Big Free Casino Poker Room

How it's built

The hand engine is pure and synchronous. Its state is plain JSON, so a hand can be saved mid-way and resumed, and it has no DOM and no timers. A separate director module asks the engine whose turn it is, feeds in actions and animates the events that come back. The computer players are also a pure module, so the same code runs at the live table and in a self-play simulator. Before the flop they score their two cards and compare the score to thresholds set by position and style. After the flop they run Monte Carlo equity against weighted opponent ranges, using an allocation-free seven-card evaluator. The table is a three.js oval whose layout comes from pure functions, and hand history lives in IndexedDB. We built it in a separate git worktree on its own branch, then merged it into the casino.

Built with

• Vite
• three.js
• JavaScript
• Monte Carlo equity
• IndexedDB
• node:test
• Cloudflare Pages

The hard parts

1. Getting the corner rules right

   A short all-in must not reopen the betting for players who already acted. Heads-up, the button posts the small blind and acts first before the flop. A bet nobody calls goes back, every all-in level makes its own side pot, and odd chips go to the first winner left of the button. Because the engine is pure, each of these has a plain unit test.

2. Opponents that do not feel like robots

   Bots estimate their chances against the hands each opponent is likely to hold, and a player who raised before the flop is given a stronger range than one who called. Each style sets how loose, aggressive, sticky and bluff-prone a player is, and a skill level adds noise to their read of their own hand. The better styles also build reads on you.

3. Eight seats on a phone screen

   The felt is a stadium shape that stands on its end on an upright phone and lies wide everywhere else. Seat, bet, card and pot positions come from tested layout functions, checked at every table size, and cards are drawn larger than life so they read at a glance.

4. Analytics hits lost to a security header

   While launching the room we found that the site's content security policy was blocking Google Analytics' collect endpoint on www.google.com, so hits were being dropped across the whole casino. Allowing that one endpoint in the policy fixed it, and the fix went out with the Poker Room deploy.