Movement, Terrain & Maps

17. Locomotor System

Locomotors define how actors interact with terrain for movement.

Trait	Purpose
`Locomotor`	Base locomotor (17KB) — terrain cost tables, movement class, crushes, speed modifiers per terrain type
`SubterraneanLocomotor`	Underground movement
`SubterraneanActorLayer`	Underground layer management
`Mobile`	Actor-level movement using a locomotor
`Aircraft`	Air locomotor variant

Key Locomotor features:

Terrain cost tables — per-terrain-type movement cost
Movement classes — define pathfinding categories
Crush classes — what can be crushed
Share cells — whether units can share cells
Speed modifiers — per-terrain speed modification

18. Pathfinding System

Trait	Purpose
`PathFinder`	Main pathfinding implementation (14KB)
`HierarchicalPathFinderOverlay`	Hierarchical pathfinder debug visualization
`PathFinderOverlay`	Standard pathfinder debug

19. AI / Bot System

Bot Framework

Trait	Purpose
`ModularBot`	Modular bot framework (player trait)
`DummyBot`	Placeholder bot

Bot Modules (~12 modules)

Module	Purpose
`BaseBuilderBotModule`	Base construction AI
`BuildingRepairBotModule`	Auto-repair buildings
`CaptureManagerBotModule`	Capture neutral/enemy buildings
`HarvesterBotModule`	Resource gathering AI
`McvManagerBotModule`	MCV deployment AI
`McvExpansionManagerBotModule`	Base expansion AI
`PowerDownBotManager`	Power management AI
`ResourceMapBotModule`	Resource mapping
`SquadManagerBotModule`	Military squad management
`SupportPowerBotModule`	Superweapon usage AI
`UnitBuilderBotModule`	Unit production AI

20. Infantry System

Trait	Purpose
`WithInfantryBody`	Infantry sprite rendering with multiple sub-positions
`ScaredyCat`	Panic flee behavior
`TakeCover`	Prone/cover behavior
`TerrainModifiesDamage`	Terrain affects damage received

21. Terrain System

World Terrain Traits

Trait	Purpose
`TerrainRenderer`	Renders terrain tiles
`ResourceLayer`	Resource cell management
`ResourceRenderer`	Resource sprite rendering
`ResourceClaimLayer`	Resource claim tracking for harvesters
`EditorResourceLayer`	Editor resource placement
`SmudgeLayer`	Terrain smudges (craters, scorch marks)
`TerrainLighting`	Per-cell terrain lighting
`TerrainGeometryOverlay`	Debug geometry
`TerrainTunnel`	Terrain tunnel definition
`TerrainTunnelLayer`	Tunnel management
`CliffBackImpassabilityLayer`	Cliff impassability
`DamagedByTerrain`	Terrain damage (tiberium, etc.)
`ChangesTerrain`	Actor modifies terrain
`SeedsResource`	Creates new resources

Terrain is never just tiles — evidence from mods: Analysis of four OpenRA community mods (see research/openra-mod-architecture-analysis.md and research/openra-ra2-mod-architecture.md) reveals that terrain is one of the deepest extension points:

RA2 radiation: World-level TintedCellsLayer — sparse Dictionary<CPos, TintedCell> with configurable decay (linear, logarithmic, half-life). Radiation isn’t a visual effect; it’s a persistent terrain overlay that damages units standing in it. IC needs a WorldLayer abstraction for similar persistent cell-level state.
OpenHV floods: LaysTerrain trait — actors can permanently transform terrain type at runtime (e.g., flooding a valley changes passability and visual tiles). This breaks the assumption that terrain is static after map load.
OpenSA plant growth: Living terrain that spreads autonomously. SpreadsCondition creates expanding zones that modify pathability and visual appearance over time.
OpenKrush oil patches: Entirely different resource terrain model — fixed oil positions (not harvestable ore fields), per-patch depletion, no regrowth.

IC’s terrain system must support runtime terrain modification, world-level cell layers (for radiation, weather effects, etc.), and game-module-defined resource models — not just the RA1 ore/gem model.

Tile Sets (RA mod example)

snow — Snow terrain
interior — Interior/building tiles
temperat — Temperate terrain
desert — Desert terrain

22. Map System

Map Traits

Trait	Purpose
`MapOptions`	Game speed, tech level, starting cash, fog/shroud toggles, short game
`MapStartingLocations`	Spawn point placement
`MapStartingUnits`	Starting unit set per faction
`MapBuildRadius`	Initial build radius rules
`MapCreeps`	Enable/disable ambient wildlife
`MissionData`	Mission briefing, objectives
`CreateMapPlayers`	Initial player creation
`SpawnMapActors`	Spawn pre-placed map actors
`SpawnStartingUnits`	Spawn starting units at locations

Map Generation

Trait	Purpose
`ClassicMapGenerator`	Procedural map generation (38KB)
`ClearMapGenerator`	Empty/clear map generation

Actor Spawn

Trait	Purpose
`ActorSpawnManager`	Manages ambient actor spawning
`ActorSpawner`	Spawn point for spawned actors

23. Map Editor System

Editor World Traits

Trait	Purpose
`EditorActionManager`	Undo/redo action management
`EditorActorLayer`	Manages placed actors in editor (15KB)
`EditorActorPreview`	Actor preview rendering in editor
`EditorCursorLayer`	Editor cursor management
`EditorResourceLayer`	Resource painting
`MarkerLayerOverlay`	Marker layer visualization
`TilingPathTool`	Path/road tiling tool (14KB)

Editor Widgets

Widget	Purpose
`EditorViewportControllerWidget`	Editor viewport input handling

Editor/ subdirectory with editor-specific UI logic files

Iron Curtain — Design Documentation