/Graphics/Renderable.cs
+++ b/OpenRA.Game/Graphics/Renderable.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -9,6 +9,7 @@
 */
 #endregion

+using System;
 using OpenRA.Primitives;

 namespace OpenRA.Graphics
@@ -16,21 +17,38 @@ namespace OpenRA.Graphics
 	public interface IRenderable
 	{
 		WPos Pos { get; }
-		PaletteReference Palette { get; }
 		int ZOffset { get; }
 		bool IsDecoration { get; }

-		IRenderable WithPalette(PaletteReference newPalette);
 		IRenderable WithZOffset(int newOffset);
-		IRenderable OffsetBy(WVec offset);
+		IRenderable OffsetBy(in WVec offset);
 		IRenderable AsDecoration();

 		IFinalizedRenderable PrepareRender(WorldRenderer wr);
 	}

-	public interface ITintableRenderable
+	public interface IPalettedRenderable : IRenderable
 	{
-		IRenderable WithTint(in float3 newTint);
+		PaletteReference Palette { get; }
+		IPalettedRenderable WithPalette(PaletteReference newPalette);
+	}
+
+	[Flags]
+	public enum TintModifiers
+	{
+		None = 0,
+		IgnoreWorldTint = 1,
+		ReplaceColor = 2
+	}
+
+	public interface IModifyableRenderable : IRenderable
+	{
+		float Alpha { get; }
+		float3 Tint { get; }
+		TintModifiers TintModifiers { get; }
+
+		IModifyableRenderable WithAlpha(float newAlpha);
+		IModifyableRenderable WithTint(in float3 newTint, TintModifiers newTintModifiers);
 	}

 	public interface IFinalizedRenderable
--- a/OpenRA.Game/Graphics/RgbaColorRenderer.cs
+++ b/OpenRA.Game/Graphics/RgbaColorRenderer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -18,7 +18,7 @@ namespace OpenRA.Graphics
 {
 	public class RgbaColorRenderer
 	{
-		static readonly float3 Offset = new float3(0.5f, 0.5f, 0f);
+		static readonly float3 Offset = new(0.5f, 0.5f, 0f);

 		readonly SpriteRenderer parent;
 		readonly Vertex[] vertices = new Vertex[6];
@@ -28,7 +28,7 @@ namespace OpenRA.Graphics
 			this.parent = parent;
 		}

-		public void DrawLine(in float3 start, in float3 end, float width, Color startColor, Color endColor)
+		public void DrawLine(in float3 start, in float3 end, float width, Color startColor, Color endColor, BlendMode blendMode = BlendMode.Alpha)
 		{
 			var delta = (end - start) / (end - start).XY.Length;
 			var corner = width / 2 * new float3(-delta.Y, delta.X, delta.Z);
@@ -52,10 +52,10 @@ namespace OpenRA.Graphics
 			vertices[4] = new Vertex(end - corner + Offset, er, eg, eb, ea, 0, 0);
 			vertices[5] = new Vertex(start - corner + Offset, sr, sg, sb, sa, 0, 0);

-			parent.DrawRGBAVertices(vertices);
+			parent.DrawRGBAVertices(vertices, blendMode);
 		}

-		public void DrawLine(in float3 start, in float3 end, float width, Color color)
+		public void DrawLine(in float3 start, in float3 end, float width, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			var delta = (end - start) / (end - start).XY.Length;
 			var corner = width / 2 * new float2(-delta.Y, delta.X);
@@ -72,15 +72,15 @@ namespace OpenRA.Graphics
 			vertices[3] = new Vertex(end + corner + Offset, r, g, b, a, 0, 0);
 			vertices[4] = new Vertex(end - corner + Offset, r, g, b, a, 0, 0);
 			vertices[5] = new Vertex(start - corner + Offset, r, g, b, a, 0, 0);
-			parent.DrawRGBAVertices(vertices);
+			parent.DrawRGBAVertices(vertices, blendMode);
 		}

 		/// <summary>
 		/// Calculate the 2D intersection of two lines.
 		/// Will behave badly if the lines are parallel.
-		/// Z position is the average of a and b (ignores actual intersection point if it exists)
+		/// Z position is the average of a and b (ignores actual intersection point if it exists).
 		/// </summary>
-		float3 IntersectionOf(in float3 a, in float3 da, in float3 b, in float3 db)
+		static float3 IntersectionOf(in float3 a, in float3 da, in float3 b, in float3 db)
 		{
 			var crossA = a.X * (a.Y + da.Y) - a.Y * (a.X + da.X);
 			var crossB = b.X * (b.Y + db.Y) - b.Y * (b.X + db.X);
@@ -90,7 +90,7 @@ namespace OpenRA.Graphics
 			return new float3(x / d, y / d, 0.5f * (a.Z + b.Z));
 		}

-		void DrawDisconnectedLine(IEnumerable<float3> points, float width, Color color)
+		void DrawDisconnectedLine(IEnumerable<float3> points, float width, Color color, BlendMode blendMode)
 		{
 			using (var e = points.GetEnumerator())
 			{
@@ -101,13 +101,13 @@ namespace OpenRA.Graphics
 				while (e.MoveNext())
 				{
 					var point = e.Current;
-					DrawLine(lastPoint, point, width, color);
+					DrawLine(lastPoint, point, width, color, blendMode);
 					lastPoint = point;
 				}
 			}
 		}

-		void DrawConnectedLine(float3[] points, float width, Color color, bool closed)
+		void DrawConnectedLine(float3[] points, float width, Color color, bool closed, BlendMode blendMode)
 		{
 			// Not a line
 			if (points.Length < 2)
@@ -116,7 +116,7 @@ namespace OpenRA.Graphics
 			// Single segment
 			if (points.Length == 2)
 			{
-				DrawLine(points[0], points[1], width, color);
+				DrawLine(points[0], points[1], width, color, blendMode);
 				return;
 			}

@@ -138,7 +138,7 @@ namespace OpenRA.Graphics
 			// Segment is part of closed loop
 			if (closed)
 			{
-				var prev = points[points.Length - 1];
+				var prev = points[^1];
 				var prevDir = (start - prev) / (start - prev).XY.Length;
 				var prevCorner = width / 2 * new float3(-prevDir.Y, prevDir.X, prevDir.Z);
 				ca = IntersectionOf(start - prevCorner, prevDir, start - corner, dir);
@@ -163,7 +163,7 @@ namespace OpenRA.Graphics
 				vertices[3] = new Vertex(cc + Offset, r, g, b, a, 0, 0);
 				vertices[4] = new Vertex(cd + Offset, r, g, b, a, 0, 0);
 				vertices[5] = new Vertex(ca + Offset, r, g, b, a, 0, 0);
-				parent.DrawRGBAVertices(vertices);
+				parent.DrawRGBAVertices(vertices, blendMode);

 				// Advance line segment
 				end = next;
@@ -175,32 +175,32 @@ namespace OpenRA.Graphics
 			}
 		}

-		public void DrawLine(IEnumerable<float3> points, float width, Color color, bool connectSegments = false)
+		public void DrawLine(IEnumerable<float3> points, float width, Color color, bool connectSegments = false, BlendMode blendMode = BlendMode.Alpha)
 		{
 			if (!connectSegments)
-				DrawDisconnectedLine(points, width, color);
+				DrawDisconnectedLine(points, width, color, blendMode);
 			else
-				DrawConnectedLine(points as float3[] ?? points.ToArray(), width, color, false);
+				DrawConnectedLine(points as float3[] ?? points.ToArray(), width, color, false, blendMode);
 		}

-		public void DrawPolygon(float3[] vertices, float width, Color color)
+		public void DrawPolygon(float3[] vertices, float width, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
-			DrawConnectedLine(vertices, width, color, true);
+			DrawConnectedLine(vertices, width, color, true, blendMode);
 		}

-		public void DrawPolygon(float2[] vertices, float width, Color color)
+		public void DrawPolygon(float2[] vertices, float width, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
-			DrawConnectedLine(vertices.Select(v => new float3(v, 0)).ToArray(), width, color, true);
+			DrawConnectedLine(vertices.Select(v => new float3(v, 0)).ToArray(), width, color, true, blendMode);
 		}

-		public void DrawRect(in float3 tl, in float3 br, float width, Color color)
+		public void DrawRect(in float3 tl, in float3 br, float width, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			var tr = new float3(br.X, tl.Y, tl.Z);
 			var bl = new float3(tl.X, br.Y, br.Z);
-			DrawPolygon(new[] { tl, tr, br, bl }, width, color);
+			DrawPolygon(new[] { tl, tr, br, bl }, width, color, blendMode);
 		}

-		public void FillTriangle(in float3 a, in float3 b, in float3 c, Color color)
+		public void FillTriangle(in float3 a, in float3 b, in float3 c, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			color = Util.PremultiplyAlpha(color);
 			var cr = color.R / 255.0f;
@@ -211,17 +211,17 @@ namespace OpenRA.Graphics
 			vertices[0] = new Vertex(a + Offset, cr, cg, cb, ca, 0, 0);
 			vertices[1] = new Vertex(b + Offset, cr, cg, cb, ca, 0, 0);
 			vertices[2] = new Vertex(c + Offset, cr, cg, cb, ca, 0, 0);
-			parent.DrawRGBAVertices(vertices);
+			parent.DrawRGBAVertices(vertices, blendMode);
 		}

-		public void FillRect(in float3 tl, in float3 br, Color color)
+		public void FillRect(in float3 tl, in float3 br, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			var tr = new float3(br.X, tl.Y, tl.Z);
 			var bl = new float3(tl.X, br.Y, br.Z);
-			FillRect(tl, tr, br, bl, color);
+			FillRect(tl, tr, br, bl, color, blendMode);
 		}

-		public void FillRect(in float3 a, in float3 b, in float3 c, in float3 d, Color color)
+		public void FillRect(in float3 a, in float3 b, in float3 c, in float3 d, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			color = Util.PremultiplyAlpha(color);
 			var cr = color.R / 255.0f;
@@ -235,10 +235,10 @@ namespace OpenRA.Graphics
 			vertices[3] = new Vertex(c + Offset, cr, cg, cb, ca, 0, 0);
 			vertices[4] = new Vertex(d + Offset, cr, cg, cb, ca, 0, 0);
 			vertices[5] = new Vertex(a + Offset, cr, cg, cb, ca, 0, 0);
-			parent.DrawRGBAVertices(vertices);
+			parent.DrawRGBAVertices(vertices, blendMode);
 		}

-		public void FillRect(in float3 a, in float3 b, in float3 c, in float3 d, Color topLeftColor, Color topRightColor, Color bottomRightColor, Color bottomLeftColor)
+		public void FillRect(in float3 a, in float3 b, in float3 c, in float3 d, Color topLeftColor, Color topRightColor, Color bottomRightColor, Color bottomLeftColor, BlendMode blendMode = BlendMode.Alpha)
 		{
 			vertices[0] = VertexWithColor(a + Offset, topLeftColor);
 			vertices[1] = VertexWithColor(b + Offset, topRightColor);
@@ -247,7 +247,7 @@ namespace OpenRA.Graphics
 			vertices[4] = VertexWithColor(d + Offset, bottomLeftColor);
 			vertices[5] = VertexWithColor(a + Offset, topLeftColor);

-			parent.DrawRGBAVertices(vertices);
+			parent.DrawRGBAVertices(vertices, blendMode);
 		}

 		static Vertex VertexWithColor(in float3 xyz, Color color)
@@ -261,7 +261,7 @@ namespace OpenRA.Graphics
 			return new Vertex(xyz, cr, cg, cb, ca, 0, 0);
 		}

-		public void FillEllipse(in float3 tl, in float3 br, Color color, int vertices = 32)
+		public void FillEllipse(in float3 tl, in float3 br, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			// TODO: Create an ellipse polygon instead
 			var a = (br.X - tl.X) / 2;
@@ -272,7 +272,7 @@ namespace OpenRA.Graphics
 			{
 				var z = float2.Lerp(tl.Z, br.Z, (y - tl.Y) / (br.Y - tl.Y));
 				var dx = a * (float)Math.Sqrt(1 - (y - yc) * (y - yc) / b / b);
-				DrawLine(new float3(xc - dx, y, z), new float3(xc + dx, y, z), 1, color);
+				DrawLine(new float3(xc - dx, y, z), new float3(xc + dx, y, z), 1, color, blendMode);
 			}
 		}
 	}
--- a/OpenRA.Game/Graphics/RgbaSpriteRenderer.cs
+++ b/OpenRA.Game/Graphics/RgbaSpriteRenderer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -22,44 +22,36 @@ namespace OpenRA.Graphics
 			this.parent = parent;
 		}

-		public void DrawSprite(Sprite s, in float3 location, in float3 size)
+		public void DrawSprite(Sprite s, in float3 location, in float3 scale, float rotation = 0f)
 		{
 			if (s.Channel != TextureChannel.RGBA)
 				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");

-			parent.DrawSprite(s, location, 0, size);
+			parent.DrawSprite(s, 0, location, scale, rotation);
 		}

-		public void DrawSprite(Sprite s, in float3 location)
+		public void DrawSprite(Sprite s, in float3 location, float scale = 1f, float rotation = 0f)
 		{
 			if (s.Channel != TextureChannel.RGBA)
 				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");

-			parent.DrawSprite(s, location, 0, s.Size);
+			parent.DrawSprite(s, 0, location, scale, rotation);
 		}

-		public void DrawSprite(Sprite s, in float3 a, in float3 b, in float3 c, in float3 d)
+		public void DrawSprite(Sprite s, in float3 location, float scale, in float3 tint, float alpha, float rotation = 0f)
 		{
 			if (s.Channel != TextureChannel.RGBA)
 				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");

-			parent.DrawSprite(s, a, b, c, d);
+			parent.DrawSprite(s, 0, location, scale, tint, alpha, rotation);
 		}

-		public void DrawSpriteWithTint(Sprite s, in float3 location, in float3 size, in float3 tint)
+		public void DrawSprite(Sprite s, in float3 a, in float3 b, in float3 c, in float3 d, in float3 tint, float alpha)
 		{
 			if (s.Channel != TextureChannel.RGBA)
 				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");

-			parent.DrawSpriteWithTint(s, location, 0, size, tint);
-		}
-
-		public void DrawSpriteWithTint(Sprite s, in float3 a, in float3 b, in float3 c, in float3 d, in float3 tint)
-		{
-			if (s.Channel != TextureChannel.RGBA)
-				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");
-
-			parent.DrawSpriteWithTint(s, a, b, c, d, tint);
+			parent.DrawSprite(s, 0, a, b, c, d, tint, alpha);
 		}
 	}
 }
--- a/OpenRA.Game/Graphics/SequenceProvider.cs
+++ b/OpenRA.Game/Graphics/SequenceProvider.cs
@@ -1,148 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-using System;
-using System.Collections.Generic;
-using OpenRA.FileSystem;
-using OpenRA.Primitives;
-
-namespace OpenRA.Graphics
-{
-	using Sequences = IReadOnlyDictionary<string, Lazy<IReadOnlyDictionary<string, ISpriteSequence>>>;
-	using UnitSequences = Lazy<IReadOnlyDictionary<string, ISpriteSequence>>;
-
-	public interface ISpriteSequence
-	{
-		string Name { get; }
-		int Start { get; }
-		int Length { get; }
-		int Stride { get; }
-		int Facings { get; }
-		int Tick { get; }
-		int ZOffset { get; }
-		int ShadowStart { get; }
-		int ShadowZOffset { get; }
-		int[] Frames { get; }
-		Rectangle Bounds { get; }
-		bool IgnoreWorldTint { get; }
-
-		Sprite GetSprite(int frame);
-		Sprite GetSprite(int frame, WAngle facing);
-		Sprite GetShadow(int frame, WAngle facing);
-	}
-
-	public interface ISpriteSequenceLoader
-	{
-		IReadOnlyDictionary<string, ISpriteSequence> ParseSequences(ModData modData, string tileSet, SpriteCache cache, MiniYamlNode node);
-	}
-
-	public class SequenceProvider : IDisposable
-	{
-		readonly ModData modData;
-		readonly string tileSet;
-		readonly Lazy<Sequences> sequences;
-		readonly Lazy<SpriteCache> spriteCache;
-		public SpriteCache SpriteCache { get { return spriteCache.Value; } }
-
-		readonly Dictionary<string, UnitSequences> sequenceCache = new Dictionary<string, UnitSequences>();
-
-		public SequenceProvider(IReadOnlyFileSystem fileSystem, ModData modData, string tileSet, MiniYaml additionalSequences)
-		{
-			this.modData = modData;
-			this.tileSet = tileSet;
-			sequences = Exts.Lazy(() =>
-			{
-				using (new Support.PerfTimer("LoadSequences"))
-					return Load(fileSystem, additionalSequences);
-			});
-
-			spriteCache = Exts.Lazy(() => new SpriteCache(fileSystem, modData.SpriteLoaders));
-		}
-
-		public ISpriteSequence GetSequence(string unitName, string sequenceName)
-		{
-			if (!sequences.Value.TryGetValue(unitName, out var unitSeq))
-				throw new InvalidOperationException("Unit `{0}` does not have any sequences defined.".F(unitName));
-
-			if (!unitSeq.Value.TryGetValue(sequenceName, out var seq))
-				throw new InvalidOperationException("Unit `{0}` does not have a sequence named `{1}`".F(unitName, sequenceName));
-
-			return seq;
-		}
-
-		public IEnumerable<string> Images { get { return sequences.Value.Keys; } }
-
-		public bool HasSequence(string unitName)
-		{
-			return sequences.Value.ContainsKey(unitName);
-		}
-
-		public bool HasSequence(string unitName, string sequenceName)
-		{
-			if (!sequences.Value.TryGetValue(unitName, out var unitSeq))
-				throw new InvalidOperationException("Unit `{0}` does not have any sequences defined.".F(unitName));
-
-			return unitSeq.Value.ContainsKey(sequenceName);
-		}
-
-		public IEnumerable<string> Sequences(string unitName)
-		{
-			if (!sequences.Value.TryGetValue(unitName, out var unitSeq))
-				throw new InvalidOperationException("Unit `{0}` does not have any sequences defined.".F(unitName));
-
-			return unitSeq.Value.Keys;
-		}
-
-		Sequences Load(IReadOnlyFileSystem fileSystem, MiniYaml additionalSequences)
-		{
-			var nodes = MiniYaml.Load(fileSystem, modData.Manifest.Sequences, additionalSequences);
-			var items = new Dictionary<string, UnitSequences>();
-			foreach (var node in nodes)
-			{
-				// Nodes starting with ^ are inheritable but never loaded directly
-				if (node.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal))
-					continue;
-
-				var key = node.Value.ToLines(node.Key).JoinWith("|");
-
-				if (sequenceCache.TryGetValue(key, out var t))
-					items.Add(node.Key, t);
-				else
-				{
-					t = Exts.Lazy(() => modData.SpriteSequenceLoader.ParseSequences(modData, tileSet, SpriteCache, node));
-					sequenceCache.Add(key, t);
-					items.Add(node.Key, t);
-				}
-			}
-
-			return new ReadOnlyDictionary<string, UnitSequences>(items);
-		}
-
-		public void Preload()
-		{
-			foreach (var sb in SpriteCache.SheetBuilders.Values)
-				sb.Current.CreateBuffer();
-
-			foreach (var unitSeq in sequences.Value.Values)
-				foreach (var seq in unitSeq.Value.Values) { }
-
-			foreach (var sb in SpriteCache.SheetBuilders.Values)
-				sb.Current.ReleaseBuffer();
-		}
-
-		public void Dispose()
-		{
-			if (spriteCache.IsValueCreated)
-				foreach (var sb in SpriteCache.SheetBuilders.Values)
-					sb.Dispose();
-		}
-	}
-}
--- a/OpenRA.Game/Graphics/SequenceSet.cs
+++ b/OpenRA.Game/Graphics/SequenceSet.cs
@@ -0,0 +1,119 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using OpenRA.FileSystem;
+using OpenRA.Primitives;
+
+namespace OpenRA.Graphics
+{
+	public interface ISpriteSequence
+	{
+		string Name { get; }
+		int Length { get; }
+		int Facings { get; }
+		int Tick { get; }
+		int ZOffset { get; }
+		int ShadowZOffset { get; }
+		Rectangle Bounds { get; }
+		bool IgnoreWorldTint { get; }
+		float Scale { get; }
+		void ResolveSprites(SpriteCache cache);
+		Sprite GetSprite(int frame);
+		Sprite GetSprite(int frame, WAngle facing);
+		(Sprite Sprite, WAngle Rotation) GetSpriteWithRotation(int frame, WAngle facing);
+		Sprite GetShadow(int frame, WAngle facing);
+		float GetAlpha(int frame);
+	}
+
+	public interface ISpriteSequenceLoader
+	{
+		int BgraSheetSize { get; }
+		int IndexedSheetSize { get; }
+		IReadOnlyDictionary<string, ISpriteSequence> ParseSequences(ModData modData, string tileSet, SpriteCache cache, MiniYamlNode node);
+	}
+
+	public sealed class SequenceSet : IDisposable
+	{
+		readonly ModData modData;
+		readonly string tileSet;
+		readonly IReadOnlyDictionary<string, IReadOnlyDictionary<string, ISpriteSequence>> images;
+		public SpriteCache SpriteCache { get; }
+
+		public SequenceSet(IReadOnlyFileSystem fileSystem, ModData modData, string tileSet, MiniYaml additionalSequences)
+		{
+			this.modData = modData;
+			this.tileSet = tileSet;
+			SpriteCache = new SpriteCache(fileSystem, modData.SpriteLoaders, modData.SpriteSequenceLoader.BgraSheetSize, modData.SpriteSequenceLoader.IndexedSheetSize);
+			using (new Support.PerfTimer("LoadSequences"))
+				images = Load(fileSystem, additionalSequences);
+		}
+
+		public ISpriteSequence GetSequence(string image, string sequence)
+		{
+			if (!images.TryGetValue(image, out var sequences))
+				throw new InvalidOperationException($"Image `{image}` does not have any sequences defined.");
+
+			if (!sequences.TryGetValue(sequence, out var seq))
+				throw new InvalidOperationException($"Image `{image}` does not have a sequence named `{sequence}`.");
+
+			return seq;
+		}
+
+		public IEnumerable<string> Images => images.Keys;
+
+		public bool HasSequence(string image, string sequence)
+		{
+			if (!images.TryGetValue(image, out var sequences))
+				throw new InvalidOperationException($"Image `{image}` does not have any sequences defined.");
+
+			return sequences.ContainsKey(sequence);
+		}
+
+		public IEnumerable<string> Sequences(string image)
+		{
+			if (!images.TryGetValue(image, out var sequences))
+				throw new InvalidOperationException($"Image `{image}` does not have any sequences defined.");
+
+			return sequences.Keys;
+		}
+
+		IReadOnlyDictionary<string, IReadOnlyDictionary<string, ISpriteSequence>> Load(IReadOnlyFileSystem fileSystem, MiniYaml additionalSequences)
+		{
+			var nodes = MiniYaml.Load(fileSystem, modData.Manifest.Sequences, additionalSequences);
+			var images = new Dictionary<string, IReadOnlyDictionary<string, ISpriteSequence>>();
+			foreach (var node in nodes)
+			{
+				// Nodes starting with ^ are inheritable but never loaded directly
+				if (node.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal))
+					continue;
+
+				images[node.Key] = modData.SpriteSequenceLoader.ParseSequences(modData, tileSet, SpriteCache, node);
+			}
+
+			return images;
+		}
+
+		public void LoadSprites()
+		{
+			SpriteCache.LoadReservations(modData);
+			foreach (var sequences in images.Values)
+				foreach (var sequence in sequences)
+					sequence.Value.ResolveSprites(SpriteCache);
+		}
+
+		public void Dispose()
+		{
+			SpriteCache.Dispose();
+		}
+	}
+}
--- a/OpenRA.Game/Graphics/Sheet.cs
+++ b/OpenRA.Game/Graphics/Sheet.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -32,7 +32,7 @@ namespace OpenRA.Graphics
 			return data;
 		}

