How to play
Players take turns drawing one horizontal or vertical line between two neighbouring dots. If your line completes the fourth side of a box, the box is yours, it fills with your colour, and you must draw another line. When every line has been drawn, the player with more boxes wins. Tap or click between two dots to draw a line — on a computer, the line lights up as you point at it. Undo takes back your last line, along with any computer moves after it.
Computer levels
Easy grabs boxes when it notices them and otherwise plays loosely. Normal never draws the third side of a box while a safe line is left, and when it has to give boxes away it gives as few as possible. Hard also counts the chains and loops in the endgame and uses the double-dealing trick: it hands you the last two boxes of a chain on purpose so that you have to open the next, longer one. Pick “2 players” to play a friend on the same device.
Strategy tips
Early on, avoid drawing the third side of any box — that just hands a box to your opponent. Eventually every line gives something away, and the board breaks into long chains of boxes. The player who gets to take the long chains usually wins, even after giving away a few boxes earlier. When you take a long chain, consider leaving its last two boxes with a single line across their far end: your opponent takes those two but then has to open the next chain for you.