Domino — Partner Dominoes

Double-six partner dominoes (4 players, 2 teams). You + an AI partner vs two AI opponents. Everyone draws 7 — the full 28-tile set, no boneyard. First team to 100 points wins.

Rules implemented

• Round 1 opens with the double-six (whoever holds it). Later rounds: the previous round's winner opens with any tile.
• Play counter-clockwise; match a tile to either open end; pass if you can't play.
• Round ends by domino (someone plays their last tile) or blocked (all four pass).
• Domino: the winning team scores the pips left in the opponents' hands. Blocked: the team with fewer combined pips wins the opponents' total; a dead tie scores nothing.

Table layout

The table is square (1:1). Tiles are drawn at a fixed size and never shrink — the chain starts in the middle and, when an arm reaches the edge, it turns the corner and runs along the border, coiling inward if it goes all the way around.

• The opening tile is the spinner. It lies flat toward whoever opened, so you can see who went out, and both arms leave it crosswise — one from each half, running in opposite directions. So if East opens 1|6, the answer to the 6 goes out one side and the answer to the 1 goes out the other.
• After that, doubles sit crosswise to the chain and everything else runs along it.
• Corners: a normal tile tucks into the corner square making an L; a crosswise double sits squarely beyond the end. Tiles always meet face to face.
• Pips are painted on the tile face, so they rotate with the tile.

A full 28-tile chain is 1372px of dominoes and needs a 580px square to coil cleanly. Smaller screens lay it out at that size and scale the whole table down, so tile size is still fixed for the entire round.

The opponents

Three difficulty levels, selectable during play.

• Easy — plays for weight only, ignores the table.
• Medium — tracks suits and passes, plays sensible dominoes.
• Hard — reads the table properly: who is void in what (from passes), which tiles are still unseen, which doubles are outstanding. It evaluates the position each move creates — how mobile it leaves each seat — and squeezes the player who moves next while keeping its partner alive.

The AI opens using the classic Venezuelan school — the regla de oro of El Tigre de Carayaca (Héctor Simosa Alarcón): lead the highest double that has company, fall back to the highest bare double, and with no doubles lead a heavy tile from your longest suit.

Measured over 600 mirrored matches (sides swapped so seat order cannot skew it):

Matchup	Win rate
hard vs medium	65.8%
hard vs easy	81.3%
medium vs easy	80.7%
hard vs hard	50.7% (sanity check)

Round review

After every round you can open a review of your own play. This is a team game, so the review is built on the partner doctrine of Héctor Simosa Alarcón, "El Tigre de Carayaca" (Ciencia y Arte en el Dominó). Two independent lenses:

Principles. Judged against the classic partner ideas, with a separate team-play score for how often your choices helped your side:

• Your role this round (el papel de los jugadores) — every seat is named relative to the opener and told what it is for. The mano plays for their own hand; the segunda blocks them; the tercera exists to keep their partner from passing; the pie tries to make the opener pass.
• Protecting your partner — never open a suit they have passed on, repeat their suit when you can, and as the tercera, follow the suit they opened.
• Punishing the opponents — leave suits they have failed on, and don't feed the suit the player on your right is developing.
• The opening — the regla de oro: the highest double with company; a bare double (en pelo) names your suit but leaves you void; with no doubles, a mixed lead tells your partner so (salida mata-doble).
• The close (la tranca) — scored by El Tigre's own arithmetic rather than hindsight. The cifra-base is 168 less the pips already on the table; halve it, and weigh it against your own points plus the heaviest tiles your partner could still hold (never counting suits they have passed on). Close only at or under that half. Closing and losing is called out directly: "la tranca es una jugada que no se debe hacer para perderla." A close you skipped that the count did not support is explicitly not treated as a mistake.
• Doubles — play them at the first chance, and only wage war on one when you know where it is and can truly hang it.
• Your own hand — don't throw la minga (your only tile of two suits) early, don't open a fresh suit you can't answer, and keep control of the ends.

Engine analysis. Separately, where your move ranked in the engine's own search, what it would have played instead, and why.

Forced moves are never counted against you.

Sources

• Héctor Simosa Alarcón ("El Tigre de Carayaca"), Ciencia y Arte en el Dominó — in particular the chapters on la tranca, cuadros, and hanging doubles.
• El papel de los jugadores
• 28 consejos para jugar al dominó por parejas
• La salida en profundidad

Run locally

npm install
npm run dev      # http://localhost:3000
npm test         # engine unit tests

Deploy to Vercel

npm i -g vercel
vercel           # log in with your account, accept defaults

Or push the repo to GitHub and import it at vercel.com/new.

Project structure

• src/engine/ — pure game logic (tiles, rules, scoring) + AI. No UI dependencies, so it can run server-side for online multiplayer in phase 2.
• src/components/ — the game table UI.
• src/app/ — Next.js app shell.

Online play

Private tables with a shareable six-character code. Create one, send the code to three friends, and empty seats can be filled by the computer (host's choice, with a skill setting).

Turn on the backend by following SUPABASE.md — one free project and three environment variables.

How it is kept honest. The browser never runs the rules and never holds the deck. It sends intentions ("play this tile on that end") to the server, which owns the authoritative game state, validates against the same engine the solo game uses, and replies with a view containing only that player's own tiles. Everyone else's hand is reduced to a count. Row level security denies browsers all direct database access, so hidden information stays hidden even if someone goes looking with the developer tools.

Other details:

• Identity without logins. A per-room token in localStorage is your seat. The schema already carries a user_id column, so real accounts and ratings can be added later without a rewrite.
• Disconnections. Your seat is held, and the computer covers for you so the table doesn't stall. Come back in the same browser and you get the seat back. With computer cover switched off, the game waits for you instead.
• Staying in sync. Clients poll their own view and reconcile by version number, so a slow reply can never overwrite newer state.

Roadmap

• Phase 1 (done): play vs computer.
• Phase 2 (done): private online tables with invite codes.
• Phase 3: public quick-play matchmaking, then accounts, ratings and match history — plus other game modes.