Dots and Boxes vs Computer

How to play Dots and Boxes

Dots and Boxes is the classic pencil-and-paper strategy game, first published in the 19th century by the French mathematician Édouard Lucas. Two players take turns drawing single lines on a grid of dots. Whenever a line closes the fourth side of a small square, the player who drew it claims that box — and immediately moves again. Simple as the rules are, the game hides surprising depth: whole matches are decided by who is forced to open the first chain of boxes. Play a friend on one screen, or challenge the computer at three difficulty levels on 4×4, 6×6 or 8×8 boards.

The goal

Own more boxes than your opponent when the board is full. Every completed box is tinted with its owner’s colour — Blue for player 1, Amber for player 2 — and counts as one point. Because our boards have an even number of boxes, a perfectly level score (and so a draw) is possible.

The board

The board is a square lattice of dots. The default 6×6 game means 36 boxes drawn on a 7×7 grid of dots, with 84 possible lines. Tap or click between two neighbouring dots to draw the line there — on a touch screen simply tap near the middle of the edge you want, and the closest free edge is chosen for you.

How a turn works

• On your turn you draw exactly one line — horizontal or vertical — between two adjacent dots. You may draw anywhere on the board; lines never need to connect to your earlier lines.
• If your line completes the fourth side of a 1×1 box, you claim that box: it is filled with your colour and scores one point. A single line can even complete two boxes at once, scoring both.
• Completing at least one box grants you another turn immediately. You keep moving for as long as every line you draw closes a box.
• Because of the extra-turn rule, boxes often fall in chains: capturing one box gives the next box its third side, letting you capture that one too, and so on down the corridor — a single turn can sweep many boxes.
• If your line completes nothing, your turn ends. Beware of “unsafe” lines that give any box its third side — you would be serving that box, and possibly a whole chain, to your opponent on a plate.

Winning (and drawing)

The game ends when every box is owned. Whoever owns more boxes wins — on the 6×6 board you need 19 of the 36. If both players own the same number (8, 18 or 32 each, depending on board size), the game is a draw. In the two-player game a banner announces the winner; against the computer a win earns ranking points.

Playing the computer (ranked)

In “Dots and Boxes vs Computer” you pick the board size, who moves first and one of three levels. Easy plays loosely and misses captures, so beginners can win. Normal grabs every box on offer and never gives away a box while a safe line exists. Expert adds real endgame technique: it counts chains, sacrifices the smallest one when forced to open, and uses the double-cross to keep control. The computer thinks entirely on your device and works offline. Beat it to earn ranking points — Easy +10, Normal +30, Expert +100 — and your best result appears on the leaderboard when you sign in.

Strategy: chains and the double-cross

• Count the safe moves. Early on, draw only lines that do not give any box a third side. When the safe lines run out, somebody must “open” a chain — the whole midgame is a fight over who runs out of safe moves first.
• See the board as chains. Boxes connected through shared missing walls form corridors; once one box of a corridor is opened, the entire corridor can be eaten in a single turn. Keep the chains you may have to give away short, and the chains you hope to receive long.
• When you must open a chain, open the shortest one. Giving away two boxes now to receive a five-box chain later is an excellent trade.
• Master the double-cross: when your opponent opens a chain, do NOT always eat it whole. Take all but the last two boxes, then close the far end with a line that offers both boxes back as a 2-box domino. Your opponent gains just two boxes — and is then forced to open the next chain for you. Repeated double-crosses let one player run the entire endgame.
• Watch the chain-count parity. All three of our boards use an odd dot grid (5×5, 7×7 or 9×9 dots), so as a rule of thumb the player who moves first wants an even number of long chains to form, while the second player fights for an odd number. Steering how many chains the board splits into — while safe moves still exist — is what expert play is really about.

Frequently asked questions