Matt Shumer's Claude of Duty puts you in a sunlit market street, rifle in hand. In the demo, the player moves past shop awnings, stalls and sandbags, then raises a scope to take a shot. You're watching a playable game running in a browser, with a world to explore and enemies to fight.
And it all began with one prompt.
One prompt, many rounds
Shumer used Claude Code with Claude Opus 5. His instructions asked separate AI agents to build different parts of the game and others to judge their work. The critics had to compare the results with real Call of Duty screenshots and send weak parts back for improvement.
He calls this a Gauntlet Loop: build, check, improve, repeat. Shumer says it continued for many hours without him stepping in to steer it. One prompt started the process; repeated work produced the game.
Every detail built in code
The project grew to roughly 55,000 lines of code. Its buildings, weapons, textures, animations and sounds were generated in code, without imported art or audio files. That includes the street you're moving through, the rifle you're aiming and the sound of each shot.
Call of Duty was the target, and Shumer's own notes acknowledge that the game hasn't reached that level. But getting this much into a working browser game is an achievement worth stopping for. He has published both the original prompt and the project code, so you can explore what was built.