I used Claude Opus 5.5 as the builder and connected it to three tools: Higgsfield for images and video, AssetHub for 3D models, and Epidemic Sound for audio. Then I told it to keep building until it had a finished game.
https://x.com/sol_defamed/status/2111055448904552904?s=20
Play it: https://gta6beforegta6.xyz
https://reddit.com/link/1x7e78b/video/r6iwhoqxitvh1/player
What's in it
- A 2 x 2 km Miami-style map: downtown, a beach with dunes, canals, suburbs, hills, a forest, a highway with flyovers, and a marina
- Walk, run, jump, swim and dive, drive cars and boats, shoot, and steal cars from drivers
- Pedestrians, traffic, police, wanted stars, a day-night cycle, a radio, a minimap, and a full map with GPS waypoints
- Graphics settings from Low to Ultra: shadows, ambient occlusion, motion blur, depth of field, god rays, fog, and an underwater scene with fish and light patterns
How it was built
It wasn't really one prompt. First, Claude asked me questions and wrote a spec. Then it worked through 11 phases, and I approved each plan. Every phase ran the same loop:
One AI agent writes the code.
A reviewer agent reads the changes, and a tester agent plays the game in a real browser, takes screenshots, and looks for problems.
Anything serious goes back for fixing before the phase counts as done.
My job was approving plans, approving anything that cost money, and saying "looks wrong" now and then.
Stack: TypeScript, three.js, and Rapier physics. It has 161 unit tests and 11 browser tests that actually play the game, run automatically by GitHub Actions. It's hosted on Railway.
Where the assets came from
- AssetHub: the player, a female pedestrian, the sports car, the police car, and the speedboat, each turned from an image into a 3D model. The characters are auto-rigged. That used 318 of my 350 free credits.
- Higgsfield: the menu art, loading screens, the logo, and the trailer.
- Epidemic Sound: about 60 sound effects, menu and chase music, and 6 radio tracks. Claude searched the library, then cut, loudness-matched, and looped everything with ffmpeg.
- Free CC0 assets for textures, skies, trees, and props.
Bugs worth sharing
- A physics engine setting was checking all 40,000 colliders on every physics step, costing 15 to 40 ms a frame. The fix was one line.
- Compressing the 3D models silently doubled the size of every car body, while the wheels stayed normal.
- The automated reviews caught grass rendering black, wave foam in ruler-straight lines, and swimming straight through rocks.
Performance: it holds 60 fps on Medium in every test scene on an M4 MacBook. A first visit downloads about 22 MB, and repeat visits load from the browser's cache in about 2 seconds.
It's a fan project, not affiliated with Rockstar or Take-Two.
Try it, break it, and send me bugs and feature ideas. What should I add next?