About Flow

Pairs of coloured dots are scattered across a grid. Drag from one dot to its partner to join them with a line. Lines may not cross, and every cell on the board has to be used — joining the pairs is the easy half; filling the board while you do it is the puzzle. Every dot also carries a letter, so the board can be read without telling colours apart.

Drawing works the way a finger expects. A line runs cell by cell as you drag; run it back over itself and it shortens to where you are; touch a line anywhere and you carry on from that point; run into another colour's line and that line is cut short where you crossed it. Every board is made from its own answer — a single path through every cell, cut into pieces whose ends become the dots — so there is always a way to fill it, and any other way that fills it wins as well.

The daily challenge is a seven-by-seven board with seven pairs, the same for everyone, ranked on strokes and then time. A stroke is a run of drawing one colour, so a perfect board is one stroke per colour: every line drawn once and never touched again. Free play has five-by-five and nine-by-nine boards too.

Tips to win

• Start with the pairs on the edges: a line along the edge has only one side to worry about
• A pair of dots close together usually wants the shortest line between them — unless the board needs it to go the long way round
• Look for cells that only one colour could possibly reach; they tell you where that line has to go
• A corner cell with no dot in it has to be filled by a line turning through it