Gameable Engine

Deal damage and heal ​

Goal ​

Press H to remove 25 health and J to heal 10, with a short invulnerability window.

Files you will edit ​

  • src/game.ts

Steps ​

  1. Use this isolated game definition in the template shell. The prefab gives the player the built-in Health component; all hits go through one part.

    ts
    import { createDamage, defineGame, Health, prefab, type GameContext } from 'gameable';

const Player = prefab({ health: 100 });
const model = { bars: { health: { value: 100, max: 100 } }, message: 'Alive' };
const hits = createDamage({
  capacity: 4096,
  invulnerableSeconds: 0.5,
  onDeath() {
    model.message = 'Dead';
  },
  onRevive() {
    model.message = 'Alive';
  },
});
function health(ctx: GameContext): void {
  hits.step(ctx);
  if (ctx.input.pressed('KeyH')) hits.damage(ctx, ctx.player, 25);
  if (ctx.input.pressed('KeyJ')) hits.heal(ctx, ctx.player, 10);
  if (ctx.input.pressed('KeyR')) hits.revive(ctx, ctx.player, 0.5);
  model.message = hits.isDead(ctx.player) ? 'Dead' : 'Alive';
  model.bars.health.value = Health.current[ctx.player];
  ctx.hud.set(model);
}
export default defineGame({
  player: { prefab: Player, spawn: [0, 0, 0] },
  init() {
    hits.reset();
    model.message = 'Alive';
  },
  systems: [{ run: health, on: 'authority' }],
  snapshot: () => hits.snapshot(),
  restore: (state) => {
    hits.restore(state);
    // Derived from restored Health on the next system call.
  },
});

  2. The message is derived from health/death state each step, so restoring a game also restores its display. In combat, pass the attacker's entity as damage's final argument. On despawn always call hits.forget(entity) before ctx.despawn(entity) to clear reused ids. The engine snapshots Health; this part snapshots flags and i-frames.

Verify ​

sh
npm run dev

H changes the meter from 100 to 75; J changes it to 85. A second H within 0.5 seconds removes nothing. Wait between hits until dead: J cannot revive, while R restores 50 health. Healing never exceeds 100.

See also ​