---
title: "One-shotting a Raccoon Heist Game with Codex + GPT-5.6 Sol Ultra: Results Beat Claude Fable 5"
source: "Simon Willison 博客（Atom）"
source_tier: "t2"
url: "https://simonwillison.net/2026/Aug/7/moonlight-mayhem/#atom-everything"
permalink: "https://feed.astralor.com/items/itm_18e9715f563cefab712bce59"
published: "2026-08-07T19:18:09.000Z"
score: 70
channel: "ai"
tags: ["Claude Fable 5","GPT-5.6 Sol Ultra","OpenAI Codex","Game Design","Generative AI","Coding Agents"]
---

# One-shotting a Raccoon Heist Game with Codex + GPT-5.6 Sol Ultra: Results Beat Claude Fable 5

## AI commentary

> This type of side-by-side test of different agents with the same prompt reveals more about real development experience than vendor demos. If you're choosing a coding agent or planning multi-agent workflows, this result is worth a close look; especially Sol's sub-agent mode in complex game generation, and the fact that it still missed a visual glitch during screenshot review — both are meaningful signals about capability boundaries.

## At a glance

Simon Willison ran the exact same prompt on Codex Desktop's GPT-5.6 Sol Ultra (with aggressive sub-agent use) to build a full game from a four-year-old GPT-3 concept. The result, Moonlight & Mayhem, puts you in control of raccoons in a museum, rescuing teammates and stacking up to steal the Golden Sardine — much closer to the original heist premise than Claude Fable 5's version. The initial output had a bug where each raccoon's eyeball was enlarged into a giant black sphere floating overhead, but a simple follow-up prompt fixed it. The entire process took 52 minutes, with Codex also generating textures and assets along the way.

## Key points

- Codex Desktop + GPT-5.6 Sol Ultra produced a noticeably better heist-themed game, Moonlight & Mayhem, from the identical prompt
- The gameplay evolved from 'collecting coins in a backyard' to 'rescuing crewmates and stacking up to steal the Golden Sardine', staying truer to the original Raccoon Heist concept
- The first pass had a visual bug where raccoon eyeballs became giant black spheres, which Codex failed to spot but the user fixed with two quick prompts
- Codex took 52 minutes to finish the project and generated textures and images along the way; the full transcript was published

## Full text

Moonlight & Mayhem (Raccoon Heist by Codex + GPT-5.6 Sol Ultra) On Wednesday I wrote about One-shotting a Raccoon Heist game using Claude Fable 5, where I had Claude Fable 5 build a full working game from a premise I generated with GPT-3 and DALL-E four years ago. I decided to pose the exact same 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 - GitHub repository here, including the textures and prompts it generated using gpt-image-2. Your browser does not support HTML5 video. 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. 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. I shared the full Codex transcript 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 cost estimate for that session if I had been paying full API prices as opposed to using my monthly Codex subscription: Tags: game-design, ai, openai, generative-ai, llms, coding-agents, codex, gpt

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