Dots and Boxes

Controls

• Tap a faint line to draw it. With the keyboard, Tab to the board, move between lines with the arrow keys and press Enter or Space.
• Choose to play against the AI (beginner, standard or advanced), practise against it with undo, or pass one device between two players.
• Start an empty 3×3, 4×4 or 5×5 board, or one of twelve positions where every remaining move gives something away.

The rules

• Each turn draws exactly one unused line between two neighbouring dots.
• Every box the line completes goes to the player who drew it. If it completed at least one box, the same player moves again; otherwise the turn passes.
• One line can complete two boxes at once, for two points.
• The game ends when every line is drawn. More boxes wins; equal counts are a draw.

Scoring, saving and limits

Your score is your number of boxes. Games against the AI are recorded per level on this device as won, lost or drawn; practice and two-player games are not.

The game in progress, its full move history and your record are kept on this device; the board is rebuilt from the history when it loads. Download a backup to move it; Clear this game deletes only this game's data.

The beginner AI plays randomly; the standard AI takes free boxes and avoids handing over a third side; the advanced AI searches ahead with a fixed limit on positions examined and falls back to the standard rules when the limit is reached. No AI is claimed to be perfect.

Questions

Why did I get another turn?

You completed a box. Completing at least one box always gives the same player another move — that is what makes long chains of boxes so valuable.

Why are the twelve positions interesting?

Each is a position from a real sequence of legal moves at the point where every line left gives the opponent at least one box. Deciding which chain to give away is the heart of the game.

Can I play against someone online?

No — everything runs on this device. Two players can share one screen and take turns.