Type Alias: FeatureSlot

type FeatureSlot = 
  | "animator"
  | "physics2D"
  | "uiActions"
  | "uiControls"
  | "physics2DPose"
  | "uiTransitions"
  | "uiTransitionsRestore"
  | "particles2DSimulation"
  | "inputField"
  | "particles2DRender";

An optional part of the engine — particles, 2D physics, UI controls, … — that a build carries only when it's asked for (EngineOptions.features). The Engine never imports one: it keeps named slots in its system order and each feature fills its own, so leaving a feature out removes its systems, its components and whatever they import from the bundle (the package is side-effect-free; a component module is included only when something names its class). Where a feature's systems go in the engine's order (Engine's constructor lists them in place).