JGengine

This skyline is being generated in your tab by @jgengine/core

Make a game that with jgengine.

That sentence is the whole interface — a coding agent builds the rest on a pure-TypeScript SDK. Each pitch you see regrows the city below from one seed, live, using the same generators a shipped game runs.

Drive the generator yourselfSee every system live
seedneon-harbor-042

View source, honestly

That skyline is a function call.

The hero above isn't a render farm loop — it's the published npm package generating a city in your tab. Same code, same seed, same city in the editor, in a game, on a server. Everything on this site that moves is the engine moving.

what-you-just-watched.ts
import { generateCity } from "@jgengine/core/world/cityGenerator";
​
// The skyline on this page — streets, lots, loops — comes from this
// one call, running in your browser tab. No video, no mockup.
const city = generateCity(
  {
    seed: "neon-harbor-042", // the HUD shows the seed on screen now
    streets: { gridness: 0.88, boulevards: 0.32, winding: 0.12 },
    lots: { footprint: { w: 13, d: 11 }, setback: 3 },
  },
  230,
  230,
);
// → identical city on every machine: deterministic by contract.
PlaygroundDrive every dial yourself

The same generator with sliders: gridness, winding, boulevards, lots — regrown live in 3D on every drag, plus the exact RPC to bake your layout into a game.

CapabilitiesEvery system, running

Wind fields swaying grass, cables you can drag, terrain you can reshape — live specimens next to the few lines that import them.

GamesPlay what agents built

Whole games built on the SDK, playable right here — the proof that the one sentence works end to end.

How it works

From prompt to playable in three moves

01

Open any coding agent

Claude Code, Cursor, Codex, Copilot — whatever you already use. No special install for you.

02

Say the line

Make a game that … with jgengine. That is the whole interface. The agent uses the CLI and skills underneath.

03

Play the result

A complete, verified game on the SDK — not a demo slice — built from the same skills this site documents.

your agent — chat

you

The SDK

Eight packages, one-directional layering

core imports nothing. Every layer above it earns its dependencies. Your game imports what it needs and nothing more.

Render shell

React + three.js — the only package that renders

@jgengine/shell

R3F canvas, orbit + first-person camera, input, HUD mounting, GameUiPreview.

Your next game is one prompt away.

Paste this into your agent. That is how people build with JGengine outside the monorepo.

›Make a game that ... with jgengine
Star on GitHub