About No-Lift One Line
No-Lift One Line is a free one-stroke drawing puzzle for kids. Each level is a shape made of dots and lines, and the goal is to trace the whole thing in a single unbroken stroke — never lifting your finger, never drawing over a line twice. It looks like doodling, but it is really a planning puzzle: choose the wrong dot to start from and you get trapped in a dead end.
The puzzles climb gently. Early shapes are a triangle, a square, a house, a star, with the starting dot glowing to show where to begin. As your child gets further, the glow fades and the shapes grow more tangled, so finding the right starting point becomes part of the puzzle.
How to play
- Press a dot to start. On easy levels the good starting dots glow.
- Drag through every line without lifting your finger.
- Don't go over a line you have already drawn.
- Drag backward over the last dot to undo a wrong turn.
- Lift too early and the line resets — it really is one line.
The math behind it
These are Eulerian path puzzles. Whether a shape can be drawn in one stroke depends on how many lines meet at each dot — the rule Leonhard Euler worked out in 1736 while solving the famous Seven Bridges of Königsberg, the problem that began graph theory. Your child never sees the maths, but the question they are answering — “where do I have to start so this works?” — is exactly Euler's. Every level here is checked against the rule, so each one is guaranteed solvable.
Frequently asked questions
What is a no-lift one-line puzzle?
A shape made of dots joined by lines that you draw in a single unbroken stroke — without lifting your finger and without going over any line twice. Every line must be covered exactly once. It is also called a one-stroke, single-line, or no-lift drawing puzzle.
How do you solve a one-line drawing puzzle?
Look at the whole shape before you start and pick the right dot to begin from. The trick is planning the order: a wrong early move can use up a line you needed later and leave you stranded. Trace the route with your eyes first, then draw it in one motion.
Why can some shapes not be drawn in one line?
It comes down to how many lines meet at each dot. A shape is drawable in one stroke only if every dot has an even number of lines, or exactly two dots have an odd number. More than two odd dots and it is impossible — this is Euler's rule, from the 1736 Seven Bridges of Königsberg problem that started graph theory. Every puzzle in this game is checked against that rule, so each one always has a solution.
What age is No-Lift One Line for?
Best for ages 4 to 7. The first few levels are simple triangles and squares with the starting dot glowing; the puzzles then climb steadily, adding more decision points and removing the glow so the child learns to find the start themselves.
What does it teach?
Planning ahead — looking at a whole problem and choosing a route before acting, instead of reacting move by move. It also builds fine-motor control through one continuous drag, and gives an early, hands-on taste of graph theory.
Is there a timer or a way to lose?
No timer and no score to lose. It is a thinking puzzle, not a race. A wrong move just gives a gentle wobble; lifting your finger before you finish simply resets the line so you can try a fresh route.
Is it free? Any ads or sign-up?
Yes, completely free. No ads, no account, no sign-up, and no data collected about your child's play. It runs in any browser and can be added to the home screen to play offline.
How many levels are there?
One hundred hand-checked levels that climb from a 3-line triangle to tangled webs with a dozen decision points — and then it keeps generating fresh, harder puzzles, so the ladder never ends.
Want the longer parent guide? Read: one-line puzzles for kids. Or see the full list of what each game teaches.