One Line - Draw It with a Single Stroke
Trace every line of the figure in one single stroke, without lifting your finger and without going over the same line twice. 240 levels, from simple shapes to mazes of arrows.
Perfect!
Choose level
How to play
- 1Put your finger (or the mouse) on any dot: that's where the stroke starts.
- 2Drag towards a connected dot: the line lights up. A lit line can't be used again.
- 3Lines with arrows can only be travelled in the direction shown; double lines must be traced twice.
- 4You win when every line is lit. To go back, drag backwards along the last line or press Undo.
What is the One Line game?
One Line (also called One Stroke) is an ancient puzzle: you have to draw a figure with one continuous line, without lifting the pen and without going over a segment twice. It's the same problem as the Seven Bridges of Königsberg, which Euler solved in 1736, giving birth to graph theory.
The trick to solve every level
Count how many lines leave each dot. If two dots have an odd number of lines, you must start from one of them and you'll finish on the other. If they are all even, you can start anywhere and you'll end where you began. Then avoid crossing a "bridge": a line that, once lit, leaves part of the figure unreachable.
All 240 levels are verified: each one has at least one solution. Your progress and stars are saved on your device, free and without sign-up.