-		public bool Buffered { get { return data != null || texture == null; } }
+		public bool Buffered => data != null || texture == null;

 		public Sheet(SheetType type, Size size)
 		{
@@ -79,21 +79,17 @@ namespace OpenRA.Graphics

 		public Png AsPng()
 		{
-			var data = GetData();
+			if (Type == SheetType.Indexed)
+				throw new InvalidOperationException("AsPng() cannot be called on Indexed sheets.");

-			// Convert BGRA to RGBA
-			for (var i = 0; i < Size.Width * Size.Height; i++)
-			{
-				var temp = data[i * 4];
-				data[i * 4] = data[i * 4 + 2];
-				data[i * 4 + 2] = temp;
-			}
-
-			return new Png(data, Size.Width, Size.Height);
+			return new Png(GetData(), SpriteFrameType.Bgra32, Size.Width, Size.Height);
 		}

 		public Png AsPng(TextureChannel channel, IPalette pal)
 		{
+			if (Type != SheetType.Indexed)
+				throw new InvalidOperationException("AsPng(TextureChannel, IPalette) can only be called on Indexed sheets.");
+
 			var d = GetData();
 			var plane = new byte[Size.Width * Size.Height];
 			var dataStride = 4 * Size.Width;
@@ -107,7 +103,7 @@ namespace OpenRA.Graphics
 			for (var i = 0; i < Palette.Size; i++)
 				palColors[i] = pal.GetColor(i);

-			return new Png(plane, Size.Width, Size.Height, palColors);
+			return new Png(plane, SpriteFrameType.Indexed8, Size.Width, Size.Height, palColors);
 		}

 		public void CreateBuffer()
--- a/OpenRA.Game/Graphics/SheetBuilder.cs
+++ b/OpenRA.Game/Graphics/SheetBuilder.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -34,15 +34,16 @@ namespace OpenRA.Graphics
 	public sealed class SheetBuilder : IDisposable
 	{
 		public readonly SheetType Type;
-		readonly List<Sheet> sheets = new List<Sheet>();
+		readonly List<Sheet> sheets = new();
 		readonly Func<Sheet> allocateSheet;
 		readonly int margin;
-
-		Sheet current;
-		TextureChannel channel;
 		int rowHeight = 0;
 		int2 p;

+		public Sheet Current { get; private set; }
+		public TextureChannel CurrentChannel { get; private set; }
+		public IEnumerable<Sheet> AllSheets => sheets;
+
 		public static Sheet AllocateSheet(SheetType type, int sheetSize)
 		{
 			return new Sheet(type, new Size(sheetSize, sheetSize));
@@ -52,9 +53,16 @@ namespace OpenRA.Graphics
 		{
 			switch (t)
 			{
-				case SpriteFrameType.Indexed: return SheetType.Indexed;
-				case SpriteFrameType.BGRA: return SheetType.BGRA;
-				default: throw new NotImplementedException("Unknown SpriteFrameType {0}".F(t));
+				case SpriteFrameType.Indexed8:
+					return SheetType.Indexed;
+
+				// Util.FastCopyIntoChannel will automatically convert these to BGRA
+				case SpriteFrameType.Bgra32:
+				case SpriteFrameType.Bgr24:
+				case SpriteFrameType.Rgba32:
+				case SpriteFrameType.Rgb24:
+					return SheetType.BGRA;
+				default: throw new NotImplementedException($"Unknown SpriteFrameType {t}");
 			}
 		}

@@ -66,45 +74,36 @@ namespace OpenRA.Graphics

 		public SheetBuilder(SheetType t, Func<Sheet> allocateSheet, int margin = 1)
 		{
-			channel = t == SheetType.Indexed ? TextureChannel.Red : TextureChannel.RGBA;
+			CurrentChannel = t == SheetType.Indexed ? TextureChannel.Red : TextureChannel.RGBA;
 			Type = t;
-			current = allocateSheet();
-			sheets.Add(current);
+			Current = allocateSheet();
+			sheets.Add(Current);
 			this.allocateSheet = allocateSheet;
 			this.margin = margin;
 		}

-		public Sprite Add(ISpriteFrame frame) { return Add(frame.Data, frame.Size, 0, frame.Offset); }
-		public Sprite Add(byte[] src, Size size) { return Add(src, size, 0, float3.Zero); }
-		public Sprite Add(byte[] src, Size size, float zRamp, in float3 spriteOffset)
+		public Sprite Add(ISpriteFrame frame) { return Add(frame.Data, frame.Type, frame.Size, 0, frame.Offset); }
+		public Sprite Add(byte[] src, SpriteFrameType type, Size size) { return Add(src, type, size, 0, float3.Zero); }
+		public Sprite Add(byte[] src, SpriteFrameType type, Size size, float zRamp, in float3 spriteOffset)
 		{
 			// Don't bother allocating empty sprites
 			if (size.Width == 0 || size.Height == 0)
-				return new Sprite(current, Rectangle.Empty, 0, spriteOffset, channel, BlendMode.Alpha);
+				return new Sprite(Current, Rectangle.Empty, 0, spriteOffset, CurrentChannel, BlendMode.Alpha);

 			var rect = Allocate(size, zRamp, spriteOffset);
-			Util.FastCopyIntoChannel(rect, src);
-			current.CommitBufferedData();
+			Util.FastCopyIntoChannel(rect, src, type);
+			Current.CommitBufferedData();
 			return rect;
 		}

 		public Sprite Add(Png src, float scale = 1f)
 		{
-			var rect = Allocate(new Size(src.Width, src.Height),  scale);
+			var rect = Allocate(new Size(src.Width, src.Height), scale);
 			Util.FastCopyIntoSprite(rect, src);
-			current.CommitBufferedData();
+			Current.CommitBufferedData();
 			return rect;
 		}

-		public Sprite Add(Size size, byte paletteIndex)
-		{
-			var data = new byte[size.Width * size.Height];
-			for (var i = 0; i < data.Length; i++)
-				data[i] = paletteIndex;
-
-			return Add(data, size);
-		}
-
 		TextureChannel? NextChannel(TextureChannel t)
 		{
 			var nextChannel = (int)t + (int)Type;
@@ -117,7 +116,7 @@ namespace OpenRA.Graphics
 		public Sprite Allocate(Size imageSize, float scale = 1f) { return Allocate(imageSize, 0, float3.Zero, scale); }
 		public Sprite Allocate(Size imageSize, float zRamp, in float3 spriteOffset, float scale = 1f)
 		{
-			if (imageSize.Width + p.X + margin > current.Size.Width)
+			if (imageSize.Width + p.X + margin > Current.Size.Width)
 			{
 				p = new int2(0, p.Y + rowHeight + margin);
 				rowHeight = imageSize.Height;
@@ -126,33 +125,29 @@ namespace OpenRA.Graphics
 			if (imageSize.Height > rowHeight)
 				rowHeight = imageSize.Height;

-			if (p.Y + imageSize.Height + margin > current.Size.Height)
+			if (p.Y + imageSize.Height + margin > Current.Size.Height)
 			{
-				var next = NextChannel(channel);
+				var next = NextChannel(CurrentChannel);
 				if (next == null)
 				{
-					current.ReleaseBuffer();
-					current = allocateSheet();
-					sheets.Add(current);
-					channel = Type == SheetType.Indexed ? TextureChannel.Red : TextureChannel.RGBA;
+					Current.ReleaseBuffer();
+					Current = allocateSheet();
+					sheets.Add(Current);
+					CurrentChannel = Type == SheetType.Indexed ? TextureChannel.Red : TextureChannel.RGBA;
 				}
 				else
-					channel = next.Value;
+					CurrentChannel = next.Value;

 				rowHeight = imageSize.Height;
 				p = int2.Zero;
 			}

-			var rect = new Sprite(current, new Rectangle(p.X + margin, p.Y + margin, imageSize.Width, imageSize.Height), zRamp, spriteOffset, channel, BlendMode.Alpha, scale);
+			var rect = new Sprite(Current, new Rectangle(p.X + margin, p.Y + margin, imageSize.Width, imageSize.Height), zRamp, spriteOffset, CurrentChannel, BlendMode.Alpha, scale);
 			p += new int2(imageSize.Width + margin, 0);

 			return rect;
 		}

-		public Sheet Current { get { return current; } }
-		public TextureChannel CurrentChannel { get { return channel; } }
-		public IEnumerable<Sheet> AllSheets { get { return sheets; } }
-
 		public void Dispose()
 		{
 			foreach (var sheet in sheets)
--- a/OpenRA.Game/Graphics/Sprite.cs
+++ b/OpenRA.Game/Graphics/Sprite.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -23,7 +23,6 @@ namespace OpenRA.Graphics
 		public readonly float ZRamp;
 		public readonly float3 Size;
 		public readonly float3 Offset;
-		public readonly float3 FractionalOffset;
 		public readonly float Top, Left, Bottom, Right;

 		public Sprite(Sheet sheet, Rectangle bounds, TextureChannel channel, float scale = 1)
@@ -38,13 +37,16 @@ namespace OpenRA.Graphics
 			Channel = channel;
 			Size = scale * new float3(bounds.Size.Width, bounds.Size.Height, bounds.Size.Height * zRamp);
 			BlendMode = blendMode;
-			FractionalOffset = Size.Z != 0 ? offset / Size :
-				new float3(offset.X / Size.X, offset.Y / Size.Y, 0);

-			Left = (float)Math.Min(bounds.Left, bounds.Right) / sheet.Size.Width;
-			Top = (float)Math.Min(bounds.Top, bounds.Bottom) / sheet.Size.Height;
-			Right = (float)Math.Max(bounds.Left, bounds.Right) / sheet.Size.Width;
-			Bottom = (float)Math.Max(bounds.Top, bounds.Bottom) / sheet.Size.Height;
+			// Some GPUs suffer from precision issues when rendering into non 1:1 framebuffers that result
+			// in rendering a line of texels that sample outside the sprite rectangle.
+			// Insetting the texture coordinates by a small fraction of a pixel avoids this
+			// with negligible impact on the 1:1 rendering case.
+			var inset = 1 / 128f;
+			Left = (Math.Min(bounds.Left, bounds.Right) + inset) / sheet.Size.Width;
+			Top = (Math.Min(bounds.Top, bounds.Bottom) + inset) / sheet.Size.Height;
+			Right = (Math.Max(bounds.Left, bounds.Right) - inset) / sheet.Size.Width;
+			Bottom = (Math.Max(bounds.Top, bounds.Bottom) - inset) / sheet.Size.Height;
 		}
 	}

--- a/OpenRA.Game/Graphics/SpriteCache.cs
+++ b/OpenRA.Game/Graphics/SpriteCache.cs
@@ -0,0 +1,174 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using OpenRA.FileSystem;
+using OpenRA.Primitives;
+
+namespace OpenRA.Graphics
+{
+	public sealed class SpriteCache : IDisposable
+	{
+		public readonly Dictionary<SheetType, SheetBuilder> SheetBuilders;
+		readonly ISpriteLoader[] loaders;
+		readonly IReadOnlyFileSystem fileSystem;
+
+		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location)> spriteReservations = new();
+		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location)> frameReservations = new();
+		readonly Dictionary<string, List<int>> reservationsByFilename = new();
+
+		readonly Dictionary<int, ISpriteFrame[]> resolvedFrames = new();
+		readonly Dictionary<int, Sprite[]> resolvedSprites = new();
+
+		readonly Dictionary<int, (string Filename, MiniYamlNode.SourceLocation Location)> missingFiles = new();
+
+		int nextReservationToken = 1;
+
+		public SpriteCache(IReadOnlyFileSystem fileSystem, ISpriteLoader[] loaders, int bgraSheetSize, int indexedSheetSize, int bgraSheetMargin = 1, int indexedSheetMargin = 1)
+		{
+			SheetBuilders = new Dictionary<SheetType, SheetBuilder>
+			{
+				{ SheetType.Indexed, new SheetBuilder(SheetType.Indexed, indexedSheetSize, indexedSheetMargin) },
+				{ SheetType.BGRA, new SheetBuilder(SheetType.BGRA, bgraSheetSize, bgraSheetMargin) }
+			};
+
+			this.fileSystem = fileSystem;
+			this.loaders = loaders;
+		}
+
+		public int ReserveSprites(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location)
+		{
+			var token = nextReservationToken++;
+			spriteReservations[token] = (frames?.ToArray(), location);
+			reservationsByFilename.GetOrAdd(filename, _ => new List<int>()).Add(token);
+			return token;
+		}
+
+		public int ReserveFrames(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location)
+		{
+			var token = nextReservationToken++;
+			frameReservations[token] = (frames?.ToArray(), location);
+			reservationsByFilename.GetOrAdd(filename, _ => new List<int>()).Add(token);
+			return token;
+		}
+
+		static ISpriteFrame[] GetFrames(IReadOnlyFileSystem fileSystem, string filename, ISpriteLoader[] loaders, out TypeDictionary metadata)
+		{
+			metadata = null;
+			if (!fileSystem.TryOpen(filename, out var stream))
+				return null;
+
+			using (stream)
+			{
+				foreach (var loader in loaders)
+					if (loader.TryParseSprite(stream, filename, out var frames, out metadata))
+						return frames;
+
+				return null;
+			}
+		}
+
+		public void LoadReservations(ModData modData)
+		{
+			foreach (var sb in SheetBuilders.Values)
+				sb.Current.CreateBuffer();
+
+			var spriteCache = new Dictionary<int, Sprite>();
+			foreach (var (filename, tokens) in reservationsByFilename)
+			{
+				modData.LoadScreen?.Display();
+				var loadedFrames = GetFrames(fileSystem, filename, loaders, out _);
+				foreach (var token in tokens)
+				{
+					if (frameReservations.TryGetValue(token, out var r))
+					{
+						if (loadedFrames != null)
+						{
+							if (r.Frames != null)
+							{
+								var resolved = new ISpriteFrame[loadedFrames.Length];
+								foreach (var i in r.Frames)
+									resolved[i] = loadedFrames[i];
+								resolvedFrames[token] = resolved;
+							}
+							else
+								resolvedFrames[token] = loadedFrames;
+						}
+						else
+						{
+							resolvedFrames[token] = null;
+							missingFiles[token] = (filename, r.Location);
+						}
+					}
+
+					if (spriteReservations.TryGetValue(token, out r))
+					{
+						if (loadedFrames != null)
+						{
+							var resolved = new Sprite[loadedFrames.Length];
+							var frames = r.Frames ?? Enumerable.Range(0, loadedFrames.Length);
+							foreach (var i in frames)
+								resolved[i] = spriteCache.GetOrAdd(i,
+									f => SheetBuilders[SheetBuilder.FrameTypeToSheetType(loadedFrames[f].Type)].Add(loadedFrames[f]));
+
+							resolvedSprites[token] = resolved;
+						}
+						else
+						{
+							resolvedSprites[token] = null;
+							missingFiles[token] = (filename, r.Location);
+						}
+					}
+				}
+
+				spriteCache.Clear();
+			}
+
+			spriteReservations.Clear();
+			frameReservations.Clear();
+			reservationsByFilename.Clear();
+
+			foreach (var sb in SheetBuilders.Values)
+				sb.Current.ReleaseBuffer();
+		}
+
+		public Sprite[] ResolveSprites(int token)
+		{
+			var resolved = resolvedSprites[token];
+			resolvedSprites.Remove(token);
+			if (missingFiles.TryGetValue(token, out var r))
+				throw new FileNotFoundException($"{r.Location}: {r.Filename} not found", r.Filename);
+
+			return resolved;
+		}
+
+		public ISpriteFrame[] ResolveFrames(int token)
+		{
+			var resolved = resolvedFrames[token];
+			resolvedFrames.Remove(token);
+			if (missingFiles.TryGetValue(token, out var r))
+				throw new FileNotFoundException($"{r.Location}: {r.Filename} not found", r.Filename);
+
+			return resolved;
+		}
+
+		public IEnumerable<(string Filename, MiniYamlNode.SourceLocation Location)> MissingFiles => missingFiles.Values.ToHashSet();
+
+		public void Dispose()
+		{
+			foreach (var sb in SheetBuilders.Values)
+				sb.Dispose();
+		}
+	}
+}
--- a/OpenRA.Game/Graphics/SpriteFont.cs
+++ b/OpenRA.Game/Graphics/SpriteFont.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -10,7 +10,6 @@
 #endregion

 using System;
-using System.Linq;
 using OpenRA.Primitives;
 using OpenRA.Support;

