Join two dots with a line. Draw the fourth side of a square and it's yours — and you go again. That's the whole rule set, and it hides a game about chains, sacrifices and counting that takes about ten minutes to start seeing and a long time to stop enjoying.
The goal
A grid of dots. On your turn you draw one line between two dots that are next to each other, horizontally or vertically. If that line completes the fourth side of a box, you claim the box — and you immediately go again. When every line is drawn, the player with more boxes wins.
The going-again rule is what makes this a game rather than a colouring exercise. One line can hand your opponent five boxes in a row, and the last of those five leaves them still on move, having to give you something back.
Controls
- Tap or clickThe gap between two dots. Anywhere near it will do — the board picks the nearest undrawn line to your finger.
- Press and slideThe line is previewed while you hold, and only committed when you let go. Land on the wrong one and you can slide to the right one before releasing.
- NStart a new game. R does the same.
- EnterOnce a game is over, play the next one. Space works too.
- EscOpen the settings sheet.
The tap target is a distance rather than a rectangle, which is why the board feels forgiving on a phone: nearly every pixel belongs to some line, and neighbouring lines never fight over the space near a dot.
Board sizes
Three, and they are genuinely different games rather than the same one scaled.
- 3 × 3 — nine boxes. Short, sharp, and small enough that the whole thing can be worked out in your head. The right size for learning what a chain is.
- 5 × 5 — twenty-five boxes. The default, and the size where chain play starts to decide games rather than decorate them.
- 7 × 7 — forty-nine boxes. A long game with a real middlegame, where you spend a while making safe moves and both players are quietly counting.
The two modes
Versus the computer
Pick a level and who opens — you, the computer, or random. When the computer takes a chain it draws the lines one at a time rather than all at once, so you can watch a five-box run happen instead of having the score jump and being left to work out what you gave away.
Pass and play
Two people, one device, taking turns on the same board. It keeps its own tally, separate from your record against the computer.
The three computer levels
Casual
Takes any box it's handed, and only about half the time bothers to check whether the line it's about to draw is a gift. It gives away chains for nothing. Beatable by anyone, on purpose, and the right setting while you're still working out which moves are safe.
Sharp
Takes every box on offer, never volunteers a third side while any safe line remains, and when it finally has to give something up, gives up the smallest thing on the board. What it does not do is chain play: it will happily eat a long chain and then hand you the rest of the game. That hole is exactly what a decent player learns to punish, and punishing it is the moment this game clicks.
Ruthless
Everything Sharp does, plus the two ideas that actually decide games at this size. It plays the all-but-two sacrifice — declining the last two boxes of a chain so that you are the one who has to open the next one — and once few enough lines are left it stops guessing and solves the rest of the game exactly, playing the endgame perfectly. Ruthless does not miscount.
Tips
Learn which lines are safe
A line is safe if it doesn't give a box away — that is, it doesn't leave any box with three sides drawn. Early on, nearly everything is safe and the moves barely matter. The game properly begins the moment the safe lines start running out.
Whoever runs out of safe moves first is usually the one who loses
Because that player has to open the first chain, and the rest of the board tends to fall the same way afterwards. So while there are still safe lines about, prefer the ones that leave the most safe lines behind. You aren't playing for boxes yet — you're playing to make the other person move first.
If you have to give something away, give away the least
When every remaining line opens something, don't just play anywhere. Look at what a greedy opponent would actually take from each option and pick the cheapest. A two-box gift now is very often better than a six-box chain later.
The double-cross is the whole endgame
When you're handed a chain, taking all of it feels like winning and usually loses. Take everything except the last two boxes, then play the line that leaves both of them free for a single move. Your opponent takes those two — and is then out of safe moves and must open the next chain for you. Two boxes bought back the entire rest of the board.
The exception matters: take the whole chain when it ends the game, or when there's still a safe line left on the board afterwards. If you'd be the one forced to open next, that's when you decline the last two.
Count the chains before you're forced to
By the middle of a 5 × 5 you can usually see how the rest of the board will break up: how many long chains are left, and who has to open the first one. That count is the game. Play the middle of the board with the end of it already worked out and you'll beat Sharp regularly and take games off Ruthless.
Start on 3 × 3
Nine boxes is small enough to see the whole thing at once, so the double-cross stops being a trick you were told about and becomes something you notice. Then move up.
Good to know
- Your tally is kept on your device, with a separate one for pass and play, and it remembers your best box count for each grid size — so 3 × 3, 5 × 5 and 7 × 7 each have their own record to beat.
- Your settings are remembered between visits and the game opens straight into the setup you last played. The sheet only opens by itself on your first visit.
- No account, and nothing is sent anywhere. Clearing your browser data clears the tally and your settings.
- A reset button in the settings sheet clears the record when you want a fresh one.