LAST CROWN
A free roguelite card game for phones: beat duelists on an island, take their cards and rebuild your 20-card deck.
Official site siam-works.com, verified Nov 3, 2026. The game itself, hosted on the developer's own site (siam-works.com); linked as PLAY from the SIAM WORKS home page and from the developer's Zenn article.
Where to play
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- Play free — official siteBrowserReleasedFree
Runs in a desktop or mobile browser. No download.
Browser (no download) · Mobile · Official link verified Nov 3, 2026.
About LAST CROWN
A free roguelite trading-card game that runs in a phone browser in portrait, with no install, account, ads or purchases. On an island tournament you pick your next opponent from the duelists on offer, win the duel, open a five-card pack and take one of the loser's three ace cards, then rebuild a deck of exactly 20 cards from what you found in that run. After four stages come the tournament's gatekeeper, its host and a true final boss; a run takes about 40 to 50 minutes. The rules are kept deliberately small: both sides have 20 HP, there are no traps and nothing happens on the opponent's turn. The official page lists 169 cards across ten themes, 38 duelists with story scenes, three endings and a collection of cards you carry home. It can be added to the home screen and played offline, in Japanese or English. The developer, SIAM WORKS, says Claude Code wrote all of the code from a design document in about 23 hours to the first public version, and that the developer wrote no code; the design document and the first 150 card designs were worked out with ChatGPT, and all the art was made with ChatGPT.
How it was built
VerifiedIn a making-of article on Zenn the developer says the game was made by “me and Claude Code” and that the developer wrote not a single line of code. The developer handed Claude Code (the desktop app, in plan mode) a folder with the design document, the first 150 card designs and hand-off instructions; Claude Code asked four questions, wrote a plan and then built the engine, the computer opponents, the screens, sound and story, with tests and balance simulations, about four and a half hours after the request for everything except the art. The developer says it took about 23 hours from the request to the first public version, and 14 more updates over the next three and a half days. Design-side work happened before that: the developer prepared the design document and card designs by bouncing ideas off ChatGPT, and made all the character art, backgrounds and card art with ChatGPT. The sound effects and music are synthesized in the browser with WebAudio, with no audio files.
Spec-first: the developer wrote a design package (design document, a card master in Excel and JSON, and instructions for Claude Code with fixed rules and priorities) before asking Claude Code to plan and finish the game. Claude Code chose a TypeScript, React and Vite web app installable as a PWA, built a card engine driven by data rather than per-card code, and checked rule changes with computer-versus-computer simulations; the developer played on a real phone and overruled the simulations when the feel was wrong, for example reverting starting HP from 30 to 20. Per the article: 86 commits, about 22,000 lines of TypeScript and 315 tests at version 0.8.5.
- Engine / framework
- None (TypeScript, React and Vite web app, per the developer)
- Languages
- TypeScript
- Team size
- 1 (solo)Developer ReportedZenn (サイアムワークス)
- Initial build time
- About 23 hours from handing over the design document to the public release (23.5 hours in the article's table)Developer ReportedZenn (サイアムワークス)
- Development time
- Not disclosed
- Development cost
- Not disclosed
- AI-written code
- ~100% of shipped codeDeveloper ReportedZenn (サイアムワークス)
“作ったのは、私とClaude Codeです。…コードは1行も書いていません。”Verification notes: Claude Code, the 23-hour first build, the roles of ChatGPT (design sparring and all the art) and the build figures come from the developer's Zenn article of 25 Sep 2026, which links the official game page. Game contents, pricing (free, no ads, no purchases), devices and languages from the official page on siam-works.com, whose structured data gives 21 Sep 2026 as the publication date (modified 5 Oct 2026). The article counted 161 cards at version 0.8.5; the official page now lists 169. Solo development: the article describes only the developer and Claude Code, and the site calls itself a web engineer's personal site; the developer's name is not given, so location is not recorded. The article does not say whether the Claude Code work used a particular model. No calls to AI services during play are mentioned.
Development history
Published on the developer's site as a free browser game (publication date in the official page's structured data), about 23 hours after the developer handed the design document to Claude Code.
The developer publishes a making-of on Zenn; by then 14 updates in three and a half days, including a story expansion and rebuilt computer opponents, had brought the game to version 0.8.5.
DeveloperZenn (サイアムワークス)
Game performance
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Browser (official site)
Free, with no ads and no purchases, per the official page.
No public metrics recorded for this listing.
Not publicly available: Concurrent players (site), Monthly revenue, Gross revenue.
Sales & revenue (all platforms)
Browser game — there are no downloads to count.
Reviews & rankings
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Sources
| Source | Type | Published | Accessed |
|---|---|---|---|
| 企画書1本を渡して23時間で公開。Claude Codeでローグライトカードゲームを作って分かった「AIが完成させやすいゲーム」の条件 Zenn (サイアムワークス) · Japanese | Devlog | Sep 25, 2026 | Nov 3, 2026 |
| LAST CROWN｜無料ブラウザゲーム・カードを奪って組み直すローグライトTCG SIAM WORKS · Japanese | Official site | Sep 21, 2026 | Nov 3, 2026 |
| サイアムワークス ｜ Webエンジニアの制作と実験の記録 SIAM WORKS · Japanese | Official site | Not confirmed | Nov 3, 2026 |
