Ctx

Every system receives (world, ctx). The ctx exposes the kernel resources:

type Ctx = {
  time: Time;
  rng: Rng;
  res: Resources;
  input: Input;
  debug: Debug;
  palette: Palette;
  store?: EngineStore;  // present if boot(...).engine_store was supplied
};

The store field is optional — boot() and the test harness only attach it when explicitly given an engine_store instance. Game code that wants persistence can pass one in or query for it:

sch.add("post", (w, ctx) => {
  if (!ctx.store) return;  // headless test mode
  // ...
});