@@ -18,10 +17,9 @@ namespace OpenRA.Graphics
 {
 	public sealed class SpriteFont : IDisposable
 	{
-		public int TopOffset { get; private set; }
+		public int TopOffset { get; }
 		readonly int size;
 		readonly SheetBuilder builder;
-		readonly Func<string, float> lineWidth;
 		readonly IFont font;
 		readonly Cache<char, GlyphInfo> glyphs;
 		readonly Cache<(char C, int Radius), Sprite> contrastGlyphs;
@@ -32,7 +30,7 @@ namespace OpenRA.Graphics
 		public SpriteFont(string name, byte[] data, int size, int ascender, float scale, SheetBuilder builder)
 		{
 			if (builder.Type != SheetType.BGRA)
-				throw new ArgumentException("The sheet builder must create BGRA sheets.", "builder");
+				throw new ArgumentException("The sheet builder must create BGRA sheets.", nameof(builder));

 			deviceScale = scale;
 			this.size = size;
@@ -43,13 +41,9 @@ namespace OpenRA.Graphics
 			contrastGlyphs = new Cache<(char, int), Sprite>(CreateContrastGlyph);
 			dilationElements = new Cache<int, float[]>(CreateCircularWeightMap);

-			// PERF: Cache these delegates for Measure calls.
-			Func<char, float> characterWidth = character => glyphs[character].Advance;
-			lineWidth = line => line.Sum(characterWidth) / deviceScale;
-
 			// Pre-cache small font sizes so glyphs are immediately available when we need them
 			if (size <= 24)
-				using (new PerfTimer("Precache {0} {1}px".F(name, size)))
+				using (new PerfTimer($"Precache {name} {size}px"))
 					for (var n = (char)0x20; n < (char)0x7f; n++)
 						if (glyphs[n] == null)
 							throw new InvalidOperationException();
@@ -89,10 +83,10 @@ namespace OpenRA.Graphics
 				if (g.Sprite != null)
 				{
 					var contrastSprite = contrastGlyphs[(s, screenContrast)];
-					Game.Renderer.RgbaSpriteRenderer.DrawSpriteWithTint(contrastSprite,
+					Game.Renderer.RgbaSpriteRenderer.DrawSprite(contrastSprite,
 						(screen + g.Offset - contrastVector) / deviceScale,
-						contrastSprite.Size / deviceScale,
-						tint);
+						1f / deviceScale,
+						tint, 1f);
 				}

 				screen += new int2((int)(g.Advance + 0.5f), 0);
@@ -120,16 +114,16 @@ namespace OpenRA.Graphics

 				// Convert screen coordinates back to UI coordinates for drawing
 				if (g.Sprite != null)
-					Game.Renderer.RgbaSpriteRenderer.DrawSpriteWithTint(g.Sprite,
+					Game.Renderer.RgbaSpriteRenderer.DrawSprite(g.Sprite,
 					(screen + g.Offset).ToFloat2() / deviceScale,
-					g.Sprite.Size / deviceScale,
-					tint);
+					1f / deviceScale,
+					tint, 1f);

 				screen += new int2((int)(g.Advance + 0.5f), 0);
 			}
 		}

-		float2 Rotate(float2 v, float sina, float cosa, float2 offset)
+		static float2 Rotate(float2 v, float sina, float cosa, float2 offset)
 		{
 			return new float2(
 				v.X * cosa - v.Y * sina + offset.X,
@@ -172,12 +166,12 @@ namespace OpenRA.Graphics

 					// Offset rotated glyph to align the top-left corner with the screen pixel grid
 					var screenOffset = new float2((int)(ra.X * deviceScale + 0.5f), (int)(ra.Y * deviceScale + 0.5f)) / deviceScale - ra;
-					Game.Renderer.RgbaSpriteRenderer.DrawSpriteWithTint(g.Sprite,
+					Game.Renderer.RgbaSpriteRenderer.DrawSprite(g.Sprite,
 						ra + screenOffset,
 						rb + screenOffset,
 						rc + screenOffset,
 						rd + screenOffset,
-						tint);
+						tint, 1f);
 				}

 				p += new float2(g.Advance / deviceScale, 0);
@@ -238,16 +232,26 @@ namespace OpenRA.Graphics
 			if (string.IsNullOrEmpty(text))
 				return new int2(0, size);

-			var lines = text.Split('\n');
-			return new int2((int)Math.Ceiling(MaxLineWidth(lines, lineWidth)), lines.Length * size);
+			var lines = text.SplitLines('\n');
+
+			var maxWidth = 0f;
+			var rows = 0;
+			foreach (var line in lines)
+			{
+				rows++;
+				maxWidth = Math.Max(maxWidth, LineWidth(line));
+			}
+
+			return new int2((int)Math.Ceiling(maxWidth), rows * size);
 		}

-		static float MaxLineWidth(string[] lines, Func<string, float> lineWidth)
+		float LineWidth(ReadOnlySpan<char> line)
 		{
-			var maxWidth = 0f;
-			foreach (var line in lines)
-				maxWidth = Math.Max(maxWidth, lineWidth(line));
-			return maxWidth;
+			var result = 0f;
+			foreach (var c in line)
+				result += glyphs[c].Advance;
+
+			return result / deviceScale;
 		}

 		GlyphInfo CreateGlyph(char c)
@@ -423,7 +427,7 @@ namespace OpenRA.Graphics
 		}
 	}

-	class GlyphInfo
+	sealed class GlyphInfo
 	{
 		public float Advance;
 		public int2 Offset;
--- a/OpenRA.Game/Graphics/SpriteLoader.cs
+++ b/OpenRA.Game/Graphics/SpriteLoader.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -9,20 +9,39 @@
 */
 #endregion

-using System;
-using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 using OpenRA.FileSystem;
 using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
-	public enum SpriteFrameType { Indexed, BGRA }
+	/// <summary>
+	/// Describes the format of the pixel data in a ISpriteFrame.
+	/// Note that the channel order is defined for little-endian bytes, so BGRA corresponds
+	/// to a 32bit ARGB value, such as that returned by Color.ToArgb().
+	/// </summary>
+	public enum SpriteFrameType
+	{
+		// 8 bit index into an external palette
+		Indexed8,
+
+		// 32 bit color such as returned by Color.ToArgb() or the bmp file format
+		// (remember that little-endian systems place the little bits in the first byte!)
+		Bgra32,
+
+		// Like BGRA, but without an alpha channel
+		Bgr24,
+
+		// 32 bit color in big-endian format, like png
+		Rgba32,
+
+		// Like RGBA, but without an alpha channel
+		Rgb24
+	}

 	public interface ISpriteLoader
 	{
-		bool TryParseSprite(Stream s, out ISpriteFrame[] frames, out TypeDictionary metadata);
+		bool TryParseSprite(Stream s, string filename, out ISpriteFrame[] frames, out TypeDictionary metadata);
 	}

 	public interface ISpriteFrame
@@ -45,94 +64,6 @@ namespace OpenRA.Graphics
 		bool DisableExportPadding { get; }
 	}

-	public class SpriteCache
-	{
-		public readonly Cache<SpriteFrameType, SheetBuilder> SheetBuilders;
-		readonly ISpriteLoader[] loaders;
-		readonly IReadOnlyFileSystem fileSystem;
-
-		readonly Dictionary<string, List<Sprite[]>> sprites = new Dictionary<string, List<Sprite[]>>();
-		readonly Dictionary<string, ISpriteFrame[]> unloadedFrames = new Dictionary<string, ISpriteFrame[]>();
-		readonly Dictionary<string, TypeDictionary> metadata = new Dictionary<string, TypeDictionary>();
-
-		public SpriteCache(IReadOnlyFileSystem fileSystem, ISpriteLoader[] loaders)
-		{
-			SheetBuilders = new Cache<SpriteFrameType, SheetBuilder>(t => new SheetBuilder(SheetBuilder.FrameTypeToSheetType(t)));
-
-			this.fileSystem = fileSystem;
-			this.loaders = loaders;
-		}
-
-		/// <summary>
-		/// Returns the first set of sprites with the given filename.
-		/// If getUsedFrames is defined then the indices returned by the function call
-		/// are guaranteed to be loaded.  The value of other indices in the returned
-		/// array are undefined and should never be accessed.
-		/// </summary>
-		public Sprite[] this[string filename, Func<int, IEnumerable<int>> getUsedFrames = null]
-		{
-			get
-			{
-				var allSprites = sprites.GetOrAdd(filename);
-				var sprite = allSprites.FirstOrDefault();
-
-				if (!unloadedFrames.TryGetValue(filename, out var unloaded))
-					unloaded = null;
-
-				// This is the first time that the file has been requested
-				// Load all of the frames into the unused buffer and initialize
-				// the loaded cache (initially empty)
-				if (sprite == null)
-				{
-					unloaded = FrameLoader.GetFrames(fileSystem, filename, loaders, out var fileMetadata);
-					unloadedFrames[filename] = unloaded;
-					metadata[filename] = fileMetadata;
-
-					sprite = new Sprite[unloaded.Length];
-					allSprites.Add(sprite);
-				}
-
-				// HACK: The sequence code relies on side-effects from getUsedFrames
-				var indices = getUsedFrames != null ? getUsedFrames(sprite.Length) :
-					Enumerable.Range(0, sprite.Length);
-
-				// Load any unused frames into the SheetBuilder
-				if (unloaded != null)
-				{
-					foreach (var i in indices)
-					{
-						if (unloaded[i] != null)
-						{
-							sprite[i] = SheetBuilders[unloaded[i].Type].Add(unloaded[i]);
-							unloaded[i] = null;
-						}
-					}
-
-					// All frames have been loaded
-					if (unloaded.All(f => f == null))
-						unloadedFrames.Remove(filename);
-				}
-
-				return sprite;
-			}
-		}
-
-		/// <summary>
-		/// Returns a TypeDictionary containing any metadata defined by the frame
-		/// or null if the frame does not define metadata.
-		/// </summary>
-		public TypeDictionary FrameMetadata(string filename)
-		{
-			if (!metadata.TryGetValue(filename, out var fileMetadata))
-			{
-				FrameLoader.GetFrames(fileSystem, filename, loaders, out fileMetadata);
-				metadata[filename] = fileMetadata;
-			}
-
-			return fileMetadata;
-		}
-	}
-
 	public class FrameCache
 	{
 		readonly Cache<string, ISpriteFrame[]> frames;
@@ -142,7 +73,7 @@ namespace OpenRA.Graphics
 			frames = new Cache<string, ISpriteFrame[]>(filename => FrameLoader.GetFrames(fileSystem, filename, loaders, out _));
 		}

-		public ISpriteFrame[] this[string filename] { get { return frames[filename]; } }
+		public ISpriteFrame[] this[string filename] => frames[filename];
 	}

 	public static class FrameLoader
@@ -151,7 +82,7 @@ namespace OpenRA.Graphics
 		{
 			using (var stream = fileSystem.Open(filename))
 			{
-				var spriteFrames = GetFrames(stream, loaders, out metadata);
+				var spriteFrames = GetFrames(stream, loaders, filename, out metadata);
 				if (spriteFrames == null)
 					throw new InvalidDataException(filename + " is not a valid sprite file!");

@@ -159,12 +90,12 @@ namespace OpenRA.Graphics
 			}
 		}

-		public static ISpriteFrame[] GetFrames(Stream stream, ISpriteLoader[] loaders, out TypeDictionary metadata)
+		public static ISpriteFrame[] GetFrames(Stream stream, ISpriteLoader[] loaders, string filename, out TypeDictionary metadata)
 		{
 			metadata = null;

 			foreach (var loader in loaders)
-				if (loader.TryParseSprite(stream, out var frames, out metadata))
+				if (loader.TryParseSprite(stream, filename, out var frames, out metadata))
 					return frames;

 			return null;
--- a/OpenRA.Game/Graphics/SpriteRenderable.cs
+++ b/OpenRA.Game/Graphics/SpriteRenderable.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -9,79 +9,107 @@
 */
 #endregion

+using System;
 using System.Collections.Generic;
 using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
-	public struct SpriteRenderable : IRenderable, ITintableRenderable, IFinalizedRenderable
+	public class SpriteRenderable : IPalettedRenderable, IModifyableRenderable, IFinalizedRenderable
 	{
-		public static readonly IEnumerable<IRenderable> None = new IRenderable[0];
+		public static readonly IEnumerable<IRenderable> None = Array.Empty<IRenderable>();

 		readonly Sprite sprite;
 		readonly WPos pos;
-		readonly WVec offset;
-		readonly int zOffset;
-		readonly PaletteReference palette;
 		readonly float scale;
-		readonly float3 tint;
-		readonly bool isDecoration;
-		readonly bool ignoreWorldTint;
+		readonly WAngle rotation = WAngle.Zero;

-		public SpriteRenderable(Sprite sprite, WPos pos, WVec offset, int zOffset, PaletteReference palette, float scale, bool isDecoration)
-			: this(sprite, pos, offset, zOffset, palette, scale, float3.Ones, isDecoration, false) { }
-
-		public SpriteRenderable(Sprite sprite, WPos pos, WVec offset, int zOffset, PaletteReference palette, float scale, bool isDecoration, bool ignoreWorldTint)
-			: this(sprite, pos, offset, zOffset, palette, scale, float3.Ones, isDecoration, ignoreWorldTint) { }
-
-		public SpriteRenderable(Sprite sprite, WPos pos, WVec offset, int zOffset, PaletteReference palette, float scale, float3 tint, bool isDecoration, bool ignoreWorldTint)
+		public SpriteRenderable(Sprite sprite, WPos pos, WVec offset, int zOffset, PaletteReference palette, float scale, float alpha,
+			float3 tint, TintModifiers tintModifiers, bool isDecoration, WAngle rotation)
 		{
 			this.sprite = sprite;
 			this.pos = pos;
-			this.offset = offset;
-			this.zOffset = zOffset;
-			this.palette = palette;
+			Offset = offset;
+			ZOffset = zOffset;
+			Palette = palette;
 			this.scale = scale;
-			this.tint = tint;
-			this.isDecoration = isDecoration;
-			this.ignoreWorldTint = ignoreWorldTint;
+			this.rotation = rotation;
+			Tint = tint;
+			IsDecoration = isDecoration;
+			TintModifiers = tintModifiers;
+			Alpha = alpha;
+
+			// PERF: Remove useless palette assignments for RGBA sprites
+			// HACK: This is working around the fact that palettes are defined on traits rather than sequences
+			// and can be removed once this has been fixed
+			if (sprite.Channel == TextureChannel.RGBA && !(palette?.HasColorShift ?? false))
+				Palette = null;
 		}

-		public WPos Pos { get { return pos + offset; } }
-		public WVec Offset { get { return offset; } }
-		public PaletteReference Palette { get { return palette; } }
-		public int ZOffset { get { return zOffset; } }
-		public bool IsDecoration { get { return isDecoration; } }
+		public SpriteRenderable(Sprite sprite, WPos pos, WVec offset, int zOffset, PaletteReference palette, float scale, float alpha,
+			float3 tint, TintModifiers tintModifiers, bool isDecoration)
+			: this(sprite, pos, offset, zOffset, palette, scale, alpha, tint, tintModifiers, isDecoration, WAngle.Zero) { }

-		public IRenderable WithPalette(PaletteReference newPalette) { return new SpriteRenderable(sprite, pos, offset, zOffset, newPalette, scale, tint, isDecoration, ignoreWorldTint); }
-		public IRenderable WithZOffset(int newOffset) { return new SpriteRenderable(sprite, pos, offset, newOffset, palette, scale, tint, isDecoration, ignoreWorldTint); }
-		public IRenderable OffsetBy(WVec vec) { return new SpriteRenderable(sprite, pos + vec, offset, zOffset, palette, scale, tint, isDecoration, ignoreWorldTint); }
-		public IRenderable AsDecoration() { return new SpriteRenderable(sprite, pos, offset, zOffset, palette, scale, tint, true, ignoreWorldTint); }
+		public WPos Pos => pos + Offset;
+		public WVec Offset { get; }
+		public PaletteReference Palette { get; }
+		public int ZOffset { get; }
+		public bool IsDecoration { get; }

-		public IRenderable WithTint(in float3 newTint) { return new SpriteRenderable(sprite, pos, offset, zOffset, palette, scale, newTint, isDecoration, ignoreWorldTint); }
+		public float Alpha { get; }
+		public float3 Tint { get; }
+		public TintModifiers TintModifiers { get; }
+
+		public IPalettedRenderable WithPalette(PaletteReference newPalette)
+		{
+			return new SpriteRenderable(sprite, pos, Offset, ZOffset, newPalette, scale, Alpha, Tint, TintModifiers, IsDecoration, rotation);
+		}
+
+		public IRenderable WithZOffset(int newOffset)
+		{
+			return new SpriteRenderable(sprite, pos, Offset, newOffset, Palette, scale, Alpha, Tint, TintModifiers, IsDecoration, rotation);
+		}
+
+		public IRenderable OffsetBy(in WVec vec)
+		{
+			return new SpriteRenderable(sprite, pos + vec, Offset, ZOffset, Palette, scale, Alpha, Tint, TintModifiers, IsDecoration, rotation);
+		}
+
+		public IRenderable AsDecoration()
+		{
+			return new SpriteRenderable(sprite, pos, Offset, ZOffset, Palette, scale, Alpha, Tint, TintModifiers, true, rotation);
+		}
+
+		public IModifyableRenderable WithAlpha(float newAlpha)
+		{
+			return new SpriteRenderable(sprite, pos, Offset, ZOffset, Palette, scale, newAlpha, Tint, TintModifiers, IsDecoration, rotation);
+		}
+
+		public IModifyableRenderable WithTint(in float3 newTint, TintModifiers newTintModifiers)
+		{
+			return new SpriteRenderable(sprite, pos, Offset, ZOffset, Palette, scale, Alpha, newTint, newTintModifiers, IsDecoration, rotation);
+		}

 		float3 ScreenPosition(WorldRenderer wr)
 		{
-			var xy = wr.ScreenPxPosition(pos) + wr.ScreenPxOffset(offset) - (0.5f * scale * sprite.Size.XY).ToInt2();
-
-			// HACK: The z offset needs to be applied somewhere, but this probably is the wrong place.
-			return new float3(xy, sprite.Offset.Z + wr.ScreenZPosition(pos, 0) - 0.5f * scale * sprite.Size.Z);
+			var s = 0.5f * scale * sprite.Size;
+			return wr.Screen3DPxPosition(pos) + wr.ScreenPxOffset(Offset) - new float3((int)s.X, (int)s.Y, s.Z);
 		}

 		public IFinalizedRenderable PrepareRender(WorldRenderer wr) { return this; }
 		public void Render(WorldRenderer wr)
 		{
 			var wsr = Game.Renderer.WorldSpriteRenderer;
-			if (ignoreWorldTint)
-				wsr.DrawSprite(sprite, ScreenPosition(wr), palette, scale * sprite.Size);
-			else
-			{
-				var t = tint;
-				if (wr.TerrainLighting != null)
-					t *= wr.TerrainLighting.TintAt(pos);
+			var t = Alpha * Tint;
+			if (wr.TerrainLighting != null && (TintModifiers & TintModifiers.IgnoreWorldTint) == 0)
+				t *= wr.TerrainLighting.TintAt(pos);

-				wsr.DrawSpriteWithTint(sprite, ScreenPosition(wr), palette, scale * sprite.Size, t);
-			}
+			// Shader interprets negative alpha as a flag to use the tint colour directly instead of multiplying the sprite colour
+			var a = Alpha;
+			if ((TintModifiers & TintModifiers.ReplaceColor) != 0)
+				a *= -1;
+
+			wsr.DrawSprite(sprite, Palette, ScreenPosition(wr), scale, t, a, rotation.RendererRadians());
 		}

 		public void RenderDebugGeometry(WorldRenderer wr)
@@ -89,13 +117,16 @@ namespace OpenRA.Graphics
 			var pos = ScreenPosition(wr) + sprite.Offset;
 			var tl = wr.Viewport.WorldToViewPx(pos);
 			var br = wr.Viewport.WorldToViewPx(pos + sprite.Size);
-			Game.Renderer.RgbaColorRenderer.DrawRect(tl, br, 1, Color.Red);
+			if (rotation == WAngle.Zero)
+				Game.Renderer.RgbaColorRenderer.DrawRect(tl, br, 1, Color.Red);
+			else
+				Game.Renderer.RgbaColorRenderer.DrawPolygon(Util.RotateQuad(tl, br - tl, rotation.RendererRadians()), 1, Color.Red);
 		}

 		public Rectangle ScreenBounds(WorldRenderer wr)
 		{
 			var screenOffset = ScreenPosition(wr) + sprite.Offset;
-			return new Rectangle((int)screenOffset.X, (int)screenOffset.Y, (int)sprite.Size.X, (int)sprite.Size.Y);
+			return Util.BoundingRectangle(screenOffset, sprite.Size, rotation.RendererRadians());
 		}
 	}
 }
--- a/OpenRA.Game/Graphics/SpriteRenderer.cs
+++ b/OpenRA.Game/Graphics/SpriteRenderer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -10,20 +10,20 @@
 #endregion

 using System;
-using System.Linq;
+using System.Collections.Generic;
 using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
 	public class SpriteRenderer : Renderer.IBatchRenderer
 	{
-		const int SheetCount = 7;
-		static readonly string[] SheetIndexToTextureName = Exts.MakeArray(SheetCount, i => "Texture{0}".F(i));
+		public const int SheetCount = 8;
+		static readonly string[] SheetIndexToTextureName = Exts.MakeArray(SheetCount, i => $"Texture{i}");

 		readonly Renderer renderer;
 		readonly IShader shader;

