Quarter Sun Cove
A cosy farming sim about growing a giant pumpkin for the October weigh-off.
Official site simonw.github.io, verified Nov 3, 2026. Linked as the latest version from the developer's own post on simonwillison.net.
Where to play
Every platform this game is on. Links are checked against official sources; we never host or mirror games.
- Play free — official siteBrowserReleasedFree
Runs in a desktop browser. No download.
Browser (no download) · Official link verified Nov 3, 2026.
About Quarter Sun Cove
A cosy farming simulator in the browser: you tend a giant pumpkin through the year for a weigh-off, and grow regular pumpkins to sell during pumpkin season. Every character is an animal, and the town mayor is a pelican. Simon Willison says he wrote a spec in a Claude Code brainstorming session, then had Opus 5.5 Ultracode build the game over nearly two days, without looking at the code. It is free to play on GitHub Pages; the developer says he is still iterating on it.
How it was built
VerifiedA brainstorming session in Claude Code produced a spec file (SPEC.md); the developer then had Opus 5.5 Ultracode build the game over nearly two days, using millions of tokens. He says he told Claude to "surprise and delight the user frequently".
Spec-driven: a Claude Code brainstorming session produced SPEC.md, and Opus 5.5 Ultracode then built the game over nearly two days. The developer says it was vibe coded with no looking at the code. The page is HTML and JavaScript and loads Three.js 0.170.0 from a CDN.
- Engine / framework
- Three.js
- Languages
- JavaScript
- Team size
- Not disclosed
- Initial build time
- Nearly two days of agent build timeDeveloper Reportedsimonwillison.net
- Development time
- Not disclosed
- Development cost
- Not disclosed
- AI-written code
- Not disclosed
“Then I had Opus 5.5 Ultracode burn millions of tokens and nearly two days building it.”Verification notes: The post names the model (Opus 5.5 Ultracode) but not the tool; Claude Code is inferred from the linked brainstorming session, which is a claude.ai/code session. Model, build process and play link checked in the developer's own post. The game page is titled "Quarter Sun Cove"; the URL slug is pumpkin-farmer. The post links SPEC.md in github.com/simonw/pumpkin-farmer, but the repository root returned 404 to an anonymous fetch, so it is not listed as open source. The post does not say who made the art.
Development history
First described publicly in a post on simonwillison.net, with a link to the latest playable version; the developer says he is still iterating on it.
Developersimonwillison.net
Game performance
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Browser (official site)
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Not publicly available: Concurrent players (site), Monthly revenue, Gross revenue.
Sales & revenue (all platforms)
Browser game — there are no downloads to count.
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Sources
| Source | Type | Published | Accessed |
|---|---|---|---|
| The October inflection point for vibe game development simonwillison.net | Devlog | Oct 28, 2026 | Nov 3, 2026 |
| Quarter Sun Cove (game page) simonw.github.io | Official site | Not confirmed | Nov 3, 2026 |
| Official game page (language check) Simon Willison | Official site | Not confirmed | Nov 3, 2026 |
