Moonlight & Mayhem (Raccoon Heist by Codex + GPT-5.6 Sol Ultra)

Simon Willison used OpenAI's Codex Desktop running GPT-5.6 Sol Ultra to generate a raccoon-themed heist game called Moonlight & Mayhem, which he published on GitHub. The AI-produced game improved on an earlier GPT-3 version by featuring a museum heist where the player rescues raccoon crewmates, but it initially included a bug with oversized eyeballs that Willison fixed via prompts. Codex spent 52 minutes on the project, and the session's cost was estimated at full API prices via AgentsView.

Moonlight & Mayhem Raccoon Heist by Codex + GPT-5.6 Sol Ultra https://simonw.github.io/raccoon-heist-codex/ I decided to pose the exact same prompt https://simonwillison.net/2026/Aug/5/raccoon-heist/ the-fable-5-prompt to Codex Desktop running GPT-5.6 Sol Ultra - the mode where Sol makes aggressive use of sub-agents - to see how it would do. It produced a much better game Here's Moonlight & Mayhem https://simonw.github.io/raccoon-heist-codex/ - GitHub repository here https://github.com/simonw/raccoon-heist-codex/ , including the textures and prompts https://github.com/simonw/raccoon-heist-codex/tree/main/output/imagegen it generated using gpt-image-2 . The original GPT-3 generated game description included: In “Raccoon Heist”, you and your team of thieving raccoons are tasked with pulling off a series of daring heists. From robbing banks to stealing priceless art, no job is too big or too small for your furry crew. Fable's version had you as a single raccoon running around a back yard collecting coins and fish. GPT-5.6 Sol has you in a museum, rescuing your two other raccoon crewmates in order to stack on top of each other and bust the golden sardine out of its case. Much more heisty There was one catch though: the version produced from the one-shot prompt had a bug where each raccoon had an eyeball that was enlarged to the size of a giant sphere floating over their head You can play that version here https://static.simonwillison.net/static/2026/raccoon-heist-eyeball-edition/ . Despite reviewing screenshots during development Codex failed to spot and correct this bug. I fixed it by prompting: Why do the raccoons have huge black spheres on them? And then: Fix it Which resulted in this fix https://github.com/simonw/raccoon-heist-codex/commit/4e9a390dfbe80533324ee61a37aa661813c08446 . I shared the full Codex transcript https://github.com/simonw/raccoon-heist-codex/blob/main/transcript.md in the repository - I wish Claude Code had the same "copy as Markdown" feature. Codex spent 52 minutes on the project. Here's the AgentsView https://www.agentsview.io cost estimate for that session if I had been paying full API prices as opposed to using my monthly Codex subscription: Tags: game-design https://simonwillison.net/tags/game-design , ai https://simonwillison.net/tags/ai , openai https://simonwillison.net/tags/openai , generative-ai https://simonwillison.net/tags/generative-ai , llms https://simonwillison.net/tags/llms , coding-agents https://simonwillison.net/tags/coding-agents , codex https://simonwillison.net/tags/codex , gpt https://simonwillison.net/tags/gpt