Dots and Boxes

🕹️ How to play

1. How to start a game of dots and boxes: The page opens straight into a game — no start button, no sign-up, no room code. A first visit gets the 3x3 learning grid against the rookie computer. Tap the gap between two neighbouring dots and the line appears as a dashed preview with Cancel and Confirm below it; the line is only drawn once you confirm. You can keep your finger down and slide between neighbouring lines, and lifting it never commits, so a mistap costs you nothing.
2. How scoring works and why you draw again: Every box has four sides. Draw the fourth side of a box and that box is yours: it takes your stamp, your score goes up by one, and you must draw another line straight away. Closing a box is a reward and an obligation at the same time — you cannot pass, and that extra line is often what hands the next batch of boxes to your opponent. That single rule is where every tactic in dots and boxes comes from, and it is the sentence pinned above the board.
3. How to read the safe-lines and longest-chain counters: The readout above the board always shows two numbers. Safe lines left is how many lines you can still draw without leaving a box with only one side open — draw one of those and your opponent cannot close anything next move. The number turns amber once it drops to three or fewer. Longest chain is the length of the longest run of boxes whose fate is already linked: whoever draws inside it first gives the whole run away. Select a line that would give boxes away and the dashed preview turns amber and says how many.
4. How two players share one phone: Switch the mode to 2 player, put the phone between you and take turns tapping. Dots and boxes is a perfect-information game — you both see exactly the same board — so there is no hand-off screen and nothing to hide. The score card of whoever is to move lights up in that player's stamp colour, readable from across the table, and every line your opponent drew on their last turn stays highlighted until you play, so nobody has to argue about what just happened. Two-player games use confirm-before-you-draw instead of take-backs.
5. How long a game takes and when to move up a board size: Roughly: the 3x3 grid has 9 boxes and takes one to two minutes; 5x5 has 25 boxes and runs four to six minutes; 7x7 has 49 boxes and runs eight to twelve. Start on 3x3 — a full round there teaches the draw-again rule end to end — then use the Switch to 5x5 button on the result card. On 7x7 the lines sit too close together for a thumb, so confirm-before-you-draw is forced on and its switch is greyed out.

📖 Rules & variants

Board and legal moves: the board is a square lattice of dots. The 3x3 learning grid has 4x4 dots, 24 drawable lines and 9 boxes; the 5x5 standard grid has 6x6 dots, 60 lines and 25 boxes; the 7x7 challenge grid has 8x8 dots, 112 lines and 49 boxes. You may only draw a horizontal or vertical line between two neighbouring dots — no diagonals, no skipping a dot, no redrawing a line. Tapping a line that already exists does nothing at all and does not cost you a move; a red flash would just become noise in a game where both players misfire a dozen times a round. Tapping the middle of a box, a dot itself, or outside the board cancels whatever preview is pending.

Turns and chains: players alternate, one line per turn, and passing is not allowed — while any line is still unpainted, the player to move has to draw one. Lines belong to nobody, which is why this page draws them in a neutral off-white; only boxes have an owner. If your line closes the fourth side of a box, that box is yours, your score goes up by one and you must draw again. The turn only passes when you draw a line that closes nothing. When a turn closes several boxes, this page reveals them one beat at a time instead of repainting half the grid in a single frame, so you can see where each point came from.

One line, two boxes: the lines in the middle of the board have a box on each side. If both of those boxes are down to that one last side, drawing it claims both at once and scores two points — but it still buys only ONE extra turn, not two. This is the edge case people most often remember wrongly, so it is stated in the rules, in the FAQ and on the turn bar. Lines along the rim only touch one box, so they can never close more than one.

Scoring, endgame and who goes first: each box is one point and ownership never changes once the stamp lands. The round ends when every line has been drawn, and whoever holds more boxes wins. This page only ships odd-numbered grids — 9, 25 and 49 boxes — so the two scores add up to an odd number and a two-player round cannot end level. Going first is a small advantage, handled by alternating it: seat one opens rounds 1, 3 and 5, seat two opens rounds 2, 4 and 6, and the opening banner says who it is. Running totals are split by mode and level and live in this browser only; they are recorded once, at the moment a round is decided, so reloading never double-counts.

What differs between the two modes: the 2 player mode has confirm-before-you-draw on by default and no take-backs — a take-back button that either player can press on a shared phone only starts arguments, so the safety net sits before the line instead of after it. The vs computer mode has both: confirmation is on by default on touch screens, plus three take-backs per round. One take-back unwinds your last line AND the computer's entire reply — every line it drew while chaining, including the final one that handed the turn back — and leaves it as your move again. Take-backs leave no mark, never touch your record and are never reported anywhere. On 7x7 confirmation is forced on and locked, because the hit strip for each line is only around twenty pixels there, below the safe size for a fingertip.

Three computer levels, graded by what they will and will not do rather than by search depth: rookie only takes a free box about half the time and otherwise plays a random safe line, and never sets up a double-cross — a good fit for someone who has just learned the rules. Steady always takes every box it can and always clears a chain to the end; it plays a safe line while one exists and opens the smallest region when none does, which feels like playing a person who knows the rules. Sharp solves the endgame exactly and plays the double-cross in the midgame: it will deliberately leave two boxes on the table so that you have to open the next long chain. All three run inside this browser tab — no network, no opening book — so reloading mid-round brings back the same reply.

Three tactics you can use immediately: first, prefer safe lines, meaning lines that leave no box with a single side open. The safe-lines counter tells you how many of those are left, and the moment it hits zero, whoever moves next is the one who gives something away. Second, never draw the third side of a box early — that is just putting the box on a plate. Third, whoever opens a long chain first loses ground, so from the midgame on, count the safe lines: if they run out on your turn, you are the one who has to open. Turning that around is a matter of parity — making sure your opponent runs out of safe lines before you do.

One concrete line of play, solved exactly on a 3x3 endgame: the player to move faces a four-box chain that is already open, with a five-box chain still untouched elsewhere. Take all four greedily and you then have to draw again, and the only thing left to open is that five-box chain — the opponent eats all five and the round finishes 4 to 5. Now take only the first two, then draw a line that closes nothing, leaving the last two boxes as a domino that one line can claim. The opponent takes those two, has to draw again, and can only open the five-box chain — so you eat all five and the round finishes 7 to 2. Same position, and the only difference is being willing to give up two boxes. That is the double-cross, and it is why the sharp computer sometimes walks past a box it could close.

❓ FAQ