-		readonly Vertex[] vertices;
+		Vertex[] vertices;
 		readonly Sheet[] sheets = new Sheet[SheetCount];

 		BlendMode currentBlend = BlendMode.Alpha;
@@ -34,7 +34,7 @@ namespace OpenRA.Graphics
 		{
 			this.renderer = renderer;
 			this.shader = shader;
-			vertices = new Vertex[renderer.TempBufferSize];
+			vertices = renderer.Context.CreateVertices(renderer.TempBufferSize);
 		}

 		public void Flush()
@@ -49,7 +49,9 @@ namespace OpenRA.Graphics

 				renderer.Context.SetBlendMode(currentBlend);
 				shader.PrepareRender();
-				renderer.DrawBatch(vertices, nv, PrimitiveType.TriangleList);
+
+				// PERF: The renderer may choose to replace vertices with a different temporary buffer.
+				renderer.DrawBatch(ref vertices, nv, PrimitiveType.TriangleList);
 				renderer.Context.SetBlendMode(BlendMode.None);

 				nv = 0;
@@ -81,119 +83,170 @@ namespace OpenRA.Graphics
 				for (; secondarySheetIndex < ns; secondarySheetIndex++)
 					if (sheets[secondarySheetIndex] == secondarySheet)
 						break;
+
+				// If neither sheet has been mapped both index values will be set to ns.
+				// This is fine if they both reference the same texture, but if they don't
+				// we must increment the secondary sheet index to the next free sampler.
+				if (secondarySheetIndex == sheetIndex && secondarySheet != sheet)
+					secondarySheetIndex++;
 			}

 			// Make sure that we have enough free samplers to map both if needed, otherwise flush
-			var needSamplers = (sheetIndex == ns ? 1 : 0) + (secondarySheetIndex == ns ? 1 : 0);
-			if (ns + needSamplers >= sheets.Length)
+			if (Math.Max(sheetIndex, secondarySheetIndex) >= sheets.Length)
 			{
 				Flush();
 				sheetIndex = 0;
-				if (ss != null)
-					secondarySheetIndex = 1;
+				secondarySheetIndex = ss != null && ss.SecondarySheet != sheet ? 1 : 0;
 			}

 			if (sheetIndex >= ns)
 			{
 				sheets[sheetIndex] = sheet;
-				ns += 1;
+				ns++;
 			}

 			if (secondarySheetIndex >= ns && ss != null)
 			{
 				sheets[secondarySheetIndex] = ss.SecondarySheet;
-				ns += 1;
+				ns++;
 			}

 			return new int2(sheetIndex, secondarySheetIndex);
 		}

-		internal void DrawSprite(Sprite s, in float3 location, float paletteTextureIndex, in float3 size)
+		static float ResolveTextureIndex(Sprite s, PaletteReference pal)
+		{
+			if (pal == null)
+				return 0;
+
+			// PERF: Remove useless palette assignments for RGBA sprites
+			// HACK: This is working around the limitation that palettes are defined on traits rather than on sequences,
+			// and can be removed once this has been fixed
+			if (s.Channel == TextureChannel.RGBA && !pal.HasColorShift)
+				return 0;
+
+			return pal.TextureIndex;
+		}
+
+		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 location, in float3 scale, float rotation = 0f)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, location + s.FractionalOffset * size, s, samplers, paletteTextureIndex, nv, size, float3.Ones);
+			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, nv, scale * s.Size, float3.Ones,
+								1f, rotation);
 			nv += 6;
 		}

-		public void DrawSprite(Sprite s, in float3 location, PaletteReference pal)
-		{
-			DrawSprite(s, location, pal.TextureIndex, s.Size);
-		}
-
-		public void DrawSprite(Sprite s, in float3 location, PaletteReference pal, float3 size)
-		{
-			DrawSprite(s, location, pal.TextureIndex, size);
-		}
-
-		public void DrawSprite(Sprite s, in float3 a, in float3 b, in float3 c, in float3 d)
+		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 location, float scale, float rotation = 0f)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, a, b, c, d, s, samplers, 0, float3.Ones, nv);
+			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, nv, scale * s.Size, float3.Ones,
+								1f, rotation);
 			nv += 6;
 		}

-		internal void DrawSpriteWithTint(Sprite s, in float3 location, float paletteTextureIndex, in float3 size, in float3 tint)
+		public void DrawSprite(Sprite s, PaletteReference pal, in float3 location, float scale = 1f, float rotation = 0f)
+		{
+			DrawSprite(s, ResolveTextureIndex(s, pal), location, scale, rotation);
+		}
+
+		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 location, float scale, in float3 tint, float alpha,
+			float rotation = 0f)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, location + s.FractionalOffset * size, s, samplers, paletteTextureIndex, nv, size, tint);
+			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, nv, scale * s.Size, tint, alpha,
+								rotation);
 			nv += 6;
 		}

-		public void DrawSpriteWithTint(Sprite s, in float3 location, PaletteReference pal, in float3 size, in float3 tint)
+		public void DrawSprite(Sprite s, PaletteReference pal, in float3 location, float scale, in float3 tint, float alpha,
+			float rotation = 0f)
 		{
-			DrawSpriteWithTint(s, location, pal.TextureIndex, size, tint);
+			DrawSprite(s, ResolveTextureIndex(s, pal), location, scale, tint, alpha, rotation);
 		}

-		public void DrawSpriteWithTint(Sprite s, in float3 a, in float3 b, in float3 c, in float3 d, in float3 tint)
+		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 a, in float3 b, in float3 c, in float3 d, in float3 tint, float alpha)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, a, b, c, d, s, samplers, 0, tint, nv);
+			Util.FastCreateQuad(vertices, a, b, c, d, s, samplers, paletteTextureIndex, tint, alpha, nv);
 			nv += 6;
 		}

-		public void DrawVertexBuffer(IVertexBuffer<Vertex> buffer, int start, int length, PrimitiveType type, Sheet sheet, BlendMode blendMode)
+		public void DrawVertexBuffer(IVertexBuffer<Vertex> buffer, int start, int length, PrimitiveType type, IEnumerable<Sheet> sheets, BlendMode blendMode)
 		{
-			shader.SetTexture("Texture0", sheet.GetTexture());
+			var i = 0;
+			foreach (var s in sheets)
+			{
+				if (i >= SheetCount)
+					ThrowSheetOverflow(nameof(sheets));
+
+				if (s != null)
+					shader.SetTexture(SheetIndexToTextureName[i++], s.GetTexture());
+			}
+
 			renderer.Context.SetBlendMode(blendMode);
 			shader.PrepareRender();
 			renderer.DrawBatch(buffer, start, length, type);
 			renderer.Context.SetBlendMode(BlendMode.None);
 		}

+		// PERF: methods that throw won't be inlined by the JIT, so extract a static helper for use on hot paths
+		static void ThrowSheetOverflow(string paramName)
+		{
+			throw new ArgumentException($"SpriteRenderer only supports {SheetCount} simultaneous textures", paramName);
+		}
+
 		// For RGBAColorRenderer
-		internal void DrawRGBAVertices(Vertex[] v)
+		internal void DrawRGBAVertices(Vertex[] v, BlendMode blendMode)
 		{
 			renderer.CurrentBatchRenderer = this;

-			if (currentBlend != BlendMode.Alpha || nv + v.Length > renderer.TempBufferSize)
+			if (currentBlend != blendMode || nv + v.Length > renderer.TempBufferSize)
 				Flush();

-			currentBlend = BlendMode.Alpha;
+			currentBlend = blendMode;
 			Array.Copy(v, 0, vertices, nv, v.Length);
 			nv += v.Length;
 		}

-		public void SetPalette(ITexture palette)
+		public void SetPalette(ITexture palette, ITexture colorShifts)
 		{
 			shader.SetTexture("Palette", palette);
+			shader.SetTexture("ColorShifts", colorShifts);
 		}

-		public void SetViewportParams(Size screen, float depthScale, float depthOffset, int2 scroll)
+		public void SetViewportParams(Size sheetSize, int downscale, float depthMargin, int2 scroll)
 		{
-			shader.SetVec("Scroll", scroll.X, scroll.Y, scroll.Y);
-			shader.SetVec("r1",
-				2f / screen.Width,
-				2f / screen.Height,
-				-depthScale / screen.Height);
-			shader.SetVec("r2", -1, -1, 1 - depthOffset);
+			// Calculate the scale (r1) and offset (r2) that convert from OpenRA viewport pixels
+			// to OpenGL normalized device coordinates (NDC). OpenGL expects coordinates to vary from [-1, 1],
+			// so we rescale viewport pixels to the range [0, 2] using r1 then subtract 1 using r2.
+			var width = 2f / (downscale * sheetSize.Width);
+			var height = 2f / (downscale * sheetSize.Height);

-			// Texture index is sampled as a float, so convert to pixels then scale
-			shader.SetVec("DepthTextureScale", 128 * depthScale / screen.Height);
+			// Depth is more complicated:
+			// * The OpenGL z axis is inverted (negative is closer) relative to OpenRA (positive is closer).
+			// * We want to avoid clipping pixels that are behind the nominal z == y plane at the
+			//   top of the map, or above the nominal z == y plane at the bottom of the map.
+			//   We therefore expand the depth range by an extra margin that is calculated based on
+			//   the maximum expected world height (see Renderer.InitializeDepthBuffer).
+			// * Sprites can specify an additional per-pixel depth offset map, which is applied in the
+			//   fragment shader. The fragment shader operates in OpenGL window coordinates, not NDC,
+			//   with a depth range [0, 1] corresponding to the NDC [-1, 1]. We must therefore multiply the
+			//   sprite channel value [0, 1] by 255 to find the pixel depth offset, then by our depth scale
+			//   to find the equivalent NDC offset, then divide by 2 to find the window coordinate offset.
+			// * If depthMargin == 0 (which indicates per-pixel depth testing is disabled) sprites that
+			//   extend beyond the top of bottom edges of the screen may be pushed outside [-1, 1] and
+			//   culled by the GPU. We avoid this by forcing everything into the z = 0 plane.
+			var depth = depthMargin != 0f ? 2f / (downscale * (sheetSize.Height + depthMargin)) : 0;
+			shader.SetVec("DepthTextureScale", 128 * depth);
+			shader.SetVec("Scroll", scroll.X, scroll.Y, depthMargin != 0f ? scroll.Y : 0);
+			shader.SetVec("r1", width, height, -depth);
+			shader.SetVec("r2", -1, -1, depthMargin != 0f ? 1 : 0);
 		}

-		public void SetDepthPreviewEnabled(bool enabled)
+		public void SetDepthPreview(bool enabled, float contrast, float offset)
 		{
 			shader.SetBool("EnableDepthPreview", enabled);
+			shader.SetVec("DepthPreviewParams", contrast, offset);
 		}

 		public void SetAntialiasingPixelsPerTexel(float pxPerTx)
--- a/OpenRA.Game/Graphics/TargetLineRenderable.cs
+++ b/OpenRA.Game/Graphics/TargetLineRenderable.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -15,14 +15,14 @@ using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
-	public struct TargetLineRenderable : IRenderable, IFinalizedRenderable
+	public class TargetLineRenderable : IRenderable, IFinalizedRenderable
 	{
 		readonly IEnumerable<WPos> waypoints;
 		readonly Color color;
 		readonly int width;
 		readonly int markerSize;

-		public TargetLineRenderable(IEnumerable<WPos> waypoints, Color color, int width = 1, int markerSize = 1)
+		public TargetLineRenderable(IEnumerable<WPos> waypoints, Color color, int width, int markerSize)
 		{
 			this.waypoints = waypoints;
 			this.color = color;
@@ -30,14 +30,19 @@ namespace OpenRA.Graphics
 			this.markerSize = markerSize;
 		}

-		public WPos Pos { get { return waypoints.First(); } }
-		public PaletteReference Palette { get { return null; } }
-		public int ZOffset { get { return 0; } }
-		public bool IsDecoration { get { return true; } }
+		public WPos Pos => waypoints.First();
+		public int ZOffset => 0;
+		public bool IsDecoration => true;
+
+		public IRenderable WithZOffset(int newOffset) { return this; }
+
+		public IRenderable OffsetBy(in WVec vec)
+		{
+			// Lambdas can't use 'in' variables, so capture a copy for later
+			var offset = vec;
+			return new TargetLineRenderable(waypoints.Select(w => w + offset), color, width, markerSize);
+		}

-		public IRenderable WithPalette(PaletteReference newPalette) { return new TargetLineRenderable(waypoints, color); }
-		public IRenderable WithZOffset(int newOffset) { return new TargetLineRenderable(waypoints, color); }
-		public IRenderable OffsetBy(WVec vec) { return new TargetLineRenderable(waypoints.Select(w => w + vec), color); }
 		public IRenderable AsDecoration() { return this; }

 		public IFinalizedRenderable PrepareRender(WorldRenderer wr) { return this; }
@@ -51,14 +56,14 @@ namespace OpenRA.Graphics
 			foreach (var b in waypoints.Skip(1).Select(pos => wr.Viewport.WorldToViewPx(wr.Screen3DPosition(pos))))
 			{
 				Game.Renderer.RgbaColorRenderer.DrawLine(a, b, width, color);
-				DrawTargetMarker(wr, color, b, markerSize);
+				DrawTargetMarker(color, b, markerSize);
 				a = b;
 			}

-			DrawTargetMarker(wr, color, first);
+			DrawTargetMarker(color, first);
 		}

-		public static void DrawTargetMarker(WorldRenderer wr, Color color, int2 screenPos, int size = 1)
+		public static void DrawTargetMarker(Color color, int2 screenPos, int size = 1)
 		{
 			var offset = new int2(size, size);
 			var tl = screenPos - offset;
--- a/OpenRA.Game/Graphics/TerrainSpriteLayer.cs
+++ b/OpenRA.Game/Graphics/TerrainSpriteLayer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -12,7 +12,6 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
@@ -20,37 +19,37 @@ namespace OpenRA.Graphics
 	{
 		static readonly int[] CornerVertexMap = { 0, 1, 2, 2, 3, 0 };

-		public readonly Sheet Sheet;
 		public readonly BlendMode BlendMode;

+		readonly Sheet[] sheets;
 		readonly Sprite emptySprite;

 		readonly IVertexBuffer<Vertex> vertexBuffer;
 		readonly Vertex[] vertices;
 		readonly bool[] ignoreTint;
-		readonly HashSet<int> dirtyRows = new HashSet<int>();
+		readonly HashSet<int> dirtyRows = new();
 		readonly int rowStride;
 		readonly bool restrictToBounds;

 		readonly WorldRenderer worldRenderer;
 		readonly Map map;

-		readonly PaletteReference palette;
+		readonly PaletteReference[] palettes;

-		public TerrainSpriteLayer(World world, WorldRenderer wr, Sheet sheet, BlendMode blendMode, PaletteReference palette, bool restrictToBounds)
+		public TerrainSpriteLayer(World world, WorldRenderer wr, Sprite emptySprite, BlendMode blendMode, bool restrictToBounds)
 		{
 			worldRenderer = wr;
 			this.restrictToBounds = restrictToBounds;
-			Sheet = sheet;
+			this.emptySprite = emptySprite;
+			sheets = new Sheet[SpriteRenderer.SheetCount];
 			BlendMode = blendMode;
-			this.palette = palette;

 			map = world.Map;
 			rowStride = 6 * map.MapSize.X;

 			vertices = new Vertex[rowStride * map.MapSize.Y];
+			palettes = new PaletteReference[map.MapSize.X * map.MapSize.Y];
 			vertexBuffer = Game.Renderer.Context.CreateVertexBuffer(vertices.Length);
-			emptySprite = new Sprite(sheet, Rectangle.Empty, TextureChannel.Alpha);

 			wr.PaletteInvalidated += UpdatePaletteIndices;

@@ -63,12 +62,11 @@ namespace OpenRA.Graphics

 		void UpdatePaletteIndices()
 		{
-			// Everything in the layer uses the same palette,
-			// so we can fix the indices in one pass
 			for (var i = 0; i < vertices.Length; i++)
 			{
 				var v = vertices[i];
-				vertices[i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, palette.TextureIndex, v.C, v.R, v.G, v.B);
+				var p = palettes[i / 6]?.TextureIndex ?? 0;
+				vertices[i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, p, v.C, v.R, v.G, v.B, v.A);
 			}

 			for (var row = 0; row < map.MapSize.Y; row++)
@@ -77,24 +75,24 @@ namespace OpenRA.Graphics

 		public void Clear(CPos cell)
 		{
-			Update(cell, null, true);
+			Update(cell, null, null, 1f, 1f, true);
 		}

-		public void Update(CPos cell, ISpriteSequence sequence, int frame)
+		public void Update(CPos cell, ISpriteSequence sequence, PaletteReference palette, int frame)
 		{
-			Update(cell, sequence.GetSprite(frame), sequence.IgnoreWorldTint);
+			Update(cell, sequence.GetSprite(frame), palette, sequence.Scale, sequence.GetAlpha(frame), sequence.IgnoreWorldTint);
 		}

-		public void Update(CPos cell, Sprite sprite, bool ignoreTint)
+		public void Update(CPos cell, Sprite sprite, PaletteReference palette, float scale = 1f, float alpha = 1f, bool ignoreTint = false)
 		{
 			var xyz = float3.Zero;
 			if (sprite != null)
 			{
 				var cellOrigin = map.CenterOfCell(cell) - new WVec(0, 0, map.Grid.Ramps[map.Ramp[cell]].CenterHeightOffset);
-				xyz = worldRenderer.Screen3DPosition(cellOrigin) + sprite.Offset - 0.5f * sprite.Size;
+				xyz = worldRenderer.Screen3DPosition(cellOrigin) + scale * (sprite.Offset - 0.5f * sprite.Size);
 			}

-			Update(cell.ToMPos(map.Grid.Type), sprite, xyz, ignoreTint);
+			Update(cell.ToMPos(map.Grid.Type), sprite, palette, xyz, scale, alpha, ignoreTint);
 		}

 		void UpdateTint(MPos uv)
@@ -102,11 +100,10 @@ namespace OpenRA.Graphics
 			var offset = rowStride * uv.V + 6 * uv.U;
 			if (ignoreTint[offset])
 			{
-				var noTint = float3.Ones;
 				for (var i = 0; i < 6; i++)
 				{
 					var v = vertices[offset + i];
-					vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, palette.TextureIndex, v.C, noTint);
+					vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, v.P, v.C, v.A * float3.Ones, v.A);
 				}

 				return;
@@ -117,7 +114,7 @@ namespace OpenRA.Graphics
 			// transparent for isometric tiles
 			var tl = worldRenderer.TerrainLighting;
 			var pos = map.CenterOfCell(uv.ToCPos(map));
-			var step = map.Grid.Type == MapGridType.RectangularIsometric ? 724 : 512;
+			var step = map.Grid.TileScale / 2;
 			var weights = new[]
 			{
 				tl.TintAt(pos + new WVec(-step, -step, 0)),
@@ -131,31 +128,61 @@ namespace OpenRA.Graphics
 			for (var i = 0; i < 6; i++)
 			{
 				var v = vertices[offset + i];
-				vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, palette.TextureIndex, v.C, weights[CornerVertexMap[i]]);
+				vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, v.P, v.C, v.A * weights[CornerVertexMap[i]], v.A);
 			}

 			dirtyRows.Add(uv.V);
 		}

-		public void Update(MPos uv, Sprite sprite, in float3 pos, bool ignoreTint)
+		int GetOrAddSheetIndex(Sheet sheet)
 		{
+			if (sheet == null)
+				return 0;
+
+			for (var i = 0; i < sheets.Length; i++)
+			{
+				if (sheets[i] == sheet)
+					return i;
+
+				if (sheets[i] == null)
+				{
+					sheets[i] = sheet;
+					return i;
+				}
+			}
+
+			throw new InvalidDataException("Sheet overflow");
+		}
+
+		public void Update(MPos uv, Sprite sprite, PaletteReference palette, in float3 pos, float scale, float alpha, bool ignoreTint)
+		{
+			int2 samplers;
 			if (sprite != null)
 			{
-				if (sprite.Sheet != Sheet)
-					throw new InvalidDataException("Attempted to add sprite from a different sheet");
-
 				if (sprite.BlendMode != BlendMode)
 					throw new InvalidDataException("Attempted to add sprite with a different blend mode");
+
+				samplers = new int2(GetOrAddSheetIndex(sprite.Sheet), GetOrAddSheetIndex((sprite as SpriteWithSecondaryData)?.SecondarySheet));
+
+				// PERF: Remove useless palette assignments for RGBA sprites
+				// HACK: This is working around the limitation that palettes are defined on traits rather than on sequences,
+				// and can be removed once this has been fixed
+				if (sprite.Channel == TextureChannel.RGBA && !(palette?.HasColorShift ?? false))
+					palette = null;
 			}
 			else
+			{
 				sprite = emptySprite;
+				samplers = int2.Zero;
+			}

