const Position = list(
  quantized(-16, 16, { step: 0.01 }),
  3,
);

const Entity = object({
  id:       uint16(),
  position: Position,   // 6 bytes
  rotation: quat(),     // 7 bytes
});

const WorldSchema = object({
  frame:    uint32(),
  entities: list(Entity),
});

const { pack, unpack } = build(WorldSchema);

const bytes = pack(state);  // → Uint8Array
const back  = unpack(bytes); // → WorldState