Zeni
Flick. Hit one. Keep it. A coin-flicking game for the browser, based on the traditional Japanese game zeni hajiki (銭はじき, "coin flicking"). Play the computer, a friend or someone new, on your phone or computer. It installs like an app and works offline.
Play now: zeni.dammy.dev
How to play
Coins are scattered on a round table with an open edge. Tea cups sit in the way.
- On your turn, touch any free coin (one that isn't touching another), drag back and let go.
- Hit exactly one other coin and you keep it. Then shoot again with the same coin, from where it stopped.
- Hit none, or two or more, and your turn ends.
- Anything that falls off the table goes to your opponent, and your turn ends.
The game ends when one coin is left, no coin is free, or 40 shots have been taken. Most coins wins.
Features
- Play the computer at three levels (Beginner, Skilled, Master), offline.
- Online play: Quick Match against someone at your level, or a friend with a room code or link. Rated games, a global leaderboard and six tiers from Amateur to Legend.
- Challenges: challenge players you've met, and see who challenged you on the home screen.
- Daily puzzle: the same table for everyone each day. Keep as many coins as you can in three turns, then share your score.
- Best of 3, three tables (Easy with no cups, Medium with 4, Hard with 7) and places you unlock as you climb.
- A 3D table, characters with their own reactions, sounds and haptics.
- A short interactive tutorial.
- No email or password: you get a player code to sign in on another device.
How it's built
| Part | Built with |
|---|
| Game | TypeScript, three.js for the table, plain DOM and CSS for menus |
| Physics and rules | Deterministic simulation in shared/, run identically by the browser and the server |
| Server | Cloudflare Workers, with one Durable Object per game room, the Quick Match queue and the online count |
| App | Installable PWA with vite-plugin-pwa |
| Build and tests | Vite and Vitest |
The server plays every shot itself, so results can't be faked by a modified client.
client/ the game in the browser: screens, 3D table, input, sound
shared/ rules, physics, computer player, ratings, protocol
server/ Worker, Durable Objects (Room, Matchmaker, Presence), API
tools/ simulators, online test bots, asset generators
public/ icons, sounds, privacy page, headers
Run it locally
Needs Node 22 (see .nvmrc).
npm ci
npm run dev
Then open http://localhost:5173
Useful scripts
| Command | What it does |
|---|
npm test | Run the unit tests |
npm run typecheck | Check types for the client, server and tools |
npm run build | Typecheck and build for production |
npm run simulate | Play many computer-vs-computer games to check balance |
npm run play-online | End-to-end test of online play against a running dev server |
Credits
- Sound effects from Kenney (CC0): Impact Sounds, Casino Audio and RPG Audio.
- Based on zeni hajiki, a traditional Japanese children's game.
License
MIT. The Kenney sounds are CC0 and free to use without credit.