 			// The vertex buffer does not have geometry for cells outside the map
 			if (!map.Tiles.Contains(uv))
 				return;

 			var offset = rowStride * uv.V + 6 * uv.U;
-			Util.FastCreateQuad(vertices, pos, sprite, int2.Zero, palette.TextureIndex, offset, sprite.Size, float3.Ones);
+			Util.FastCreateQuad(vertices, pos, sprite, samplers, palette?.TextureIndex ?? 0, offset, scale * sprite.Size, alpha * float3.Ones, alpha);
+			palettes[uv.V * map.MapSize.X + uv.U] = palette;

 			if (worldRenderer.TerrainLighting != null)
 			{
@@ -188,7 +215,7 @@ namespace OpenRA.Graphics

 			Game.Renderer.WorldSpriteRenderer.DrawVertexBuffer(
 				vertexBuffer, rowStride * firstRow, rowStride * (lastRow - firstRow),
-				PrimitiveType.TriangleList, Sheet, BlendMode);
+				PrimitiveType.TriangleList, sheets, BlendMode);

 			Game.Renderer.Flush();
 		}
--- a/OpenRA.Game/Graphics/Theater.cs
+++ b/OpenRA.Game/Graphics/Theater.cs
@@ -1,197 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using OpenRA.Primitives;
-using OpenRA.Support;
-
-namespace OpenRA.Graphics
-{
-	class TheaterTemplate
-	{
-		public readonly Sprite[] Sprites;
-		public readonly int Stride;
-		public readonly int Variants;
-
-		public TheaterTemplate(Sprite[] sprites, int stride, int variants)
-		{
-			Sprites = sprites;
-			Stride = stride;
-			Variants = variants;
-		}
-	}
-
-	public sealed class Theater : IDisposable
-	{
-		readonly Dictionary<ushort, TheaterTemplate> templates = new Dictionary<ushort, TheaterTemplate>();
-		SheetBuilder sheetBuilder;
-		readonly Sprite missingTile;
-		readonly MersenneTwister random;
-		TileSet tileset;
-
-		public Theater(TileSet tileset, Action<uint, string> onMissingImage = null)
-		{
-			this.tileset = tileset;
-			var allocated = false;
-
-			Func<Sheet> allocate = () =>
-			{
-				if (allocated)
-					throw new SheetOverflowException("Terrain sheet overflow. Try increasing the tileset SheetSize parameter.");
-				allocated = true;
-
-				return new Sheet(SheetType.Indexed, new Size(tileset.SheetSize, tileset.SheetSize));
-			};
-
-			random = new MersenneTwister();
-
-			var frameCache = new FrameCache(Game.ModData.DefaultFileSystem, Game.ModData.SpriteLoaders);
-			foreach (var t in tileset.Templates)
-			{
-				var variants = new List<Sprite[]>();
-
-				foreach (var i in t.Value.Images)
-				{
-					ISpriteFrame[] allFrames;
-					if (onMissingImage != null)
-					{
-						try
-						{
-							allFrames = frameCache[i];
-						}
-						catch (FileNotFoundException)
-						{
-							onMissingImage(t.Key, i);
-							continue;
-						}
-					}
-					else
-						allFrames = frameCache[i];
-
-					var frameCount = tileset.EnableDepth ? allFrames.Length / 2 : allFrames.Length;
-					var indices = t.Value.Frames != null ? t.Value.Frames : Exts.MakeArray(t.Value.TilesCount, j => j);
-
-					var start = indices.Min();
-					var end = indices.Max();
-					if (start < 0 || end >= frameCount)
-						throw new YamlException("Template `{0}` uses frames [{1}..{2}] of {3}, but only [0..{4}] actually exist"
-							.F(t.Key, start, end, i, frameCount - 1));
-
-					variants.Add(indices.Select(j =>
-					{
-						var f = allFrames[j];
-						var tile = t.Value.Contains(j) ? t.Value[j] : null;
-
-						// The internal z axis is inverted from expectation (negative is closer)
-						var zOffset = tile != null ? -tile.ZOffset : 0;
-						var zRamp = tile != null ? tile.ZRamp : 1f;
-						var offset = new float3(f.Offset, zOffset);
-						var type = SheetBuilder.FrameTypeToSheetType(f.Type);
-
-						// Defer SheetBuilder creation until we know what type of frames we are loading!
-						// TODO: Support mixed indexed and BGRA frames
-						if (sheetBuilder == null)
-							sheetBuilder = new SheetBuilder(SheetBuilder.FrameTypeToSheetType(f.Type), allocate);
-						else if (type != sheetBuilder.Type)
-							throw new YamlException("Sprite type mismatch. Terrain sprites must all be either Indexed or RGBA.");
-
-						var s = sheetBuilder.Allocate(f.Size, zRamp, offset);
-						Util.FastCopyIntoChannel(s, f.Data);
-
-						if (tileset.EnableDepth)
-						{
-							var ss = sheetBuilder.Allocate(f.Size, zRamp, offset);
-							Util.FastCopyIntoChannel(ss, allFrames[j + frameCount].Data);
-
-							// s and ss are guaranteed to use the same sheet
-							// because of the custom terrain sheet allocation
-							s = new SpriteWithSecondaryData(s, s.Sheet, ss.Bounds, ss.Channel);
-						}
-
-						return s;
-					}).ToArray());
-				}
-
-				var allSprites = variants.SelectMany(s => s);
-
-				// Ignore the offsets baked into R8 sprites
-				if (tileset.IgnoreTileSpriteOffsets)
-					allSprites = allSprites.Select(s => new Sprite(s.Sheet, s.Bounds, s.ZRamp, new float3(float2.Zero, s.Offset.Z), s.Channel, s.BlendMode));
-
-				if (onMissingImage != null && !variants.Any())
-					continue;
-
-				templates.Add(t.Value.Id, new TheaterTemplate(allSprites.ToArray(), variants.First().Count(), t.Value.Images.Length));
-			}
-
-			// 1x1px transparent tile
-			missingTile = sheetBuilder.Add(new byte[sheetBuilder.Type == SheetType.BGRA ? 4 : 1], new Size(1, 1));
-
-			Sheet.ReleaseBuffer();
-		}
-
-		public bool HasTileSprite(TerrainTile r, int? variant = null)
-		{
-			return TileSprite(r, variant) != missingTile;
-		}
-
-		public Sprite TileSprite(TerrainTile r, int? variant = null)
-		{
-			if (!templates.TryGetValue(r.Type, out var template))
-				return missingTile;
-
-			if (r.Index >= template.Stride)
-				return missingTile;
-
-			var start = template.Variants > 1 ? variant.HasValue ? variant.Value : random.Next(template.Variants) : 0;
-			return template.Sprites[start * template.Stride + r.Index];
-		}
-
-		public Rectangle TemplateBounds(TerrainTemplateInfo template, Size tileSize, MapGridType mapGrid)
-		{
-			Rectangle? templateRect = null;
-
-			var i = 0;
-			for (var y = 0; y < template.Size.Y; y++)
-			{
-				for (var x = 0; x < template.Size.X; x++)
-				{
-					var tile = new TerrainTile(template.Id, (byte)(i++));
-					var tileInfo = tileset.GetTileInfo(tile);
-
-					// Empty tile
-					if (tileInfo == null)
-						continue;
-
-					var sprite = TileSprite(tile);
-					var u = mapGrid == MapGridType.Rectangular ? x : (x - y) / 2f;
-					var v = mapGrid == MapGridType.Rectangular ? y : (x + y) / 2f;
-
-					var tl = new float2(u * tileSize.Width, (v - 0.5f * tileInfo.Height) * tileSize.Height) - 0.5f * sprite.Size;
-					var rect = new Rectangle((int)(tl.X + sprite.Offset.X), (int)(tl.Y + sprite.Offset.Y), (int)sprite.Size.X, (int)sprite.Size.Y);
-					templateRect = templateRect.HasValue ? Rectangle.Union(templateRect.Value, rect) : rect;
-				}
-			}
-
-			return templateRect.HasValue ? templateRect.Value : Rectangle.Empty;
-		}
-
-		public Sheet Sheet { get { return sheetBuilder.Current; } }
-
-		public void Dispose()
-		{
-			sheetBuilder.Dispose();
-		}
-	}
-}
--- a/OpenRA.Game/Graphics/UISpriteRenderable.cs
+++ b/OpenRA.Game/Graphics/UISpriteRenderable.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -13,54 +13,64 @@ using OpenRA.Primitives;

 namespace OpenRA.Graphics
 {
-	public struct UISpriteRenderable : IRenderable, IFinalizedRenderable
+	public class UISpriteRenderable : IRenderable, IPalettedRenderable, IFinalizedRenderable
 	{
 		readonly Sprite sprite;
-		readonly WPos effectiveWorldPos;
 		readonly int2 screenPos;
-		readonly int zOffset;
-		readonly PaletteReference palette;
 		readonly float scale;
+		readonly float alpha;
+		readonly float rotation = 0f;

-		public UISpriteRenderable(Sprite sprite, WPos effectiveWorldPos, int2 screenPos, int zOffset, PaletteReference palette, float scale)
+		public UISpriteRenderable(Sprite sprite, WPos effectiveWorldPos, int2 screenPos, int zOffset, PaletteReference palette, float scale = 1f, float alpha = 1f, float rotation = 0f)
 		{
 			this.sprite = sprite;
-			this.effectiveWorldPos = effectiveWorldPos;
+			Pos = effectiveWorldPos;
 			this.screenPos = screenPos;
-			this.zOffset = zOffset;
-			this.palette = palette;
+			ZOffset = zOffset;
+			Palette = palette;
 			this.scale = scale;
+			this.alpha = alpha;
+			this.rotation = rotation;
+
+			// PERF: Remove useless palette assignments for RGBA sprites
+			// HACK: This is working around the fact that palettes are defined on traits rather than sequences
+			// and can be removed once this has been fixed
+			if (sprite.Channel == TextureChannel.RGBA && !(palette?.HasColorShift ?? false))
+				Palette = null;
 		}

 		// Does not exist in the world, so a world positions don't make sense
-		public WPos Pos { get { return effectiveWorldPos; } }
-		public WVec Offset { get { return WVec.Zero; } }
-		public bool IsDecoration { get { return true; } }
+		public WPos Pos { get; }
+		public WVec Offset => WVec.Zero;
+		public bool IsDecoration => true;

-		public PaletteReference Palette { get { return palette; } }
-		public int ZOffset { get { return zOffset; } }
+		public PaletteReference Palette { get; }
+		public int ZOffset { get; }

-		public IRenderable WithPalette(PaletteReference newPalette) { return new UISpriteRenderable(sprite, effectiveWorldPos, screenPos, zOffset, newPalette, scale); }
+		public IPalettedRenderable WithPalette(PaletteReference newPalette) { return new UISpriteRenderable(sprite, Pos, screenPos, ZOffset, newPalette, scale, alpha, rotation); }
 		public IRenderable WithZOffset(int newOffset) { return this; }
-		public IRenderable OffsetBy(WVec vec) { return this; }
+		public IRenderable OffsetBy(in WVec vec) { return this; }
 		public IRenderable AsDecoration() { return this; }

 		public IFinalizedRenderable PrepareRender(WorldRenderer wr) { return this; }
 		public void Render(WorldRenderer wr)
 		{
-			Game.Renderer.SpriteRenderer.DrawSprite(sprite, screenPos, palette, scale * sprite.Size);
+			Game.Renderer.SpriteRenderer.DrawSprite(sprite, Palette, screenPos, scale, float3.Ones, alpha, rotation);
 		}

 		public void RenderDebugGeometry(WorldRenderer wr)
 		{
 			var offset = screenPos + sprite.Offset.XY;
-			Game.Renderer.RgbaColorRenderer.DrawRect(offset, offset + sprite.Size.XY, 1, Color.Red);
+			if (rotation == 0f)
+				Game.Renderer.RgbaColorRenderer.DrawRect(offset, offset + sprite.Size.XY, 1, Color.Red);
+			else
+				Game.Renderer.RgbaColorRenderer.DrawPolygon(Util.RotateQuad(offset, sprite.Size, rotation), 1, Color.Red);
 		}

 		public Rectangle ScreenBounds(WorldRenderer wr)
 		{
 			var offset = screenPos + sprite.Offset;
-			return new Rectangle((int)offset.X, (int)offset.Y, (int)sprite.Size.X, (int)sprite.Size.Y);
+			return Util.BoundingRectangle(offset, sprite.Size, rotation);
 		}
 	}
 }
--- a/OpenRA.Game/Graphics/Util.cs
+++ b/OpenRA.Game/Graphics/Util.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -20,29 +20,60 @@ namespace OpenRA.Graphics
 		// yes, our channel order is nuts.
 		static readonly int[] ChannelMasks = { 2, 1, 0, 3 };

-		public static void FastCreateQuad(Vertex[] vertices, in float3 o, Sprite r, int2 samplers, float paletteTextureIndex, int nv, in float3 size, in float3 tint)
+		public static void FastCreateQuad(Vertex[] vertices, in float3 o, Sprite r, int2 samplers, float paletteTextureIndex, int nv,
+			in float3 size, in float3 tint, float alpha, float rotation = 0f)
 		{
-			var b = new float3(o.X + size.X, o.Y, o.Z);
-			var c = new float3(o.X + size.X, o.Y + size.Y, o.Z + size.Z);
-			var d = new float3(o.X, o.Y + size.Y, o.Z + size.Z);
-			FastCreateQuad(vertices, o, b, c, d, r, samplers, paletteTextureIndex, tint, nv);
+			float3 a, b, c, d;
+
+			// Rotate sprite if rotation angle is not equal to 0
+			if (rotation != 0f)
+			{
+				var center = o + 0.5f * size;
+				var angleSin = (float)Math.Sin(-rotation);
+				var angleCos = (float)Math.Cos(-rotation);
+
+				// Rotated offset for +/- x with +/- y
+				var ra = 0.5f * new float3(
+					size.X * angleCos - size.Y * angleSin,
+					size.X * angleSin + size.Y * angleCos,
+					(size.X * angleSin + size.Y * angleCos) * size.Z / size.Y);
+
+				// Rotated offset for +/- x with -/+ y
+				var rb = 0.5f * new float3(
+					size.X * angleCos + size.Y * angleSin,
+					size.X * angleSin - size.Y * angleCos,
+					(size.X * angleSin - size.Y * angleCos) * size.Z / size.Y);
+
+				a = center - ra;
+				b = center + rb;
+				c = center + ra;
+				d = center - rb;
+			}
+			else
+			{
+				a = o;
+				b = new float3(o.X + size.X, o.Y, o.Z);
+				c = new float3(o.X + size.X, o.Y + size.Y, o.Z + size.Z);
+				d = new float3(o.X, o.Y + size.Y, o.Z + size.Z);
+			}
+
+			FastCreateQuad(vertices, a, b, c, d, r, samplers, paletteTextureIndex, tint, alpha, nv);
 		}

 		public static void FastCreateQuad(Vertex[] vertices,
 			in float3 a, in float3 b, in float3 c, in float3 d,
 			Sprite r, int2 samplers, float paletteTextureIndex,
-			in float3 tint, int nv)
+			in float3 tint, float alpha, int nv)
 		{
 			float sl = 0;
 			float st = 0;
 			float sr = 0;
 			float sb = 0;

-			// See shp.vert for documentation on the channel attribute format
+			// See combined.vert for documentation on the channel attribute format
 			var attribC = r.Channel == TextureChannel.RGBA ? 0x02 : ((byte)r.Channel) << 1 | 0x01;
 			attribC |= samplers.X << 6;
-			var ss = r as SpriteWithSecondaryData;
-			if (ss != null)
+			if (r is SpriteWithSecondaryData ss)
 			{
 				sl = ss.SecondaryLeft;
 				st = ss.SecondaryTop;
@@ -54,15 +85,15 @@ namespace OpenRA.Graphics
 			}

 			var fAttribC = (float)attribC;
-			vertices[nv] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC, tint);
-			vertices[nv + 1] = new Vertex(b, r.Right, r.Top, sr, st, paletteTextureIndex, fAttribC, tint);
-			vertices[nv + 2] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC, tint);
-			vertices[nv + 3] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC, tint);
-			vertices[nv + 4] = new Vertex(d, r.Left, r.Bottom, sl, sb, paletteTextureIndex, fAttribC, tint);
-			vertices[nv + 5] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC, tint);
+			vertices[nv] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC, tint, alpha);
+			vertices[nv + 1] = new Vertex(b, r.Right, r.Top, sr, st, paletteTextureIndex, fAttribC, tint, alpha);
+			vertices[nv + 2] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC, tint, alpha);
+			vertices[nv + 3] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC, tint, alpha);
+			vertices[nv + 4] = new Vertex(d, r.Left, r.Bottom, sl, sb, paletteTextureIndex, fAttribC, tint, alpha);
+			vertices[nv + 5] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC, tint, alpha);
 		}

-		public static void FastCopyIntoChannel(Sprite dest, byte[] src)
+		public static void FastCopyIntoChannel(Sprite dest, byte[] src, SpriteFrameType srcType)
 		{
 			var destData = dest.Sheet.GetData();
 			var width = dest.Bounds.Width;
@@ -85,12 +116,34 @@ namespace OpenRA.Graphics
 						{
 							for (var i = 0; i < width; i++)
 							{
-								var r = src[k++];
-								var g = src[k++];
-								var b = src[k++];
-								var a = src[k++];
-								var cc = Color.FromArgb(a, r, g, b);
+								byte r, g, b, a;
+								switch (srcType)
+								{
+									case SpriteFrameType.Bgra32:
+									case SpriteFrameType.Bgr24:
+									{
+										b = src[k++];
+										g = src[k++];
+										r = src[k++];
+										a = srcType == SpriteFrameType.Bgra32 ? src[k++] : (byte)255;
+										break;
+									}

+									case SpriteFrameType.Rgba32:
+									case SpriteFrameType.Rgb24:
+									{
+										r = src[k++];
+										g = src[k++];
+										b = src[k++];
+										a = srcType == SpriteFrameType.Rgba32 ? src[k++] : (byte)255;
+										break;
+									}
+
+									default:
+										throw new InvalidOperationException($"Unknown SpriteFrameType {srcType}");
+								}
+
+								var cc = Color.FromArgb(a, r, g, b);
 								data[(y + j) * destStride + x + i] = PremultiplyAlpha(cc).ToArgb();
 							}
 						}
@@ -139,16 +192,29 @@ namespace OpenRA.Graphics
 						for (var i = 0; i < width; i++)
 						{
 							Color cc;
-							if (src.Palette == null)
+							switch (src.Type)
 							{
-								var r = src.Data[k++];
-								var g = src.Data[k++];
-								var b = src.Data[k++];
-								var a = src.Data[k++];
-								cc = Color.FromArgb(a, r, g, b);
+								case SpriteFrameType.Indexed8:
+								{
+									cc = src.Palette[src.Data[k++]];
+									break;
+								}
+
+								case SpriteFrameType.Rgba32:
+								case SpriteFrameType.Rgb24:
+								{
+									var r = src.Data[k++];
+									var g = src.Data[k++];
+									var b = src.Data[k++];
+									var a = src.Type == SpriteFrameType.Rgba32 ? src.Data[k++] : (byte)255;
+									cc = Color.FromArgb(a, r, g, b);
+									break;
+								}
+
+								// Pngs don't support BGR[A], so no need to include them here
+								default:
+									throw new InvalidOperationException($"Unknown SpriteFrameType {src.Type}");
 							}
-							else
-								cc = src.Palette[src.Data[k++]];

 							data[(y + j) * destStride + x + i] = PremultiplyAlpha(cc).ToArgb();
 						}
@@ -157,6 +223,69 @@ namespace OpenRA.Graphics
 			}
 		}

