The October inflection point for vibe game development

What it claims

Simon Willison argues that Claude Opus 5.5 can now design games that are fun, not just games that run. His evidence is that a generic prompt, "Make it a LOT more fun", turned a dull prototype into a good one. Battle Drones, a Command & Conquer-style RTS, is the case he says convinced him. Its first versions were built in July 2026 with Claude Fable 5 and produced "a workable 2D" game that "wasn't great to play." Opus 5.5 transformed it after two prompts: "Make it a LOT more fun", then "Port this game to three.js". None of the four games took more than four hours of his own work, though Claude Code ran for many more hours on its own. He says he never looked at the code.

How it works

Willison describes a workflow in three stages:

1. Start in plain chat (claude.ai or chatgpt.com) with "Build a mobile-friendly three.js game where...". Tree Appreciator came from a single shot with no follow-up prompting.
2. Escalate in rounds. Emberwick went from an engine demo, to terrain, basements and a troll cave, to "turn this into an actual game... a magic system, make it really good."
3. Move to Codex or Claude Code once the project passes the proof-of-concept stage. For Quarter Sun Cove, a brainstorming session produced a spec file. Opus 5.5 Ultracode then spent "millions of tokens and nearly two days" building from it.

Prompts that worked include "Think hard about how to make sure it is both fun and beautiful", "a plot that isn't too cliche" and "surprise and delight the user frequently". The last one produced many small easter eggs. Telling the model to use three.js lets Claude build full-color 3D models, since it has no image generation model of its own.

Evidence

The evidence is the author's own play experience, with transcripts and playable builds linked. There is no benchmark. Willison ran the same Emberwick prompt sequence through GPT-6 Pro and judged the result to look great but play worse. He says GPT-6 Astra "isn't quite there yet" on fun and expects OpenAI to catch up by the end of 2026. He calls this an impression, not an exhaustive study.

How to use it

Battle Drones was released under the Apache 2.0 License in October 2026. It has 2 to 4 player multiplayer through a vibe coded WebSockets relay server, seven maps, a random map generator, replays, medals and rule "mutators". It also has an LLM-vs-LLM mode: the game advances five seconds, then pauses so each model can read the state and issue commands. A page lets users browse its 3D models. Gabriel Turpin forked it within a day as Panache, a steampunk Belle Époque version. Emberwick ships with an experimental level editor.

All four games are static HTML and JavaScript, hosted on GitHub Pages or Cloudflare Pages. Willison names three.js and Phaser as libraries the frontier models already know.

Limits

Emberwick needed substantial playtesting because of state bugs: a character could be in the wrong place to finish a quest after another story event moved them. Willison is not yet convinced by Quarter Sun Cove's mechanics. Players must time plantings so pumpkins ripen on the busiest October weekends, and he calls it less fun than Battle Drones. His audio-based multiplayer experiment gave a player a headache. He notes that many players reject AI-generated assets, citing complaints about slop at Valve's Steam Next Fest. He says he will not enter these games in traditional game jams.