KilnAn agent-first game runtime

A fixed-step loop, a Koota ECS and a Three.js render bridge, built so a coding agent can add a feature with a few exports and one scheduling line, then check it headlessly.

Get started

Why Kiln

API reference

Features are exports

A trait, a system and one line in src/main.ts. Kiln names everything after its export, so file layout never matters and errors name the thing you wrote.

Mistakes fail at startup

Two unordered systems writing the same trait, an .after() pointing at another phase, a write to a read-only trait. The schedule rejects them before the first frame, with the fix in the message.

Headless and deterministic

The same seed and input script give the same world. Scenario tests step exact frames under bun test, and kiln run prints the world as JSON.

Eyes when you need them

kiln shot renders one frame in headless Chromium. Play sessions record in the browser and replay frame for frame in a test.

Batteries included

Input, assets, timers, tweens, a HUD, states, a camera rig, save slots, sprite and skeletal animation, and Rapier physics.

Docs for agents

kiln docs writes an AGENTS.md from your code and its JSDoc. This site is also served as llms.txt and llms-full.txt.

// src/systems.ts
/** Integrates Velocity into Transform. */
export const Movement = system([Mut(Transform), Velocity], ([t, v], { time }) => {
  t.x += v.x * time.step
  t.z += v.z * time.step
})

// src/main.ts
export default () =>
  createApp(config)
    .use(CorePlugins)
    .add(Startup, SpawnLevel)
    .add(Fixed, chain(PlayerMove, Movement, CollectCoins))

bash

kiln describe     # the schedule: phases, systems, reads/writes/order
kiln test         # headless scenario tests (bun test)
kiln run --steps 600 --snapshot Transform    # the world as JSON after 10 simulated seconds
kiln shot out.png # one frame from headless Chromium
kiln docs         # AGENTS.md from the code and its JSDoc