Claude Fable 5 autonomously builds a browser-based 3D raccoon heist game from a 2022 prompt

Simon Willison used a 2022 GPT‑3 prompt and two DALL‑E images to test whether Claude Fable 5 could autonomously build a playable browser game. He provided the original materials and a concise prompt instructing Fable 5 to create a mobile‑friendly 3D browser game, generate textures via OpenAI’s image API, and commit changes frequently for preview.

Fable 5 chose Three.js, vendored the library, and wrote a Python script to generate seven ground/wall textures using OpenAI’s gpt‑image‑2. It then implemented the game loop, guard flashlights, a patrolling dog with scent tracking, and a procedural WebAudio soundtrack without any audio files. The agent also added mobile touch controls and automated testing via Playwright across desktop and phone viewports.

The session produced seven commits on a GitHub branch, each verified by automated Playwright playthroughs. Fable 5’s notes.md documents design decisions such as the dog’s 12‑unit detection radius and 17‑unit escape gap, plus fixes for rendering bugs discovered during testing.

Willison characterizes the result as an impressive technical achievement but a mediocre game: the mechanics are simple, the difficulty low, and the entertainment value limited. He emphasizes that while agents can rapidly assemble functional software, designing genuinely fun experiences remains a human skill.