UmbraA deterministic game engine for AI agents

2D and 3D games in TypeScript. The same level, seed and inputs give the same run, tick for tick, in Node and in every browser, so every run is a replay an agent can save, share and check.

Get started

Play the examples

GitHub

Games as data and systems

Components with Zod schemas, resources, events, systems in phases and a seeded RNG. Levels, inputs and replays are validated JSON.

Proof every tick

A state hash after every tick, exact checkpoints, and replays that reproduce in Node and in Chrome, Firefox and Safari.

2D and 3D physics

Rapier plugins for both, with characters, sensors and ray casts, all hashed and checkpointed. glTF models become colliders headlessly.

Agents that play your game

Beam search from checkpoints, a playtester that finds crashes, nondeterminism and unreachable outcomes, and an MCP server for any game.

Draw it any way

Mesh, Sprite, Camera and Light components that are saved but never hashed, drawn by Three.js or Canvas 2D, with a fixed-tick browser loop and event sounds.

Replays you can watch

Studio re-runs any replay, checks its hash and scrubs through it tick by tick.

Five minutes

npm install umbra-engine

import { defineComponent, defineGame, runGame, z } from "umbra-engine";

const Counter = defineComponent("counter", z.number().int());

// Each tick's input is added to every counter; reaching 10 wins.
const adder = defineGame({
  name: "adder",
  input: z.number().int(),
  components: [Counter],
  setup: (world) => { world.spawn(Counter(0)); },
  systems: [function add(world, n) { for (const [e, v] of world.query(Counter)) world.set(e, Counter, v + n); }],
  outcome: (world) => (world.first(Counter)![1] >= 10 ? "win" : undefined),
});

const r = await runGame(adder, null, { seed: 0, inputs: [3, 3, 3, 3] });
console.log(r.outcome, r.ticks, r.finalStateHash); // "win" 4, and the same hash everywhere

Then read Getting started, or open the playground to play the 3D room, the 2D collect game and the 2D physics platformer in your browser.