Sperm Race
A joke browser game with four modes about sperm racing to the egg, from 120 obstacle stages to a 90-second survival arena; the developer, who had never coded, says Claude wrote it as one HTML file.
Official site johnisking.itch.io, verified Nov 3, 2026. The developer's own itch.io page, linked from the developer's devlog on tokensave.app and its copy on Qiita.
Where to play
Every platform this game is on. Links are checked against official sources; we never host or mirror games.
- Play free — itch.ioitch.ioReleasedFree
Plays in the browser on itch.io. No download.
Browser (no download) · Mobile · Official link verified Nov 3, 2026.
About Sperm Race
A free comedy game that plays in desktop and mobile browsers, built on one joke: the race every one of us once won. It has four modes. Adventure has 120 hand-built obstacle stages across 12 chapters. Racing gives you a steering wheel, gas and brake to beat four rival sperm over three laps. In Derby you back one runner and drop obstacles on the track (slow, stun, wall, boost) to help it win. Survival asks you to last 90 seconds while cancer cells chase you, on six maps. Controls are a one-finger drag, with the wheel in Racing. You can change how your sperm looks. The browser version on itch.io has no ads and every chapter is open from the start; a donation button is optional. An Android version with ads and a room-code mode for playing with friends is on Google Play. The developer says they had never written code and built the first version in three days by describing it to Claude (Sonnet) in Korean. Claude returned a single HTML file, and all graphics and sound effects are drawn and synthesised in code; the music is free Pixabay tracks.
How it was built
VerifiedIn the developer's devlog, the developer, who says they had never written code or heard of game engines, described the game to Claude (Sonnet) in Korean and got back a single HTML file that ran in the browser; it was later wrapped as an Android app unchanged. Each new mode came from a one-line request (a map, obstacles, a racing mode, a derby mode, a survival mode). The devlog says Sonnet drew every character, background, track and maze in code and synthesised the sound effects in code; the only audio files are free music tracks from Pixabay. The code was made on the Claude Pro plan ($20 for one month). The itch.io page's AI disclosure ticks AI Assisted, Code, Graphics and Text.
Prompting only, with no engine: the developer describes a change, Claude returns a new HTML file, and the developer plays it. Per the devlog, the first file arrived in the early hours of 19 Aug 2026 and was replaced 16 times by the next afternoon, growing from 47 KB to 149 KB; store screenshots were taken on 21 Aug. The game contains no image files: graphics are drawn in code and sound effects synthesised in code, with free Pixabay music. The developer says building took three days and fixing bugs took 14 more, and that in the end a person had to find the bugs and have the AI fix them. Multiplayer (up to 10 players in Derby, 4 in the other modes) was added in an update after release.
- Engine / framework
- None (a single HTML file)
- Languages
- HTML
- Team size
- 1 (solo)Developer Reporteditch.io
- Initial build time
- 3 daysDeveloper ReportedTokenSave (Jonhisking)
- Development time
- Not disclosed
- Development cost
- $45Developer ReportedTokenSave (Jonhisking)
- AI-written code
- ~100% of shipped codeDeveloper ReportedTokenSave (Jonhisking)
“Claude（Sonnet）に韓国語で「こんなゲームを作りたい」と伝えると、返ってきたのはブラウザですぐ動く HTML ファイル1つでした。”Verification notes: AI use, the three-day build, the $45 cost (Claude Pro $20 for one month plus the $25 Google Play registration) and the art and sound being made in code come from the developer's devlog on tokensave.app (5 Oct 2026, Japanese, byline Jonhisking), which is also posted on Qiita; it links both the itch.io page and the Google Play listing. The devlog says the developer now uses Claude Max 5× but made Sperm Race on the Pro plan alone. AI code share is recorded as 100% because the developer says the code was made without writing any by hand (コードを自分で書かず). The 14 days of bug fixing come from the devlog's preview of its next part, which was not checked. The tie between accounts: the itch.io account JohnisKing, the tokensave.app author Jonhisking, and the Google Play developer Johnisking, whose support address uses the Qiita account name yunany90. Location is from the Google Play developer address (South Korea); the devlog also says the developer prompted Claude in Korean. Google Play (not a platform we list) showed the Android version on 4 Nov 2026 as rated 3+, with ads, an ad-free purchase, 100+ downloads and 5.0 stars from 7 reviews (observed; not recorded as metrics). Neither itch.io nor Google Play shows a content warning, and the game is a comic premise with no explicit content in the store text, so no age gate is set. The music is free Pixabay audio; no third-party IP is involved. The game was not played, and no AI runs during play.
Development history
Claude returns the first HTML version of the game; 16 revised files follow by the next afternoon.
DeveloperTokenSave (Jonhisking)Published free on itch.io as a browser game, announced in the devlog post “Sperm Race is out”.
Latest update of the Android version on Google Play.
ObservedGoogle PlayThe developer publishes the first part of a devlog on how the game was made with Claude.
Game performance
Each figure measures something different — concurrent players, owners, downloads and sales are never interchangeable and are never added together. Labels show where each number comes from.
itch.io
Free in the browser (HTML5) with no ads and every chapter unlocked; an optional donation button. Desktop and mobile browsers.
No public metrics recorded for this listing.
Not publicly available: itch.io rating, Gross revenue.
Sales & revenue (all platforms)
Browser game — there are no downloads to count.
Reviews & rankings
Not yet reviewed by our editors.
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Not currently ranked.
No player reviews yet.
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Sources
| Source | Type | Published | Accessed |
|---|---|---|---|
| Sperm Race by JohnisKing itch.io | Store page | Sep 3, 2026 | Nov 3, 2026 |
| Sperm Race is out — four modes, 120 stages, free in your browser itch.io (JohnisKing) | Devlog | Sep 3, 2026 | Nov 3, 2026 |
| 初心者がバイブコーディングでゲームを作ってみた — コード経験ゼロ、3日、$45 TokenSave (Jonhisking) · Japanese | Devlog | Oct 5, 2026 | Nov 3, 2026 |
| 初心者がバイブコーディングでゲームを作ってみた Qiita (yunany90) · Japanese | Devlog | Oct 5, 2026 | Nov 3, 2026 |
| Sperm Race: 4 Crazy Games on Google Play Google Play | Store page | Not confirmed | Nov 3, 2026 |
| Official game page (language check) JohnisKing | Official site | Not confirmed | Nov 3, 2026 |
- Languages
- The itch.io page and the release post say the game is available in 12 languages; the developer's devlog and the Google Play listing say 13. Neither lists them. (itch.io, TokenSave (Jonhisking), Google Play)
- Multiplayer
- The devlog says multiplayer (Derby up to 10 players, other modes 4) was added after release, and Google Play describes playing with friends via a room code; the itch.io page tags the browser version Singleplayer and does not mention multiplayer. (TokenSave (Jonhisking), Google Play, itch.io)
