Dots and Boxes
Draw a line, complete a box, go again. The game is decided by who is forced to open the last chain, not by who grabs boxes early.
Taking every box you can is how you lose
The number of boxes is fixed before anyone moves, so the game is not really about collecting them — it is about who is forced to open the last chain. Once the board has been carved into chains, every chain you open is a gift, and the player who runs out of safe moves first hands over the endgame. That is why a beginner who greedily takes every available box usually loses to someone who declines them.
The technique that follows is the double-cross: when handed a chain of three or more, take all but the last two boxes and then deliberately give those two back. You lose two boxes and keep control, which means your opponent has to open the next chain instead of you. Strong play is about the parity of the number of long chains, decided long before any of them are opened.
How to use
- Click between two dots to draw a line.
- Complete the fourth side of a box to claim it and move again.
- Late in the game, taking every box you can is usually a mistake.
- Whoever is forced to open the last long chain generally loses.
Frequently asked questions
How do you play dots and boxes?
Players take turns drawing a single line between two adjacent dots. Whoever draws the fourth side of a box claims it and immediately draws again. When every line has been drawn the player with the most boxes wins. The rules take a sentence; the strategy does not.
Why is taking every box a mistake?
Because the total number of boxes is fixed before anyone moves, so the game is really about who is forced to open the last chain. Greedily taking boxes usually means finishing a chain and then having no safe move left, which hands the next and larger chain to your opponent.
What is a chain?
A run of boxes joined so that opening any one of them lets your opponent take the whole run in a single turn, because each completion grants another move. Once a board is carved into chains, the game becomes a question of who runs out of safe moves first and has to open one.
What is the double-cross?
The key technique. When handed a chain of three or more boxes, take all but the last two and then deliberately give those two back by drawing the line that leaves them joined. You lose two boxes but keep control, so your opponent has to open the next chain instead of you.
What is the chain rule?
A guideline about parity: try to make the number of long chains odd if you moved first, and even if you moved second. Since the player who opens each chain hands it over, the count of chains determines who is forced to open the last and largest one, and that is usually the game.
Should I ever refuse a free box?
Frequently, near the end. Taking a box is only free if it does not force you to open something bigger afterwards, and the double-cross exists precisely because declining two boxes to keep the initiative is often worth far more than the two boxes are.
Does going first matter?
It affects which parity you want, rather than giving a clean advantage. On boards where the natural chain count favours the second player, moving first is a handicap — which is why serious players think about parity from the very first move rather than only in the endgame.
How does board size change the game?
Larger boards give more room for long chains and make the parity battle more important, while very small boards are often decided by simple counting. A three by three is nearly tactical; a six by six is a genuine strategic game where the opening moves matter for reasons that only show up much later.
Is the game solved?
For small boards, yes — several sizes have been analysed exhaustively. For larger ones it is computationally hard, and the general problem of playing perfectly is difficult enough that competitive play still rewards understanding chains and parity rather than calculation.
How strong is the computer opponent?
It takes free boxes when they exist and otherwise avoids handing you one, which is enough to punish greedy play without being unbeatable. It does not reason about chain parity, so a player who understands the double-cross can beat it reliably — which is rather the point of the game.
Where did the game come from?
It was described by the French mathematician Édouard Lucas in 1889 under the name la pipopipette, which makes it considerably older than most paper-and-pencil games people assume it sits alongside. Elwyn Berlekamp later wrote a whole book on its mathematics.
Does the game save my progress?
No. Everything runs in your browser, nothing is stored or uploaded, and closing the tab loses the current board.
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