# Kiln

> An 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.

## Table of Contents


### Guide

- [Introduction](/guide/introduction.md): What Kiln is, what agent-first means, and how the pieces fit.
- [Getting started](/guide/getting-started.md): Create a game with kiln new, run it, read its schedule and run its test.
- [Project layout](/guide/project-layout.md): The files of a Kiln game, the entry module, and how names come from exports.
- [Working with agents](/guide/agents.md): The loop a coding agent follows, AGENTS.md and kiln docs, and llms.txt.
- [A complete feature](/guide/first-feature.md): Health, hazards and a health bar end to end: data, systems, schedule, test.

### Concepts

- [Entities and traits](/concepts/ecs.md): Entities, traits, relations, Transform, queries and commands.
- [Systems](/concepts/systems.md): The three system forms, the context, Mut() and checked access, order and run conditions.
- [The schedule](/concepts/schedule.md): Phases, what happens in one frame, when changes become visible, and startup validation.
- [Resources and events](/concepts/resources-events.md): Singletons with res.get/res.mut, and typed events with their lifetime rules.
- [Prefabs and plugins](/concepts/prefabs-plugins.md): Named spawn recipes, and plugins that bundle resources, events, systems and hooks.
- [States](/concepts/states.md): State machines for menus, pause and game over: inState, onEnter, onExit, despawnOnExit.
- [Determinism](/concepts/determinism.md): Seeded Rng, the simulation clock, kiln check, and where determinism ends.
- [Hot reload](/concepts/hot-reload.md): Systems swap in place; other changes rebuild or reload, per the hotReload setting.

### Plugins

- [Plugins](/plugins.md): What is in CorePlugins, the opt-in plugins, and how to configure them.
- [Rendering](/plugins/render.md): MeshRef, interpolation, teleports, hierarchy, instancing, the camera, 2D mode.
- [Input](/plugins/input.md): Actions and the Input resource, bindings, and scripted input for tests.
- [Assets](/plugins/assets.md): Loading glTF, textures and JSON by path without blocking, Model, and headless loads.
- [Timers and tweens](/plugins/timers-tweens.md): Timer, Lifetime, Delayed events and Tweens, all counted in fixed steps.
- [HUD and UI](/plugins/ui.md): The HUD as retained data: text, bars, buttons, UiClick, and testing it headless.
- [Camera](/plugins/camera.md): CameraPlugin: follow a target with smoothing, bounds, zoom and trauma shake.
- [Saving](/plugins/save.md): savePlugin: save slots, persisted settings, storage, and testing saves.
- [Animation](/plugins/animation.md): Sprite-sheet and skeletal animation with one graph model, animators and frame events.
- [Physics](/plugins/physics.md): Rapier rigid bodies and colliders synced to Transform, collisions, raycasts and ordering.
- [Debug panel](/plugins/debug.md): The Tweakpane inspector: stats, pause and step, system timings, entity and resource views.
- [Shaders (TSL)](/plugins/tsl.md): Writing custom materials in TSL for WebGPURenderer, verified on Three.js 0.186.1.
- [Community plugins](/plugins/community.md): Vendoring community plugins with kiln add, the available plugins, and writing one.

### Testing

- [Scenario tests](/testing/scenarios.md): Headless scenario tests: fresh app, exact steps, scripted input, assertions.
- [Recordings and replay](/testing/recordings.md): Record play sessions in the browser, replay them headless, and keep them as tests.
- [Snapshots](/testing/snapshots.md): The world as JSON: snapshot options, kiln run, diffs and restoring.

### Reference

- [CLI](/reference/cli.md): Every kiln command and option.
- [Configuration](/reference/config.md): Every kiln.config.ts field, overrides, and the Vite and Bun setup.
- [Errors](/reference/errors.md): KilnError, the common errors and their fixes, and every error code.
- [Kiln design](/design.md)
- [Kiln API](/api.md)