Simon Willison, who builds open source data tools such as Datasette and writes widely read notes on AI models, says October 2026 is an inflection point for vibe coding games. Vibe coding means describing what you want and accepting the result without reading the code. His claim is that Claude Opus 5.5 improved at the parts of game making that earlier models struggled with.

Fun was the missing piece

Willison lists where he sees progress: “Claude Opus 5.5 in particular exhibits meaningful improvements in several areas needed to build a compelling game,” including 3D modeling, music generation and game design.

Game design is the one he stresses. Models have long produced something that looks like a game. In his words, “The challenge has been getting to a game that’s actually fun to play.” He adds: “I didn’t think the models could do it. Then I tried telling Claude Opus 5.5 to ‘Make it a LOT more fun’… and it did.”

He says he built four games over the past few weeks that he enjoyed playing, without looking at the code. They are Tree Appreciator, a fantasy village adventure called Emberwick, a real-time strategy game called Battle Drones, and a pumpkin farming game. They run in the browser, and he reports that telling models to use three.js, a JavaScript library for 3D graphics, works well.

One person’s taste, on small games

The games are the evidence, and Willison is the only judge of whether they are fun. He reports that the pumpkin farmer took Opus 5.5 nearly two days and millions of tokens, and that Emberwick needed “quite a bit of additional playtesting and prompting,” mainly because of gameplay problems. He also says GPT-6 Astra “can absolutely build a game,” but that its sense of fun does not match Opus 5.5’s.

BuilderWithin’s read is that the transferable part is the prompt, not the games. “Make it a LOT more fun” is a vague instruction, and a loop of playing, reacting in plain language and asking again may serve a non-engineer better than a design spec written up front. Nothing here shows that loop works beyond one person’s taste.

The scope is also small. These are browser games made by one person, not shipped products with players, balance problems or live operations. A game someone enjoys for fifteen minutes is a different bar from one they return to.

Credit for AI-made work

Willison is direct about the ethics. One section is titled “Four times as insulting,” and he writes that he will not enter his vibe coded games in traditional game jams or competitions: “I don’t feel like I’ve earned that right.”

If you publish an AI-made game, say plainly which parts the model produced.

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