How to play
You probably played this one on the back of a school notebook. Here the grid is fixed at 6 × 6 dots, which gives 25 boxes and 60 possible lines. Red always opens the game.
On your turn you tap the gap between two neighboring dots, horizontally or vertically, and a line appears there. Most of the time that is the whole turn and play passes to the other side. The exception is the rule that drives everything: if your line is the fourth side of a box, that box is filled with your color and you draw again straight away. One line in the middle of the grid can finish two boxes at once, and a lucky run can keep you drawing for a long time.
Taking a box is never forced. If a box has three sides, you can ignore it and draw somewhere else, which sometimes turns out to be the clever move (more on that below).
When the last of the 25 boxes is filled, the side with more boxes wins. Because 25 is odd, a draw can’t happen.
Controls on the screen
- Opponent: choose Computer or Friend. Against the computer you play red and move first; with Friend, two people share the device and take turns on one grid.
- Difficulty: Easy, Medium or Hard, shown only when you play the computer.
- Hint marks a good line for whoever is to move.
- Undo takes back one line against a friend, or your line together with the computer’s reply.
- New game clears the grid.
The status line under the board keeps the running count as “Red · Blue”, and the most recent line is highlighted so you can see what your opponent just did. Your game is saved after every line, so you can close the page and come back.
Chains and the endgame
The opening of Dots and Boxes feels harmless: both players draw lines that don’t give anything away. Eventually every remaining line puts a third side on some box, and from then on the game is about chains, rows of boxes linked so that taking one opens the next.
Whoever has to move first into a long chain usually hands the whole thing over. That’s why the endgame is really a fight over who runs out of safe lines first. A loop (a chain that closes on itself) behaves the same way, except the person who takes it has to give back four boxes, not two, to keep control.
The key trick is the double-cross. When your opponent opens a chain of three or more boxes for you, take all of them except the last two, then draw the line that leaves those two as a pair for your opponent. They get two boxes, but then they have to open the next chain, and you collect it. Over two or three chains this usually wins by a wide margin.
Strategy
- Avoid the third side early. A box with three sides is a free gift. In the opening, prefer lines that leave every box at two sides or fewer.
- Count safe moves. In the middle game, try to see how many harmless lines are left. If the number is wrong for you, create or break a chain to change it.
- Short chains are cheap. Giving away a chain of one or two boxes costs little. Long chains are where games are decided, so sacrifice small ones to make your opponent open the big ones.
- Don’t grab automatically. Before closing the last boxes in a chain, ask whether the double-cross keeps control. Sometimes refusing two boxes earns you ten.
- Use Hint to learn. On a friendly game, compare your instinct with the suggested line and see where they differ.
About the computer
The computer searches a few moves ahead. It closes any box it can and avoids drawing a third side when it has a choice, and its scoring counts both the box difference and the boxes ready to be taken. It was not taught chain theory directly, so the double-cross is something it finds only when its search happens to reach far enough. That makes long-chain endgames the place where a human can outplay even the Hard level. In testing between levels, Hard beat Medium in all 8 games and Medium beat Easy in all 12.
If you like small, tactical grid games, try Ultimate Tic-Tac-Toe or the stone-placing duel Hex.
