A small top-down rally game with a diorama look, for the browser. It is a free, open-source, non-commercial demo, made in eleven vertical slices. It has five cars from four eras, six point-to-point stages, five times of day, rain and snow, and a short career against nine simulated rivals, who also race as ghosts.

An AI coding agent, Claude Code with Claude Opus 5.5, wrote almost all of this game. First it made a desktop version in Unreal Engine 5, in about four days. Then it ported that game to the web. One developer gave the ideas, made the decisions and played every build. The making-of tells how.

• Claude Code (Anthropic): the agent that wrote the code and ran every tool
• Unreal Engine 5 (Epic Games): the first, desktop version, in C++
• Blender: all the meshes, from Python scripts that run headless
• ElevenLabs: sound effects and music
• three.js, Rapier, Vite and TypeScript: the web version
• GitHub Pages: the published game
• The developer's workspace: Omarchy, Herdr for the agent panes, the claude-code-status status line and the savvy-progress agents panel. How the developer works with Claude tells more.

Play in the browser: https://jason-c-dev.github.io/backroad-rally/

The game opens on the title screen. Choose career, quick stage or time attack, then a car and a stage. In time attack you race the ghost of your best run. The menus work with the keyboard, the mouse or a gamepad.

A gamepad also works: the triggers, the left stick, L1 for the handbrake, Y to recover and Start to pause. The reference has all the keys and URL options.

Now in the game:

• Career: four seasons from the 1960s to the 1990s, four rallies of two stages each, against nine rivals. Points, standings, restarts, damage that stays between the stages of a rally, and new groups, cars and bonus liveries to unlock.
• Ghosts: race the ghost of your best run, with the time gap on the HUD, and the rival ghosts with their names and your live position.
• Menus: a title screen over a live diorama, a garage with the spec sheet of each car, a stage select with the time of day, the weather and your best time, pause, results and settings (assists, camera, every volume, graphics quality, frame-rate limit). Best times, ghosts and the career stay in your browser.
• Six stages: finland, japan, alps, wales, arizona and vermont, about 3 km each, with jumps, bridges, a ford, a canyon and crowds. Each runs forward or in reverse.
• Five cars: swift and pip (1960s, rear-wheel and front-wheel drive), lama (1970s, mid-engine), quint (1980s, four-wheel drive turbo) and kaze (1990s, four-wheel drive turbo).
• Five times of day: morning, afternoon, sunset, night and fog.
• Rain and snow: the grip, the handling, the look, the effects and the sound change with the weather. Snow has ice on the tarmac.
• Dust, skid marks, damage, a full HUD, engine sound, crowds and music.
• Runs on a laptop: auto quality picks the graphics tier behind the loading screen, so the picture does not change or stop when the stage starts. It holds 60 fps on an integrated GPU. Chrome (WebGPU or WebGL2) and Firefox (WebGL2) work.
• Fast updates: each data file has a content hash in its URL, so a reload after a new version gets the new files at once. Models are compressed, and the menus get the files for the next stage in the background.

The game is a port of a desktop game that an AI agent made in four days. A team of background agents did the work, and each agent had a written brief. 221 automatic handling checks compare each car with the original, and a robot driver times every stage.

Ten hard problems needed real fixes. In one, the physics engine could not tell which triangle a wheel was on. In another, nobody could hear the crowds.

Read the full story, with the token count and the cost: The making-of backroad rally.

You need Node 24 or later.

npm ci
npm run dev             # http://localhost:5173/
npm test                # unit tests
npm run test:handling   # headless handling tests
npm run build           # production build into dist/

The technical reference has the details: URL options, quality tiers, effects, damage, HUD, audio, tests, asset conversion and browser checks.

To continue the game with Claude Code, start it in the repo folder. CLAUDE.md tells it where to begin.

• Inspired by art of rally by Funselektor Labs. This project has no connection with its makers and received no sponsorship from them. I bought the game myself, and I am a huge fan of Funselektor's work. You can buy art of rally for PC and consoles from its website.
• art of rally was inspiration only. Nothing was taken from it: no files, code, assets, sounds or music, and no binaries were reverse-engineered. The goal was to test Claude Code in a full game pipeline, with a game in this style, without using anything from the original game. Every model, texture, sound, track and line of code here is new.
• Rendering: three.js (MIT).
• Physics: Rapier (Apache-2.0).
• Sound effects and music generated with ElevenLabs.
• Engine and UI sounds are synthesised by the project's own scripts.
• HUD font: Inter by The Inter Project Authors (SIL Open Font License 1.1, public/fonts/OFL.txt).
• Made with Claude Code.

The code is MIT licensed; see LICENSE. Third-party libraries and fonts keep their own licences.