Game guide
How to play One Line
In One Line you trace every line of a drawing in a single stroke, never repeating one. It is the old puzzle of drawing a figure without lifting your pencil, in ever larger levels.
Updated on October 5, 2026
The rules in 3 lines
- 01
Every line
A level ends only when all the lines of the drawing are painted.
- 02
None repeated
You cannot go over the same line twice. Dots, though, can be visited as often as you like.
- 03
One stroke
Each segment starts where the last one ended. Stuck? Undo or restart.
How to play
On your phone
- Drag your finger from dot to dot. The line paints when you reach the neighboring dot.
- Or tap a dot to start, then tap its neighbor.
- Going back to the previous dot undoes the last segment. Undo, Restart and Hint sit below the drawing.
- The “Level” button at the top opens the level list.
On a keyboard
- ← ↑ → ↓ move between dots.
- Enter or Space picks the dot (starts there or moves to it).
- Backspace undoes the last segment.
Step-by-step example
The secret is in the dots that an odd number of lines reach. If there are two of them, the stroke must start at one and end at the other.
Start
Halfway
Done
Beginner strategies
- Count the lines at each dot. A dot with 1, 3 or 5 lines is odd: start at one of them. If none is odd, any dot works and the stroke ends where it began.
- Use the Hint. It restarts the level and marks the possible starting dots in gold.
- Do not trap yourself early. Before entering a part of the drawing with a single way out, finish what you left behind.
- Save bridges for last. A line that is the only link between two parts of the drawing should only be used when there is no other choice.
Common mistakes
- Starting at an even dot. If there are odd dots, starting anywhere else always leaves a line behind.
- Pushing on after a dead end. “Dead end” means there are lines you can no longer reach. Undo a few segments.
- Thinking each dot counts only once. Dots can be revisited; only lines cannot.
Levels and scoring
The levels never run out: the drawing grows from 5 lines on a 3×3 grid of dots to more than 20 lines on a 5×4 grid. Every level has a solution, and level 12 is the same for everyone. Each level unlocks when the previous one is done; your best is the number of levels completed.
Frequently asked questions
Yes. The drawing is built from a stroke that already covers every line, so there is always a way.
It is almost always the starting dot. Start at a dot with an odd number of lines, or use the Hint.
Completed levels are saved on this device. A level left halfway starts over.
It is: it is the Euler path problem, the one from the bridges of Königsberg. But playing makes you better at this game; it does not change your IQ.
IQNorth games are a pastime with a challenge. Practice makes you better at this game; it does not raise your IQ or your memory, and nothing here is a consultation with a psychologist. The games are in the member area.
Guides for the other games
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