+		/// <summary>Rotates a quad about its center in the x-y plane.</summary>
+		/// <param name="tl">The top left vertex of the quad.</param>
+		/// <param name="size">A float3 containing the X, Y, and Z lengths of the quad.</param>
+		/// <param name="rotation">The number of radians to rotate by.</param>
+		/// <returns>An array of four vertices representing the rotated quad (top-left, top-right, bottom-right, bottom-left).</returns>
+		public static float3[] RotateQuad(float3 tl, float3 size, float rotation)
+		{
+			var center = tl + 0.5f * size;
+			var angleSin = (float)Math.Sin(-rotation);
+			var angleCos = (float)Math.Cos(-rotation);
+
+			// Rotated offset for +/- x with +/- y
+			var ra = 0.5f * new float3(
+				size.X * angleCos - size.Y * angleSin,
+				size.X * angleSin + size.Y * angleCos,
+				(size.X * angleSin + size.Y * angleCos) * size.Z / size.Y);
+
+			// Rotated offset for +/- x with -/+ y
+			var rb = 0.5f * new float3(
+				size.X * angleCos + size.Y * angleSin,
+				size.X * angleSin - size.Y * angleCos,
+				(size.X * angleSin - size.Y * angleCos) * size.Z / size.Y);
+
+			return new float3[]
+			{
+				center - ra,
+				center + rb,
+				center + ra,
+				center - rb
+			};
+		}
+
+		/// <summary>
+		/// Returns the bounds of an object. Used for determining which objects need to be rendered on screen, and which do not.
+		/// </summary>
+		/// <param name="offset">The top left vertex of the object.</param>
+		/// <param name="size">A float 3 containing the X, Y, and Z lengths of the object.</param>
+		/// <param name="rotation">The angle to rotate the object by (use 0f if there is no rotation).</param>
+		public static Rectangle BoundingRectangle(float3 offset, float3 size, float rotation)
+		{
+			if (rotation == 0f)
+				return new Rectangle((int)offset.X, (int)offset.Y, (int)size.X, (int)size.Y);
+
+			var rotatedQuad = RotateQuad(offset, size, rotation);
+			var minX = rotatedQuad[0].X;
+			var maxX = rotatedQuad[0].X;
+			var minY = rotatedQuad[0].Y;
+			var maxY = rotatedQuad[0].Y;
+			for (var i = 1; i < rotatedQuad.Length; i++)
+			{
+				minX = Math.Min(rotatedQuad[i].X, minX);
+				maxX = Math.Max(rotatedQuad[i].X, maxX);
+				minY = Math.Min(rotatedQuad[i].Y, minY);
+				maxY = Math.Max(rotatedQuad[i].Y, maxY);
+			}
+
+			return new Rectangle(
+				(int)minX,
+				(int)minY,
+				(int)Math.Ceiling(maxX) - (int)minX,
+				(int)Math.Ceiling(maxY) - (int)minY);
+		}
+
 		public static Color PremultiplyAlpha(Color c)
 		{
 			if (c.A == byte.MaxValue)
--- a/OpenRA.Game/Graphics/Vertex.cs
+++ b/OpenRA.Game/Graphics/Vertex.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -14,7 +14,7 @@ using System.Runtime.InteropServices;
 namespace OpenRA.Graphics
 {
 	[StructLayout(LayoutKind.Sequential)]
-	public struct Vertex
+	public readonly struct Vertex
 	{
 		// 3d position
 		public readonly float X, Y, Z;
@@ -26,24 +26,24 @@ namespace OpenRA.Graphics
 		public readonly float P, C;

 		// Color tint
-		public readonly float R, G, B;
+		public readonly float R, G, B, A;

 		public Vertex(in float3 xyz, float s, float t, float u, float v, float p, float c)
-			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c, float3.Ones) { }
+			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c, float3.Ones, 1f) { }

-		public Vertex(in float3 xyz, float s, float t, float u, float v, float p, float c, in float3 tint)
-			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c, tint.X, tint.Y, tint.Z) { }
+		public Vertex(in float3 xyz, float s, float t, float u, float v, float p, float c, in float3 tint, float a)
+			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c, tint.X, tint.Y, tint.Z, a) { }

-		public Vertex(float x, float y, float z, float s, float t, float u, float v, float p, float c, in float3 tint)
-			: this(x, y, z, s, t, u, v, p, c, tint.X, tint.Y, tint.Z) { }
+		public Vertex(float x, float y, float z, float s, float t, float u, float v, float p, float c, in float3 tint, float a)
+			: this(x, y, z, s, t, u, v, p, c, tint.X, tint.Y, tint.Z, a) { }

-		public Vertex(float x, float y, float z, float s, float t, float u, float v, float p, float c, float r, float g, float b)
+		public Vertex(float x, float y, float z, float s, float t, float u, float v, float p, float c, float r, float g, float b, float a)
 		{
 			X = x; Y = y; Z = z;
 			S = s; T = t;
 			U = u; V = v;
 			P = p; C = c;
-			R = r; G = g; B = b;
+			R = r; G = g; B = b; A = a;
 		}
 	}
 }
--- a/OpenRA.Game/Graphics/Video.cs
+++ b/OpenRA.Game/Graphics/Video.cs
@@ -0,0 +1,36 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+namespace OpenRA.Video
+{
+	public interface IVideo
+	{
+		ushort FrameCount { get; }
+		byte Framerate { get; }
+		ushort Width { get; }
+		ushort Height { get; }
+
+		/// <summary>
+		/// Current frame color data in 32-bit BGRA.
+		/// </summary>
+		byte[] CurrentFrameData { get; }
+		int CurrentFrameIndex { get; }
+		void AdvanceFrame();
+
+		bool HasAudio { get; }
+		byte[] AudioData { get; }
+		int AudioChannels { get; }
+		int SampleBits { get; }
+		int SampleRate { get; }
+
+		void Reset();
+	}
+}
--- a/OpenRA.Game/Graphics/VideoLoader.cs
+++ b/OpenRA.Game/Graphics/VideoLoader.cs
@@ -0,0 +1,32 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.IO;
+
+namespace OpenRA.Video
+{
+	public interface IVideoLoader
+	{
+		bool TryParseVideo(Stream s, bool useFramePadding, out IVideo video);
+	}
+
+	public static class VideoLoader
+	{
+		public static IVideo GetVideo(Stream stream, bool useFramePadding, IVideoLoader[] loaders)
+		{
+			foreach (var loader in loaders)
+				if (loader.TryParseVideo(stream, useFramePadding, out var video))
+					return video;
+
+			return null;
+		}
+	}
+}
--- a/OpenRA.Game/Graphics/Viewport.cs
+++ b/OpenRA.Game/Graphics/Viewport.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -51,11 +51,11 @@ namespace OpenRA.Graphics
 		// Viewport geometry (world-px)
 		public int2 CenterLocation { get; private set; }

-		public WPos CenterPosition { get { return worldRenderer.ProjectedPosition(CenterLocation); } }
+		public WPos CenterPosition => worldRenderer.ProjectedPosition(CenterLocation);

-		public Rectangle Rectangle { get { return new Rectangle(TopLeft, new Size(viewportSize.X, viewportSize.Y)); } }
-		public int2 TopLeft { get { return CenterLocation - viewportSize / 2; } }
-		public int2 BottomRight { get { return CenterLocation + viewportSize / 2; } }
+		public Rectangle Rectangle => new(TopLeft, new Size(viewportSize.X, viewportSize.Y));
+		public int2 TopLeft => CenterLocation - viewportSize / 2;
+		public int2 BottomRight => CenterLocation + viewportSize / 2;
 		int2 viewportSize;
 		ProjectedCellRegion cells;
 		bool cellsDirty = true;
@@ -66,19 +66,13 @@ namespace OpenRA.Graphics
 		WorldViewport lastViewportDistance;

 		float zoom = 1f;
-		float minZoom = 1f;
-		float maxZoom = 2f;
-
 		bool unlockMinZoom;
 		float unlockedMinZoomScale;
 		float unlockedMinZoom = 1f;

 		public float Zoom
 		{
-			get
-			{
-				return zoom;
-			}
+			get => zoom;

 			private set
 			{
@@ -89,12 +83,13 @@ namespace OpenRA.Graphics
 			}
 		}

-		public float MinZoom { get { return minZoom; } }
+		public float MinZoom { get; private set; } = 1f;
+		public float MaxZoom { get; private set; } = 2f;

 		public void AdjustZoom(float dz)
 		{
 			// Exponential ensures that equal positive and negative steps have the same effect
-			Zoom = (zoom * (float)Math.Exp(dz)).Clamp(unlockMinZoom ? unlockedMinZoom : minZoom, maxZoom);
+			Zoom = (zoom * (float)Math.Exp(dz)).Clamp(unlockMinZoom ? unlockedMinZoom : MinZoom, MaxZoom);
 		}

 		public void AdjustZoom(float dz, int2 center)
@@ -108,10 +103,10 @@ namespace OpenRA.Graphics
 		public void ToggleZoom()
 		{
 			// Unlocked zooms always reset to the default zoom
-			if (zoom < minZoom)
-				Zoom = minZoom;
+			if (zoom < MinZoom)
+				Zoom = MinZoom;
 			else
-				Zoom = zoom > minZoom ? minZoom : maxZoom;
+				Zoom = zoom > MinZoom ? MinZoom : MaxZoom;
 		}

 		public void UnlockMinimumZoom(float scale)
@@ -124,23 +119,6 @@ namespace OpenRA.Graphics
 		public static long LastMoveRunTime = 0;
 		public static int2 LastMousePos;

-		float ClosestTo(float[] collection, float target)
-		{
-			var closestValue = collection.First();
-			var subtractResult = Math.Abs(closestValue - target);
-
-			foreach (var element in collection)
-			{
-				if (Math.Abs(element - target) < subtractResult)
-				{
-					subtractResult = Math.Abs(element - target);
-					closestValue = element;
-				}
-			}
-
-			return closestValue;
-		}
-
 		public ScrollDirection GetBlockedDirections()
 		{
 			var ret = ScrollDirection.None;
@@ -194,7 +172,7 @@ namespace OpenRA.Graphics
 				UpdateViewportZooms();
 		}

-		float CalculateMinimumZoom(float minHeight, float maxHeight)
+		static float CalculateMinimumZoom(float minHeight, float maxHeight)
 		{
 			var h = Game.Renderer.NativeResolution.Height;

@@ -230,31 +208,34 @@ namespace OpenRA.Graphics

 			var vd = graphicSettings.ViewportDistance;
 			if (viewportSizes.AllowNativeZoom && vd == WorldViewport.Native)
-				minZoom = 1;
+				MinZoom = viewportSizes.DefaultScale;
 			else
 			{
 				var range = viewportSizes.GetSizeRange(vd);
-				minZoom = CalculateMinimumZoom(range.X, range.Y);
+				MinZoom = CalculateMinimumZoom(range.X, range.Y) * viewportSizes.DefaultScale;
 			}

-			maxZoom = Math.Min(minZoom * viewportSizes.MaxZoomScale, Game.Renderer.NativeResolution.Height * 1f / viewportSizes.MaxZoomWindowHeight);
+			MaxZoom = Math.Min(MinZoom * viewportSizes.MaxZoomScale, Game.Renderer.NativeResolution.Height * viewportSizes.DefaultScale / viewportSizes.MaxZoomWindowHeight);

 			if (unlockMinZoom)
 			{
-				// Specators and the map editor support zooming out by an extra factor of two.
+				// Spectators and the map editor support zooming out by an extra factor of two.
 				// TODO: Allow zooming out until the full map is visible
 				// We need to improve our viewport scroll handling to center the map as we zoom out
 				// before this will work well enough to enable
-				unlockedMinZoom = minZoom * unlockedMinZoomScale;
+				unlockedMinZoom = MinZoom * unlockedMinZoomScale;
 			}

 			if (resetCurrentZoom)
-				Zoom = minZoom;
+				Zoom = MinZoom;
 			else
-				Zoom = Zoom.Clamp(minZoom, maxZoom);
+				Zoom = Zoom.Clamp(MinZoom, MaxZoom);
+
+			var maxSize = 1f / (unlockMinZoom ? unlockedMinZoom : MinZoom) * new float2(Game.Renderer.NativeResolution);
+			Game.Renderer.SetMaximumViewportSize(new Size((int)maxSize.X, (int)maxSize.Y));

 			foreach (var t in worldRenderer.World.WorldActor.TraitsImplementing<INotifyViewportZoomExtentsChanged>())
-				t.ViewportZoomExtentsChanged(minZoom, maxZoom);
+				t.ViewportZoomExtentsChanged(MinZoom, MaxZoom);
 		}

 		public CPos ViewToWorld(int2 view)
@@ -297,7 +278,7 @@ namespace OpenRA.Graphics
 			return worldRenderer.World.Map.CellContaining(worldRenderer.ProjectedPosition(ViewToWorldPx(view)));
 		}

-		/// <summary> Returns an unfiltered list of all cells that could potentially contain the mouse cursor</summary>
+		/// <summary>Returns an unfiltered list of all cells that could potentially contain the mouse cursor.</summary>
 		IEnumerable<MPos> CandidateMouseoverCells(int2 world)
 		{
 			var map = worldRenderer.World.Map;
@@ -313,8 +294,8 @@ namespace OpenRA.Graphics
 		}

 		public int2 ViewToWorldPx(int2 view) { return (graphicSettings.UIScale / Zoom * view.ToFloat2()).ToInt2() + TopLeft; }
-		public int2 WorldToViewPx(int2 world) { return ((Zoom / graphicSettings.UIScale) * (world - TopLeft).ToFloat2()).ToInt2(); }
-		public int2 WorldToViewPx(in float3 world) { return ((Zoom / graphicSettings.UIScale) * (world - TopLeft).XY).ToInt2(); }
+		public int2 WorldToViewPx(int2 world) { return (Zoom / graphicSettings.UIScale * (world - TopLeft).ToFloat2()).ToInt2(); }
+		public int2 WorldToViewPx(in float3 world) { return (Zoom / graphicSettings.UIScale * (world - TopLeft).XY).ToInt2(); }

 		public void Center(IEnumerable<Actor> actors)
 		{
--- a/OpenRA.Game/Graphics/WorldRenderer.cs
+++ b/OpenRA.Game/Graphics/WorldRenderer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -21,38 +21,35 @@ namespace OpenRA.Graphics
 	public sealed class WorldRenderer : IDisposable
 	{
 		public static readonly Func<IRenderable, int> RenderableZPositionComparisonKey =
-			r => ZPosition(r.Pos, r.ZOffset);
+			r => r.Pos.Y + r.Pos.Z + r.ZOffset;

 		public readonly Size TileSize;
 		public readonly int TileScale;
 		public readonly World World;
-		public readonly Theater Theater;
-		public Viewport Viewport { get; private set; }
+		public Viewport Viewport { get; }
 		public readonly ITerrainLighting TerrainLighting;

 		public event Action PaletteInvalidated = null;

-		readonly HashSet<Actor> onScreenActors = new HashSet<Actor>();
-		readonly HardwarePalette palette = new HardwarePalette();
-		readonly Dictionary<string, PaletteReference> palettes = new Dictionary<string, PaletteReference>();
+		readonly HashSet<Actor> onScreenActors = new();
+		readonly HardwarePalette palette = new();
+		readonly Dictionary<string, PaletteReference> palettes = new();
 		readonly IRenderTerrain terrainRenderer;
 		readonly Lazy<DebugVisualizations> debugVis;
 		readonly Func<string, PaletteReference> createPaletteReference;
 		readonly bool enableDepthBuffer;

-		readonly List<IFinalizedRenderable> preparedRenderables = new List<IFinalizedRenderable>();
-		readonly List<IFinalizedRenderable> preparedOverlayRenderables = new List<IFinalizedRenderable>();
-		readonly List<IFinalizedRenderable> preparedAnnotationRenderables = new List<IFinalizedRenderable>();
+		readonly List<IFinalizedRenderable> preparedRenderables = new();
+		readonly List<IFinalizedRenderable> preparedOverlayRenderables = new();
+		readonly List<IFinalizedRenderable> preparedAnnotationRenderables = new();

-		readonly List<IRenderable> renderablesBuffer = new List<IRenderable>();
-
-		bool lastDepthPreviewEnabled;
+		readonly List<IRenderable> renderablesBuffer = new();

 		internal WorldRenderer(ModData modData, World world)
 		{
 			World = world;
 			TileSize = World.Map.Grid.TileSize;
-			TileScale = World.Map.Grid.Type == MapGridType.RectangularIsometric ? 1448 : 1024;
+			TileScale = World.Map.Grid.TileScale;
 			Viewport = new Viewport(this, world.Map);

 			createPaletteReference = CreatePaletteReference;
@@ -68,7 +65,6 @@ namespace OpenRA.Graphics

 			palette.Initialize();

-			Theater = new Theater(world.Map.Rules.TileSet);
 			TerrainLighting = world.WorldActor.TraitOrDefault<ITerrainLighting>();
 			terrainRenderer = world.WorldActor.TraitOrDefault<IRenderTerrain>();

@@ -87,7 +83,13 @@ namespace OpenRA.Graphics
 			return new PaletteReference(name, palette.GetPaletteIndex(name), pal, palette);
 		}

-		public PaletteReference Palette(string name) { return palettes.GetOrAdd(name, createPaletteReference); }
+		public PaletteReference Palette(string name)
+		{
+			// HACK: This is working around the fact that palettes are defined on traits rather than sequences
+			// and can be removed once this has been fixed.
+			return string.IsNullOrEmpty(name) ? null : palettes.GetOrAdd(name, createPaletteReference);
+		}
+
 		public void AddPalette(string name, ImmutablePalette pal, bool allowModifiers = false, bool allowOverwrite = false)
 		{
 			if (allowOverwrite && palette.Contains(name))
@@ -107,8 +109,13 @@ namespace OpenRA.Graphics
 			palette.ReplacePalette(name, pal);

 			// Update cached PlayerReference if one exists
-			if (palettes.ContainsKey(name))
-				palettes[name].Palette = pal;
+			if (palettes.TryGetValue(name, out var paletteReference))
+				paletteReference.Palette = pal;
+		}
+
+		public void SetPaletteColorShift(string name, float hueOffset, float satOffset, float valueModifier, float minHue, float maxHue)
+		{
+			palette.SetColorShift(name, hueOffset, satOffset, valueModifier, minHue, maxHue);
 		}

 		// PERF: Avoid LINQ.
@@ -144,14 +151,14 @@ namespace OpenRA.Graphics
 		// PERF: Avoid LINQ.
 		void GenerateOverlayRenderables()
 		{
-			foreach (var a in World.ActorsWithTrait<IRenderAboveShroud>())
+			World.ApplyToActorsWithTrait<IRenderAboveShroud>((actor, trait) =>
 			{
-				if (!a.Actor.IsInWorld || a.Actor.Disposed || (a.Trait.SpatiallyPartitionable && !onScreenActors.Contains(a.Actor)))
-					continue;
+				if (!actor.IsInWorld || actor.Disposed || (trait.SpatiallyPartitionable && !onScreenActors.Contains(actor)))
+					return;

