Yatzy in the browser. Add a few players in the lobby, then take turns at the same screen: roll up to three times, hold the dice you like, and pick a category on the score sheet. When everyone has filled all 15 categories you get a leaderboard.

I built it for the Distribueret Programmering course on the Datamatiker programme at Erhvervsakademi Aarhus. The game state lives on the server, Pug renders the pages, and the browser talks to a small JSON API for rolling, holding and scoring.

Scandinavian Yatzy, not American Yahtzee:

• Upper section 1s to 6s, with a 50 point bonus once it reaches 63
• One pair, two pairs (must be two different pairs), three and four of a kind
• Full house is three of a kind plus a pair of a different value, scored as the sum of the dice
• Small straight is exactly 1-5 (15 points), large straight is exactly 2-6 (20 points)
• Chance is the sum of the dice, Yatzy is 50

You have to roll at least once before you can score or hold dice.

Needs Node 22 or newer.

npm install
npm start

Then open http://localhost:8080. PORT and SESSION_SECRET can be set as environment variables. The secret falls back to a dev value, so set a real one if you put this anywhere public.

Each browser session gets its own game, kept in memory, so restarting the server clears all games.

npm test          # node:test
npm run coverage  # same, with a coverage report

• test/yahtzeeBrain.test.js covers every scoring category plus edge cases (four of a kind isn't two pairs, Yatzy isn't a full house, unrolled dice score 0)
• test/player.test.js covers the upper section bonus and that a category can only be used once
• test/routes.test.js uses supertest against the Express app: separate games per session, input validation on every route, the three-roll limit, holding dice, and a full two-player game through to the leaderboard

CI runs the tests on Node 22 and 24.

app.js              Express routes and the per-session game store
backend/            GameState, Player, Dice and YahtzeeBrain (scoring)
views/              Pug templates for lobby, game and end screen
assets/             Client JS, CSS and dice images
test/               node:test suites

MIT