The board · pass-and-play, or against the computer
Backgammon.
Nothing hidden.
Two players, one screen. The board is drawn by this page’s own hand — twenty-four points, the bar, the trays — and the rules are enforced rather than trusted: the dice say what may move, every legal landing lights up when a checker is tapped, and a move that breaks the rules simply cannot be made.
All of it, computed here: entering from the bar, hitting a blot, doubles playing four, both dice when both can be used and the higher when only one can, bearing off exact or overshot, gammons and backgammons, the doubling cube. Two people can pass one screen, or the computer can take Red and play the same enforced rules against you. No account, nothing fetched and nothing sent — the match lives in this browser and nowhere else.
24 points · 15 checkers a side · the doubling cube · matches to 1, 3, 5 or 7 · dice from the browser’s own crypto
The board
Tap a checker. See what the dice allow.
Roll, then tap one of your checkers — a dot marks every quiet landing, a red ring marks a blot that would be hit, and the tray lights when a man can bear off. One die at a time, undo freely; the turn only stands once it is confirmed. When the dice cannot be played at all, the board says so and the turn passes.
The table
no match yet
White races toward the lower right and bears off into the lower tray; Red toward the upper right and the upper tray. The rail numbers are White’s own 1–24; the record writes each side’s moves in its own numbering.
The match
To 1, 3, 5 or 7 points.
Pick the length, then play to it. A game scores the cube times one — twice for a gammon, three times for a backgammon — and the record below writes down every roll and every play as it happens. An unfinished match is remembered in this browser: walk away mid-game and the position is still on the table when you return.
Match & record
The computer takes Red — it rolls, plays and turns the cube on its own. Switch mid-match and it picks Red up from wherever the position stands.
Starting a new match abandons the one on the table.
#match=5 deep-links a length.
About
Pass and play, played properly.
The move generator is the whole point of this page. It enforces, in full: entry from the bar before anything else moves; no landing on a point held by two or more; hits sending a blot to the bar; doubles playing four moves; the duty to use both dice when any sequence can, and the higher die when only one can be played; bearing off only with all fifteen home, exactly or — overshooting — only from the rearmost point. A play the rules forbid is never offered, which is also why the quick bear-off is sometimes refused: if playing the other die first uses both, both it must be.
The Crawford rule is OFF — a plain choice, stated plainly: the cube is live in every game of a match, however the score stands. In a 1-point match the cube is dead and the button never appears. A declined double scores the cube as it stood; gammon and backgammon are read off the final position, not claimed. There is no resignation button — drop a double, or play the position out.
The computer, when you ask for it, takes Red and plays through the same move generator a hand does — it can only choose among the legal turns, never invent one. Its judgment is a plain positional heuristic — the pip count, blots and their exposure, points made, the bar — and its cube is a pip-count rule of thumb. It rolls the same honest dice you do, one visible move at a time. Honest company, not a champion.
The dice come from the browser’s own cryptographic generator,
rejection-sampled so all six faces are exactly level. The match is
saved under one localStorage key — backgammon.match
— in this browser and nowhere else; nothing is fetched,
nothing is sent, and this property has no upstream data at all. The
generator carries its own test battery: twenty scripted positions,
each commented with the expected count, runnable from the console
— because a rules page that is quietly wrong is worse than
none.