-				foreach (var renderable in a.Trait.RenderAboveShroud(a.Actor, this))
+				foreach (var renderable in trait.RenderAboveShroud(actor, this))
 					preparedOverlayRenderables.Add(renderable.PrepareRender(this));
-			}
+			});

 			foreach (var a in World.Selection.Actors)
 			{
@@ -170,8 +177,7 @@ namespace OpenRA.Graphics

 			foreach (var e in World.Effects)
 			{
-				var ea = e as IEffectAboveShroud;
-				if (ea == null)
+				if (e is not IEffectAboveShroud ea)
 					continue;

 				foreach (var renderable in ea.RenderAboveShroud(this))
@@ -186,14 +192,14 @@ namespace OpenRA.Graphics
 		// PERF: Avoid LINQ.
 		void GenerateAnnotationRenderables()
 		{
-			foreach (var a in World.ActorsWithTrait<IRenderAnnotations>())
+			World.ApplyToActorsWithTrait<IRenderAnnotations>((actor, trait) =>
 			{
-				if (!a.Actor.IsInWorld || a.Actor.Disposed || (a.Trait.SpatiallyPartitionable && !onScreenActors.Contains(a.Actor)))
-					continue;
+				if (!actor.IsInWorld || actor.Disposed || (trait.SpatiallyPartitionable && !onScreenActors.Contains(actor)))
+					return;

-				foreach (var renderAnnotation in a.Trait.RenderAnnotations(a.Actor, this))
+				foreach (var renderAnnotation in trait.RenderAnnotations(actor, this))
 					preparedAnnotationRenderables.Add(renderAnnotation.PrepareRender(this));
-			}
+			});

 			foreach (var a in World.Selection.Actors)
 			{
@@ -212,8 +218,7 @@ namespace OpenRA.Graphics

 			foreach (var e in World.Effects)
 			{
-				var ea = e as IEffectAnnotation;
-				if (ea == null)
+				if (e is not IEffectAnnotation ea)
 					continue;

 				foreach (var renderAnnotation in ea.RenderAnnotation(this))
@@ -247,11 +252,7 @@ namespace OpenRA.Graphics
 			if (World.WorldActor.Disposed)
 				return;

-			if (debugVis.Value != null && lastDepthPreviewEnabled != debugVis.Value.DepthBuffer)
-			{
-				lastDepthPreviewEnabled = debugVis.Value.DepthBuffer;
-				Game.Renderer.WorldSpriteRenderer.SetDepthPreviewEnabled(lastDepthPreviewEnabled);
-			}
+			debugVis.Value?.UpdateDepthBuffer();

 			var bounds = Viewport.GetScissorBounds(World.Type != WorldType.Editor);
 			Game.Renderer.EnableScissor(bounds);
@@ -269,15 +270,16 @@ namespace OpenRA.Graphics
 			if (enableDepthBuffer)
 				Game.Renderer.ClearDepthBuffer();

-			foreach (var a in World.ActorsWithTrait<IRenderAboveWorld>())
-				if (a.Actor.IsInWorld && !a.Actor.Disposed)
-					a.Trait.RenderAboveWorld(a.Actor, this);
+			World.ApplyToActorsWithTrait<IRenderAboveWorld>((actor, trait) =>
+			{
+				if (actor.IsInWorld && !actor.Disposed)
+					trait.RenderAboveWorld(actor, this);
+			});

 			if (enableDepthBuffer)
 				Game.Renderer.ClearDepthBuffer();

-			foreach (var a in World.ActorsWithTrait<IRenderShroud>())
-				a.Trait.RenderShroud(this);
+			World.ApplyToActorsWithTrait<IRenderShroud>((actor, trait) => trait.RenderShroud(this));

 			if (enableDepthBuffer)
 				Game.Renderer.Context.DisableDepthBuffer();
@@ -356,7 +358,13 @@ namespace OpenRA.Graphics

 		public float3 Screen3DPosition(WPos pos)
 		{
-			var z = ZPosition(pos, 0) * (float)TileSize.Height / TileScale;
+			// The projection from world coordinates to screen coordinates has
+			// a non-obvious relationship between the y and z coordinates:
+			// * A flat surface with constant y (e.g. a vertical wall) in world coordinates
+			//   transforms into a flat surface with constant z (depth) in screen coordinates.
+			// * Increasing the world y coordinate increases screen y and z coordinates equally.
+			// * Increases the world z coordinate decreases screen y but doesn't change screen z.
+			var z = pos.Y * (float)TileSize.Height / TileScale;
 			return new float3((float)TileSize.Width * pos.X / TileScale, (float)TileSize.Height * (pos.Y - pos.Z) / TileScale, z);
 		}

@@ -375,7 +383,7 @@ namespace OpenRA.Graphics
 		}

 		// For scaling vectors to pixel sizes in the model renderer
-		public float3 ScreenVectorComponents(WVec vec)
+		public float3 ScreenVectorComponents(in WVec vec)
 		{
 			return new float3(
 				(float)TileSize.Width * vec.X / TileScale,
@@ -384,29 +392,19 @@ namespace OpenRA.Graphics
 		}

 		// For scaling vectors to pixel sizes in the model renderer
-		public float[] ScreenVector(WVec vec)
+		public float[] ScreenVector(in WVec vec)
 		{
 			var xyz = ScreenVectorComponents(vec);
 			return new[] { xyz.X, xyz.Y, xyz.Z, 1f };
 		}

-		public int2 ScreenPxOffset(WVec vec)
+		public int2 ScreenPxOffset(in WVec vec)
 		{
 			// Round to nearest pixel
 			var xyz = ScreenVectorComponents(vec);
 			return new int2((int)Math.Round(xyz.X), (int)Math.Round(xyz.Y));
 		}

-		public float ScreenZPosition(WPos pos, int offset)
-		{
-			return ZPosition(pos, offset) * (float)TileSize.Height / TileScale;
-		}
-
-		static int ZPosition(WPos pos, int offset)
-		{
-			return pos.Y + pos.Z + offset;
-		}
-
 		/// <summary>
 		/// Returns a position in the world that is projected to the given screen position.
 		/// There are many possible world positions, and the returned value chooses the value with no elevation.
@@ -425,7 +423,6 @@ namespace OpenRA.Graphics
 			World.Dispose();

 			palette.Dispose();
-			Theater.Dispose();
 		}
 	}
 }
--- a/OpenRA.Game/HotkeyDefinition.cs
+++ b/OpenRA.Game/HotkeyDefinition.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -19,7 +19,9 @@ namespace OpenRA
 		public readonly string Name;
 		public readonly Hotkey Default = Hotkey.Invalid;
 		public readonly string Description = "";
-		public readonly HashSet<string> Types = new HashSet<string>();
+		public readonly HashSet<string> Types = new();
+		public readonly HashSet<string> Contexts = new();
+		public readonly bool Readonly = false;
 		public bool HasDuplicates { get; internal set; }

 		public HotkeyDefinition(string name, MiniYaml node)
@@ -36,6 +38,22 @@ namespace OpenRA
 			var typesNode = node.Nodes.FirstOrDefault(n => n.Key == "Types");
 			if (typesNode != null)
 				Types = FieldLoader.GetValue<HashSet<string>>("Types", typesNode.Value.Value);
+
+			var contextsNode = node.Nodes.FirstOrDefault(n => n.Key == "Contexts");
+			if (contextsNode != null)
+				Contexts = FieldLoader.GetValue<HashSet<string>>("Contexts", contextsNode.Value.Value);
+
+			var platformNode = node.Nodes.FirstOrDefault(n => n.Key == "Platform");
+			if (platformNode != null)
+			{
+				var platformOverride = platformNode.Value.Nodes.FirstOrDefault(n => n.Key == Platform.CurrentPlatform.ToString());
+				if (platformOverride != null)
+					Default = FieldLoader.GetValue<Hotkey>("value", platformOverride.Value.Value);
+			}
+
+			var readonlyNode = node.Nodes.FirstOrDefault(n => n.Key == "Readonly");
+			if (readonlyNode != null)
+				Readonly = FieldLoader.GetValue<bool>("Readonly", readonlyNode.Value.Value);
 		}
 	}
 }
--- a/OpenRA.Game/HotkeyManager.cs
+++ b/OpenRA.Game/HotkeyManager.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -18,8 +18,8 @@ namespace OpenRA
 	public sealed class HotkeyManager
 	{
 		readonly Dictionary<string, Hotkey> settings;
-		readonly Dictionary<string, HotkeyDefinition> definitions = new Dictionary<string, HotkeyDefinition>();
-		readonly Dictionary<string, Hotkey> keys = new Dictionary<string, Hotkey>();
+		readonly Dictionary<string, HotkeyDefinition> definitions = new();
+		readonly Dictionary<string, Hotkey> keys = new();

 		public HotkeyManager(IReadOnlyFileSystem fileSystem, Dictionary<string, Hotkey> settings, Manifest manifest)
 		{
@@ -35,14 +35,17 @@ namespace OpenRA

 			foreach (var kv in settings)
 			{
-				if (definitions.ContainsKey(kv.Key))
+				if (definitions.TryGetValue(kv.Key, out var definition) && !definition.Readonly)
 					keys[kv.Key] = kv.Value;
 			}

 			foreach (var hd in definitions)
-				hd.Value.HasDuplicates = GetFirstDuplicate(hd.Value.Name, this[hd.Value.Name].GetValue(), hd.Value) != null;
+				hd.Value.HasDuplicates = GetFirstDuplicate(hd.Value, this[hd.Value.Name].GetValue()) != null;
 		}

+		[System.Diagnostics.CodeAnalysis.SuppressMessage(
+			"Performance", "CA1854:Prefer the 'IDictionary.TryGetValue(TKey, out TValue)' method",
+			Justification = "Func must perform a live lookup in the collection, as the lookup value can change.")]
 		internal Func<Hotkey> GetHotkeyReference(string name)
 		{
 			// Is this a mod-defined hotkey?
@@ -61,6 +64,9 @@ namespace OpenRA
 			if (!definitions.TryGetValue(name, out var definition))
 				return;

+			if (definition.Readonly)
+				return;
+
 			keys[name] = value;
 			if (value != definition.Default)
 				settings[name] = value;
@@ -68,7 +74,7 @@ namespace OpenRA
 				settings.Remove(name);

 			var hadDuplicates = definition.HasDuplicates;
-			definition.HasDuplicates = GetFirstDuplicate(definition.Name, this[definition.Name].GetValue(), definition) != null;
+			definition.HasDuplicates = GetFirstDuplicate(definition, this[definition.Name].GetValue()) != null;

 			if (hadDuplicates || definition.HasDuplicates)
 			{
@@ -77,33 +83,30 @@ namespace OpenRA
 					if (hd.Value == definition)
 						continue;

-					hd.Value.HasDuplicates = GetFirstDuplicate(hd.Value.Name, this[hd.Value.Name].GetValue(), hd.Value) != null;
+					hd.Value.HasDuplicates = GetFirstDuplicate(hd.Value, this[hd.Value.Name].GetValue()) != null;
 				}
 			}
 		}

-		public HotkeyDefinition GetFirstDuplicate(string name, Hotkey value, HotkeyDefinition definition)
+		public HotkeyDefinition GetFirstDuplicate(HotkeyDefinition definition, Hotkey value)
 		{
+			if (definition == null)
+				return null;
+
 			foreach (var kv in keys)
 			{
-				if (kv.Key == name)
+				if (kv.Key == definition.Name)
 					continue;

-				if (kv.Value == value && definitions[kv.Key].Types.Overlaps(definition.Types))
+				if (kv.Value == value && definitions[kv.Key].Contexts.Overlaps(definition.Contexts))
 					return definitions[kv.Key];
 			}

 			return null;
 		}

-		public HotkeyReference this[string name]
-		{
-			get
-			{
-				return new HotkeyReference(GetHotkeyReference(name));
-			}
-		}
+		public HotkeyReference this[string name] => new(GetHotkeyReference(name));

-		public IEnumerable<HotkeyDefinition> Definitions { get { return definitions.Values; } }
+		public IEnumerable<HotkeyDefinition> Definitions => definitions.Values;
 	}
 }
--- a/OpenRA.Game/HttpExtension.cs
+++ b/OpenRA.Game/HttpExtension.cs
@@ -0,0 +1,63 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.IO;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace OpenRA
+{
+	public delegate void OnProgress(long total, long totalRead, int progressPercentage);
+
+	public static class HttpExtension
+	{
+		public static async Task ReadAsStreamWithProgress(this HttpResponseMessage response, Stream outputStream, OnProgress onProgress, CancellationToken token)
+		{
+			var total = response.Content.Headers.ContentLength ?? -1;
+			var canReportProgress = total > 0;
+
+#if NET5_0_OR_GREATER
+			using (var contentStream = await response.Content.ReadAsStreamAsync(token))
+#else
+			using (var contentStream = await response.Content.ReadAsStreamAsync())
+#endif
+			{
+				var totalRead = 0L;
+				var buffer = new byte[8192];
+				var hasMoreToRead = true;
+
+				do
+				{
+					var read = await contentStream.ReadAsync(buffer.AsMemory(0, buffer.Length), token);
+					if (read == 0)
+						hasMoreToRead = false;
+					else
+					{
+						await outputStream.WriteAsync(buffer.AsMemory(0, read), token);
+
+						totalRead += read;
+
+						if (canReportProgress)
+						{
+							var progressPercentage = (int)((double)totalRead / total * 100);
+							onProgress?.Invoke(total, totalRead, progressPercentage);
+						}
+					}
+				}
+				while (hasMoreToRead && !token.IsCancellationRequested);
+
+				onProgress?.Invoke(total, totalRead, 100);
+			}
+		}
+	}
+}
--- a/OpenRA.Game/IUtilityCommand.cs
+++ b/OpenRA.Game/IUtilityCommand.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -9,12 +9,41 @@
 */
 #endregion

+using System;
+using System.Reflection;
+using OpenRA.Primitives;
 using OpenRA.Traits;

 namespace OpenRA
 {
 	public class Utility
 	{
+		static readonly ConcurrentCache<Type, FieldInfo[]> TypeFields =
+			new(type => type.GetFields());
+
+		static readonly ConcurrentCache<(MemberInfo Member, Type AttributeType), bool> MemberHasAttribute =
+			new(x => Attribute.IsDefined(x.Member, x.AttributeType));
+
+		static readonly ConcurrentCache<(MemberInfo Member, Type AttributeType, bool Inherit), object[]> MemberCustomAttributes =
+			new(x => x.Member.GetCustomAttributes(x.AttributeType, x.Inherit));
+
+		public static FieldInfo[] GetFields(Type type)
+		{
+			return TypeFields[type];
+		}
+
+		public static bool HasAttribute<TAttribute>(MemberInfo member)
+			where TAttribute : Attribute
+		{
+			return MemberHasAttribute[(member, typeof(TAttribute))];
+		}
+
+		public static TAttribute[] GetCustomAttributes<TAttribute>(MemberInfo member, bool inherit)
+			where TAttribute : Attribute
+		{
+			return (TAttribute[])MemberCustomAttributes[(member, typeof(TAttribute), inherit)];
+		}
+
 		public readonly ModData ModData;
 		public readonly InstalledMods Mods;

--- a/OpenRA.Game/Input/Hotkey.cs
+++ b/OpenRA.Game/Input/Hotkey.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -13,9 +13,9 @@ using System;

 namespace OpenRA
 {
-	public struct Hotkey : IEquatable<Hotkey>
+	public readonly struct Hotkey : IEquatable<Hotkey>
 	{
-		public static Hotkey Invalid = new Hotkey(Keycode.UNKNOWN, Modifiers.None);
+		public static Hotkey Invalid = new(Keycode.UNKNOWN, Modifiers.None);
 		public bool IsValid()
 		{
 			return Key != Keycode.UNKNOWN;
@@ -42,7 +42,7 @@ namespace OpenRA
 			var mods = Modifiers.None;
 			if (parts.Length >= 2)
 			{
-				var modString = s.Substring(s.IndexOf(' '));
+				var modString = s[s.IndexOf(' ')..];
 				if (!Enum<Modifiers>.TryParse(modString, true, out mods))
 					return false;
 			}
@@ -81,11 +81,10 @@ namespace OpenRA

 		public override bool Equals(object obj)
 		{
-			var o = obj as Hotkey?;
-			return o != null && o == this;
+			return obj is Hotkey o && (Hotkey?)o == this;
 		}

-		public override string ToString() { return "{0} {1}".F(Key, Modifiers.ToString("F")); }
+		public override string ToString() { return $"{Key} {Modifiers:F}"; }

 		public string DisplayString()
 		{
--- a/OpenRA.Game/Input/HotkeyReference.cs
+++ b/OpenRA.Game/Input/HotkeyReference.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -14,7 +14,7 @@ using System;
 namespace OpenRA
 {
 	/// <summary>
-	/// A reference to either a named hotkey (defined in the game settings) or a statically assigned hotkey
+	/// A reference to either a named hotkey (defined in the game settings) or a statically assigned hotkey.
 	/// </summary>
 	public class HotkeyReference
 	{
--- a/OpenRA.Game/Input/IInputHandler.cs
+++ b/OpenRA.Game/Input/IInputHandler.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
--- a/OpenRA.Game/Input/InputHandler.cs
+++ b/OpenRA.Game/Input/InputHandler.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -37,36 +37,24 @@ namespace OpenRA

 		public void OnKeyInput(KeyInput input)
 		{
-			Sync.RunUnsynced(Game.Settings.Debug.SyncCheckUnsyncedCode, world, () => Ui.HandleKeyPress(input));
+			Sync.RunUnsynced(world, () => Ui.HandleKeyPress(input));
 		}

 		public void OnTextInput(string text)
 		{
-			Sync.RunUnsynced(Game.Settings.Debug.SyncCheckUnsyncedCode, world, () => Ui.HandleTextInput(text));
+			Sync.RunUnsynced(world, () => Ui.HandleTextInput(text));
 		}

 		public void OnMouseInput(MouseInput input)
 		{
-			Sync.RunUnsynced(Game.Settings.Debug.SyncCheckUnsyncedCode, world, () => Ui.HandleInput(input));
+			Sync.RunUnsynced(world, () => Ui.HandleInput(input));
 		}
 	}

 	public class MouseButtonPreference
 	{
-		public MouseButton Action
-		{
-			get
-			{
-				return Game.Settings.Game.UseClassicMouseStyle ? MouseButton.Left : MouseButton.Right;
-			}
-		}
+		public MouseButton Action => Game.Settings.Game.UseClassicMouseStyle ? MouseButton.Left : MouseButton.Right;

-		public MouseButton Cancel
-		{
-			get
-			{
-				return Game.Settings.Game.UseClassicMouseStyle ? MouseButton.Right : MouseButton.Left;
-			}
-		}
+		public MouseButton Cancel => Game.Settings.Game.UseClassicMouseStyle ? MouseButton.Right : MouseButton.Left;
 	}
 }
--- a/OpenRA.Game/Input/Keycode.cs
+++ b/OpenRA.Game/Input/Keycode.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -13,7 +13,8 @@ using System.Collections.Generic;

 namespace OpenRA
 {
-	// List of keycodes, duplicated from SDL 2.0.1
+	// List of keycodes. Duplicated from SDL 2.0.1, with the addition
+	// of MOUSE4 and MOUSE5.
 	public enum Keycode
 	{
 		UNKNOWN = 0,
@@ -252,11 +253,13 @@ namespace OpenRA
 		KBDILLUMUP = 280 | (1 << 30),
 		EJECT = 281 | (1 << 30),
 		SLEEP = 282 | (1 << 30),
+		MOUSE4 = 283 | (1 << 30),
+		MOUSE5 = 284 | (1 << 30)
 	}

 	public static class KeycodeExts
 	{
-		static readonly Dictionary<Keycode, string> KeyNames = new Dictionary<Keycode, string>
+		static readonly Dictionary<Keycode, string> KeyNames = new()
 		{
 			{ Keycode.UNKNOWN, "Undefined" },
 			{ Keycode.RETURN, "Return" },
@@ -494,6 +497,8 @@ namespace OpenRA
 			{ Keycode.KBDILLUMUP, "KBDIllumUp" },
 			{ Keycode.EJECT, "Eject" },
 			{ Keycode.SLEEP, "Sleep" },
+			{ Keycode.MOUSE4, "Mouse 4" },
+			{ Keycode.MOUSE5, "Mouse 5" },
 		};

 		public static string DisplayString(Keycode k)
--- a/OpenRA.Game/InstalledMods.cs
+++ b/OpenRA.Game/InstalledMods.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -15,22 +15,18 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using OpenRA.FileSystem;
-using OpenRA.Graphics;
-using OpenRA.Primitives;

 namespace OpenRA
 {
 	public class InstalledMods : IReadOnlyDictionary<string, Manifest>
 	{
 		readonly Dictionary<string, Manifest> mods;
-		readonly SheetBuilder sheetBuilder;

