Draw a single unbroken path that passes through every square on the board and hits the numbered checkpoints in sequence. Easy to learn in ten seconds. Genuinely hard to put down.
Free · No account · Nothing leaves your phone
Put your finger on the square marked 1 and start dragging. The line follows your finger, one square at a time.
You have to reach 2 before 3, and 3 before 4. Try to touch them out of order and the line simply refuses to go there.
The puzzle is only solved when your path covers every single square and ends on the last checkpoint. No square left behind.
Four screens, captured on a phone running the current build.
Boards aren’t just generated — they’re proven. Each one is run through a solver that stops the moment it finds a second solution, and any board with more than one gets more checkpoints until it’s pinned down to a single path.
One square. Then the next few. Then the way on towards the next number — capped, so a hint can never hand over the rest of the board. If the path you’ve drawn can’t be finished at all, it says so and rewinds you to where it went wrong.
The daily comes from the date, the weekly from the calendar week. Both are the same board for every player, so a time is worth comparing. Your streak is shown as a week, not a number, so a missed day is a gap you can see.
Classic works through a numbered ladder. Zen has no clock at all. Time Attack gives you one. The Expert Vault stays shut until you’ve earned it. The puzzle underneath never changes — only what’s at stake.
Three for a solve with no hints, two for one, one for finishing. Only your best run on a level is kept, so replaying can raise a score but never lower it.
No account, no email, no server holding your streak. A backup code carries everything to a new phone, and a checksum means a code that lost a character in a chat app is refused rather than restoring something subtly wrong.
Android only for now. The app updates itself after that — new puzzles and fixes arrive without you reinstalling anything.
Not on the Play Store yet, so Android shows a warning about installing from outside it. That warning is about the source, not the app.
The interesting part of Zolku isn't the drawing — it's that a fair puzzle is genuinely hard to produce.
Finds a Hamiltonian path — a route touching every square exactly once — using a randomised search with connectivity pruning that abandons dead branches early.
Boards come from a seeded random number generator, so the same seed always rebuilds the same puzzle. A bug report naming a seed can be reproduced exactly.
One engine, no React, shared by the phone app and the server. The hardest boards are generated and verified server-side and delivered as a pack, because an 8×8 can take seconds to solve.