peer2peergames

Dots and Boxes

The pencil and paper game, on a six by six grid of dots. Join dots with lines, close boxes, and keep the turn every time you do. It looks like a game for children and it is not: the whole of it is decided in the last dozen lines.

Play Dots and Boxes Leaderboard

The rules

  1. The board is a six by six grid of dots, which makes sixty lines to draw and twenty-five boxes to claim.
  2. On your turn, draw one line between two dots that are next to each other, across or down. A line that is already drawn cannot be drawn again.
  3. If your line is the fourth side of a box, the box is yours: it fills with your colour and your number. You then move again, and keep moving for as long as you keep closing boxes.
  4. One line can close two boxes at once, one on each side of it. Both are yours, and you still move again just once.
  5. A line that closes nothing passes the turn. There is no passing otherwise: while there is a line to draw, you draw one.

How a game ends

  1. When the sixtieth line is drawn, the game is over, and the last line always closes a box.
  2. The player with more boxes wins. Twenty-five is odd, so the game cannot end in a draw.
  3. A resignation or a missed deadline ends the game against that player: the deadline is set when the game is made, and running out of time loses it.

Worth knowing before you start

  1. The third side of a box is a gift. Whoever draws it hands the box to the other player, so the opening is spent drawing lines that give no box a third side.
  2. Those lines run out. Then every remaining line opens a chain of boxes for the other player, and the game becomes a question of who is forced to open which chain.
  3. The player who has to open the first long chain usually loses. The way out is the double-cross: when you are handed a chain, take all but the last two boxes and give those two away with a single line, so that your opponent, after taking them, has to open the next chain for you.
  4. Which is why counting the chains matters more than counting the boxes until the very end.

The seed decides who goes first and is published when the game ends, so the choice can be checked afterwards. Nothing else in this game is decided by chance.

Dots and Boxes terms

A chain
A run of boxes each with two sides still to draw, joined through the sides they share. Draw a third side on any of them and the other player can take the whole run.
A loop
A chain that joins back on itself. Opening one costs four boxes to keep control of, not two.
The double-cross
Taking all but two boxes of a chain and giving those two away together, so the other player has to open the next chain.

Playing it here

  • Against a person or the bot. The bot needs no account and starts at once. To play a person, be rated and keep your games, you need an account: an email address and a password.
  • At your own pace. Every move has a deadline you both see, from one minute to a week. A game can take an evening or it can take a fortnight.
  • Nothing to buy and nothing to win. No stakes, no prizes, no boosts, no undo. The only thing on offer is a place on a leaderboard, and only if you want one.
  • Every game can be checked. Anything decided by chance comes from the game's seed, and the seed is published the moment the game ends, so any finished game can be replayed and verified by anyone. See fair play.