 		/// <summary>Initializes the collection of locally installed mods.</summary>
 		/// <param name="searchPaths">Filesystem paths to search for mod packages.</param>
 		/// <param name="explicitPaths">Filesystem paths to additional mod packages.</param>
 		public InstalledMods(IEnumerable<string> searchPaths, IEnumerable<string> explicitPaths)
 		{
-			sheetBuilder = new SheetBuilder(SheetType.BGRA, 256);
 			mods = GetInstalledMods(searchPaths, explicitPaths);
 		}

@@ -58,7 +54,7 @@ namespace OpenRA
 			return mods;
 		}

-		Manifest LoadMod(string id, string path)
+		static Manifest LoadMod(string id, string path)
 		{
 			IReadOnlyPackage package = null;
 			try
@@ -75,7 +71,7 @@ namespace OpenRA
 			}
 			catch (Exception e)
 			{
-				Log.Write("debug", "Load mod '{0}': {1}".F(path, e));
+				Log.Write("debug", $"Load mod '{path}': {e}");
 			}

 			package?.Dispose();
@@ -83,7 +79,7 @@ namespace OpenRA
 			return null;
 		}

-		Dictionary<string, Manifest> GetInstalledMods(IEnumerable<string> searchPaths, IEnumerable<string> explicitPaths)
+		static Dictionary<string, Manifest> GetInstalledMods(IEnumerable<string> searchPaths, IEnumerable<string> explicitPaths)
 		{
 			var ret = new Dictionary<string, Manifest>();
 			var candidates = GetCandidateMods(searchPaths)
@@ -99,10 +95,10 @@ namespace OpenRA
 			return ret;
 		}

-		public Manifest this[string key] { get { return mods[key]; } }
-		public int Count { get { return mods.Count; } }
-		public ICollection<string> Keys { get { return mods.Keys; } }
-		public ICollection<Manifest> Values { get { return mods.Values; } }
+		public Manifest this[string key] => mods[key];
+		public IEnumerable<string> Keys => mods.Keys;
+		public IEnumerable<Manifest> Values => mods.Values;
+		public int Count => mods.Count;
 		public bool ContainsKey(string key) { return mods.ContainsKey(key); }
 		public IEnumerator<KeyValuePair<string, Manifest>> GetEnumerator() { return mods.GetEnumerator(); }
 		public bool TryGetValue(string key, out Manifest value) { return mods.TryGetValue(key, out value); }
--- a/OpenRA.Game/LocalPlayerProfile.cs
+++ b/OpenRA.Game/LocalPlayerProfile.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -12,10 +12,10 @@
 using System;
 using System.IO;
 using System.Linq;
-using System.Net;
 using System.Security.Cryptography;
 using System.Text;
 using System.Threading.Tasks;
+using OpenRA.Support;

 namespace OpenRA
 {
@@ -24,11 +24,11 @@ namespace OpenRA
 		const int AuthKeySize = 2048;
 		public enum LinkState { Uninitialized, GeneratingKeys, Unlinked, CheckingLink, ConnectionFailed, Linked }

-		public LinkState State { get { return innerState; } }
-		public string Fingerprint { get { return innerFingerprint; } }
-		public string PublicKey { get { return innerPublicKey; } }
+		public LinkState State => innerState;
+		public string Fingerprint => innerFingerprint;
+		public string PublicKey => innerPublicKey;

-		public PlayerProfile ProfileData { get { return innerData; } }
+		public PlayerProfile ProfileData => innerData;

 		volatile LinkState innerState;
 		volatile PlayerProfile innerData;
@@ -66,8 +66,10 @@ namespace OpenRA
 			}
 			catch (Exception e)
 			{
-				Console.WriteLine("Failed to load keys: {0}", e);
-				Log.Write("debug", "Failed to load player keypair from `{0}` with exception: {1}", filePath, e);
+				Console.WriteLine("Failed to load keys:");
+				Console.WriteLine(e);
+				Log.Write("debug", $"Failed to load player keypair from `{filePath}` with exception:");
+				Log.Write("debug", e);
 			}
 		}

@@ -76,23 +78,22 @@ namespace OpenRA
 			if (State != LinkState.Unlinked && State != LinkState.Linked && State != LinkState.ConnectionFailed)
 				return;

-			Action<DownloadDataCompletedEventArgs> onQueryComplete = i =>
+			Task.Run(async () =>
 			{
 				try
 				{
-					if (i.Error != null)
-					{
-						innerState = LinkState.ConnectionFailed;
-						return;
-					}
+					var client = HttpClientFactory.Create();

-					var yaml = MiniYaml.FromString(Encoding.UTF8.GetString(i.Result)).First();
+					var httpResponseMessage = await client.GetAsync(playerDatabase.Profile + Fingerprint);
+					var result = await httpResponseMessage.Content.ReadAsStreamAsync();
+
+					var yaml = MiniYaml.FromStream(result).First();
 					if (yaml.Key == "Player")
 					{
 						innerData = FieldLoader.Load<PlayerProfile>(yaml.Value);
 						if (innerData.KeyRevoked)
 						{
-							Log.Write("debug", "Revoking key with fingerprint {0}", Fingerprint);
+							Log.Write("debug", $"Revoking key with fingerprint {Fingerprint}");
 							DeleteKeypair();
 						}
 						else
@@ -103,17 +104,17 @@ namespace OpenRA
 				}
 				catch (Exception e)
 				{
-					Log.Write("debug", "Failed to parse player data result with exception: {0}", e);
+					Log.Write("debug", "Failed to parse player data result with exception:");
+					Log.Write("debug", e);
 					innerState = LinkState.ConnectionFailed;
 				}
 				finally
 				{
 					onComplete?.Invoke();
 				}
-			};
+			});

 			innerState = LinkState.CheckingLink;
-			new Download(playerDatabase.Profile + Fingerprint, _ => { }, onQueryComplete);
 		}

 		public void GenerateKeypair()
@@ -138,8 +139,10 @@ namespace OpenRA
 				}
 				catch (Exception e)
 				{
-					Log.Write("debug", "Failed to generate keypair with exception: {1}", e);
-					Console.WriteLine("Key generation failed: {0}", e);
+					Log.Write("debug", "Failed to generate keypair with exception:");
+					Log.Write("debug", e);
+					Console.WriteLine("Key generation failed:");
+					Console.WriteLine(e);

 					innerState = LinkState.Uninitialized;
 				}
@@ -154,12 +157,14 @@ namespace OpenRA
 			}
 			catch (Exception e)
 			{
-				Log.Write("debug", "Failed to delete keypair with exception: {1}", e);
-				Console.WriteLine("Key deletion failed: {0}", e);
+				Log.Write("debug", "Failed to delete keypair with exception:");
+				Log.Write("debug", e);
+				Console.WriteLine("Key deletion failed:");
+				Console.WriteLine(e);
 			}

 			innerState = LinkState.Uninitialized;
-			parameters = default(RSAParameters);
+			parameters = default;
 			innerFingerprint = null;
 			innerData = null;
 		}
--- a/OpenRA.Game/MPos.cs
+++ b/OpenRA.Game/MPos.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -14,12 +14,12 @@ using OpenRA.Primitives;

 namespace OpenRA
 {
-	public struct MPos : IEquatable<MPos>
+	public readonly struct MPos : IEquatable<MPos>
 	{
 		public readonly int U, V;

 		public MPos(int u, int v) { U = u; V = v; }
-		public static readonly MPos Zero = new MPos(0, 0);
+		public static readonly MPos Zero = new(0, 0);

 		public static bool operator ==(MPos me, MPos other) { return me.U == other.U && me.V == other.V; }
 		public static bool operator !=(MPos me, MPos other) { return !(me == other); }
@@ -27,7 +27,7 @@ namespace OpenRA
 		public override int GetHashCode() { return U.GetHashCode() ^ V.GetHashCode(); }

 		public bool Equals(MPos other) { return other == this; }
-		public override bool Equals(object obj) { return obj is MPos && Equals((MPos)obj); }
+		public override bool Equals(object obj) { return obj is MPos uv && Equals(uv); }

 		public MPos Clamp(Rectangle r)
 		{
@@ -64,14 +64,14 @@ namespace OpenRA
 	}

 	/// <summary>
-	/// Projected map position
+	/// Projected map position.
 	/// </summary>
-	public struct PPos : IEquatable<PPos>
+	public readonly struct PPos : IEquatable<PPos>
 	{
 		public readonly int U, V;

 		public PPos(int u, int v) { U = u; V = v; }
-		public static readonly PPos Zero = new PPos(0, 0);
+		public static readonly PPos Zero = new(0, 0);

 		public static bool operator ==(PPos me, PPos other) { return me.U == other.U && me.V == other.V; }
 		public static bool operator !=(PPos me, PPos other) { return !(me == other); }
@@ -88,7 +88,7 @@ namespace OpenRA
 		public override int GetHashCode() { return U.GetHashCode() ^ V.GetHashCode(); }

 		public bool Equals(PPos other) { return other == this; }
-		public override bool Equals(object obj) { return obj is PPos && Equals((PPos)obj); }
+		public override bool Equals(object obj) { return obj is PPos puv && Equals(puv); }

 		public override string ToString() { return U + "," + V; }
 	}
--- a/OpenRA.Game/Manifest.cs
+++ b/OpenRA.Game/Manifest.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -11,6 +11,7 @@

 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
 using OpenRA.FileSystem;
@@ -20,6 +21,17 @@ namespace OpenRA
 {
 	public interface IGlobalModData { }

+	public sealed class TerrainFormat : IGlobalModData
+	{
+		public readonly string Type;
+		public readonly IReadOnlyDictionary<string, MiniYaml> Metadata;
+		public TerrainFormat(MiniYaml yaml)
+		{
+			Type = yaml.Value;
+			Metadata = new ReadOnlyDictionary<string, MiniYaml>(yaml.ToDictionary());
+		}
+	}
+
 	public sealed class SpriteSequenceFormat : IGlobalModData
 	{
 		public readonly string Type;
@@ -48,11 +60,12 @@ namespace OpenRA
 		public string Version;
 		public string Website;
 		public string WebIcon32;
+		public string WindowTitle;
 		public bool Hidden;
 	}

-	/// <summary> Describes what is to be loaded in order to run a mod. </summary>
-	public class Manifest : IDisposable
+	/// <summary>Describes what is to be loaded in order to run a mod.</summary>
+	public sealed class Manifest : IDisposable
 	{
 		public readonly string Id;
 		public readonly IReadOnlyPackage Package;
@@ -66,21 +79,23 @@ namespace OpenRA
 		public readonly IReadOnlyDictionary<string, string> Packages;
 		public readonly IReadOnlyDictionary<string, string> MapFolders;
 		public readonly MiniYaml LoadScreen;
+		public readonly string DefaultOrderGenerator;

-		public readonly string[] SoundFormats = { };
-		public readonly string[] SpriteFormats = { };
-		public readonly string[] PackageFormats = { };
+		public readonly string[] SoundFormats = Array.Empty<string>();
+		public readonly string[] SpriteFormats = Array.Empty<string>();
+		public readonly string[] PackageFormats = Array.Empty<string>();
+		public readonly string[] VideoFormats = Array.Empty<string>();

 		readonly string[] reservedModuleNames =
 		{
 			"Include", "Metadata", "Folders", "MapFolders", "Packages", "Rules",
 			"Sequences", "ModelSequences", "Cursors", "Chrome", "Assemblies", "ChromeLayout", "Weapons",
 			"Voices", "Notifications", "Music", "Translations", "TileSets", "ChromeMetrics", "Missions", "Hotkeys",
-			"ServerTraits", "LoadScreen", "SupportsMapsFrom", "SoundFormats", "SpriteFormats",
+			"ServerTraits", "LoadScreen", "DefaultOrderGenerator", "SupportsMapsFrom", "SoundFormats", "SpriteFormats", "VideoFormats",
 			"RequiresMods", "PackageFormats"
 		};

-		readonly TypeDictionary modules = new TypeDictionary();
+		readonly TypeDictionary modules = new();
 		readonly Dictionary<string, MiniYaml> yaml;

 		bool customDataLoaded;
@@ -100,7 +115,7 @@ namespace OpenRA
 				var filename = nodes[i].Value.Value;
 				var contents = package.GetStream(filename);
 				if (contents == null)
-					throw new YamlException("{0}: File `{1}` not found.".F(nodes[i].Location, filename));
+					throw new YamlException($"{nodes[i].Location}: File `{filename}` not found.");

 				nodes.RemoveAt(i);
 				nodes.InsertRange(i, MiniYaml.FromStream(contents, filename));
@@ -115,7 +130,7 @@ namespace OpenRA
 			MapFolders = YamlDictionary(yaml, "MapFolders");

 			if (yaml.TryGetValue("Packages", out var packages))
-				Packages = packages.ToDictionary(x => x.Value).AsReadOnly();
+				Packages = packages.ToDictionary(x => x.Value);

 			Rules = YamlList(yaml, "Rules");
 			Sequences = YamlList(yaml, "Sequences");
@@ -142,19 +157,25 @@ namespace OpenRA
 			// Allow inherited mods to import parent maps.
 			var compat = new List<string> { Id };

-			if (yaml.ContainsKey("SupportsMapsFrom"))
-				compat.AddRange(yaml["SupportsMapsFrom"].Value.Split(',').Select(c => c.Trim()));
+			if (yaml.TryGetValue("SupportsMapsFrom", out var entry))
+				compat.AddRange(entry.Value.Split(',').Select(c => c.Trim()));

 			MapCompatibility = compat.ToArray();

-			if (yaml.ContainsKey("PackageFormats"))
-				PackageFormats = FieldLoader.GetValue<string[]>("PackageFormats", yaml["PackageFormats"].Value);
+			if (yaml.TryGetValue("DefaultOrderGenerator", out entry))
+				DefaultOrderGenerator = entry.Value;

-			if (yaml.ContainsKey("SoundFormats"))
-				SoundFormats = FieldLoader.GetValue<string[]>("SoundFormats", yaml["SoundFormats"].Value);
+			if (yaml.TryGetValue("PackageFormats", out entry))
+				PackageFormats = FieldLoader.GetValue<string[]>("PackageFormats", entry.Value);

-			if (yaml.ContainsKey("SpriteFormats"))
-				SpriteFormats = FieldLoader.GetValue<string[]>("SpriteFormats", yaml["SpriteFormats"].Value);
+			if (yaml.TryGetValue("SoundFormats", out entry))
+				SoundFormats = FieldLoader.GetValue<string[]>("SoundFormats", entry.Value);
+
+			if (yaml.TryGetValue("SpriteFormats", out entry))
+				SpriteFormats = FieldLoader.GetValue<string[]>("SpriteFormats", entry.Value);
+
+			if (yaml.TryGetValue("VideoFormats", out entry))
+				VideoFormats = FieldLoader.GetValue<string[]>("VideoFormats", entry.Value);
 		}

 		public void LoadCustomData(ObjectCreator oc)
@@ -166,7 +187,7 @@ namespace OpenRA

 				var t = oc.FindType(kv.Key);
 				if (t == null || !typeof(IGlobalModData).IsAssignableFrom(t))
-					throw new InvalidDataException("`{0}` is not a valid mod manifest entry.".F(kv.Key));
+					throw new InvalidDataException($"`{kv.Key}` is not a valid mod manifest entry.");

 				IGlobalModData module;
 				var ctor = t.GetConstructor(new[] { typeof(MiniYaml) });
@@ -188,10 +209,10 @@ namespace OpenRA
 			customDataLoaded = true;
 		}

-		static string[] YamlList(Dictionary<string, MiniYaml> yaml, string key, bool parsePaths = false)
+		static string[] YamlList(Dictionary<string, MiniYaml> yaml, string key)
 		{
 			if (!yaml.ContainsKey(key))
-				return new string[] { };
+				return Array.Empty<string>();

 			return yaml[key].ToDictionary().Keys.ToArray();
 		}
@@ -199,10 +220,9 @@ namespace OpenRA
 		static IReadOnlyDictionary<string, string> YamlDictionary(Dictionary<string, MiniYaml> yaml, string key)
 		{
 			if (!yaml.ContainsKey(key))
-				return new ReadOnlyDictionary<string, string>();
+				return new Dictionary<string, string>();

-			var inner = yaml[key].ToDictionary(my => my.Value);
-			return new ReadOnlyDictionary<string, string>(inner);
+			return yaml[key].ToDictionary(my => my.Value);
 		}

 		public bool Contains<T>() where T : IGlobalModData
--- a/OpenRA.Game/Map/ActorInitializer.cs
+++ b/OpenRA.Game/Map/ActorInitializer.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * Copyright (c) The OpenRA Developers and Contributors
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
@@ -37,7 +37,7 @@ namespace OpenRA
 	public class ActorInitializer : IActorInitializer
 	{
 		public readonly Actor Self;
-		public World World { get { return Self.World; } }
+		public World World => Self.World;

 		internal TypeDictionary Dict;

@@ -54,7 +54,7 @@ namespace OpenRA
 			// Traits tagged with an instance name prefer inits with the same name.
 			// If a more specific init is not available, fall back to an unnamed init.
 			// If duplicate inits are defined, take the last to match standard yaml override expectations
-			if (info != null && !string.IsNullOrEmpty(info.InstanceName))
+			if (!string.IsNullOrEmpty(info?.InstanceName))
 				return inits.LastOrDefault(i => i.InstanceName == info.InstanceName) ??
 					inits.LastOrDefault(i => string.IsNullOrEmpty(i.InstanceName));

@@ -66,7 +66,7 @@ namespace OpenRA
 		{
 			var init = GetOrDefault<T>(info);
 			if (init == null)
-			    throw new InvalidOperationException("TypeDictionary does not contain instance of type `{0}`".F(typeof(T)));
+				throw new InvalidOperationException($"TypeDictionary does not contain instance of type `{typeof(T)}`");

 			return init;
 		}
@@ -140,7 +140,7 @@ namespace OpenRA

 	public abstract class ValueActorInit<T> : ActorInit
 	{
-		protected readonly T value;
+		readonly T value;

 		protected ValueActorInit(TraitInfo info, T value)
 			: base(info.InstanceName) { this.value = value; }
@@ -150,18 +150,18 @@ namespace OpenRA

 		protected ValueActorInit(T value) { this.value = value; }

-		public virtual T Value { get { return value; } }
+		public virtual T Value => value;

 		public virtual void Initialize(MiniYaml yaml)
 		{
-			Initialize((T)FieldLoader.GetValue("value", typeof(T), yaml.Value));
+			Initialize((T)FieldLoader.GetValue(nameof(value), typeof(T), yaml.Value));
 		}

 		public virtual void Initialize(T value)
 		{
-			var field = GetType().GetField("value", BindingFlags.NonPublic | BindingFlags.Instance);
-			if (field != null)
-				field.SetValue(this, value);
+			typeof(ValueActorInit<T>)
+				.GetField(nameof(value), BindingFlags.NonPublic | BindingFlags.Instance)
+				?.SetValue(this, value);
 		}

 		public override MiniYaml Save()
@@ -226,7 +226,7 @@ namespace OpenRA
 	public class OwnerInit : ActorInit, ISingleInstanceInit
 	{
 		public readonly string InternalName;
-		protected readonly Player value;
+		readonly Player value;

 		public OwnerInit(Player value)
 		{
@@ -246,16 +246,16 @@ namespace OpenRA

 		public void Initialize(MiniYaml yaml)
 		{
-			var field = GetType().GetField("InternalName", BindingFlags.Public | BindingFlags.Instance);
-			if (field != null)
-				field.SetValue(this, yaml.Value);
+			typeof(OwnerInit)
+				.GetField(nameof(InternalName), BindingFlags.Public | BindingFlags.Instance)
+				?.SetValue(this, yaml.Value);
 		}

 		public void Initialize(Player player)
 		{
-			var field = GetType().GetField("value", BindingFlags.NonPublic | BindingFlags.Instance);
-			if (field != null)
-				field.SetValue(this, player);
+			typeof(OwnerInit)
+				.GetField(nameof(value), BindingFlags.NonPublic | BindingFlags.Instance)
+				?.SetValue(this, player);
 		}

 		public override MiniYaml Save()
--- a/Show More
+++ b/Show More