Unio · Free in your browser
Unio: Masyu Puzzle
Draw one closed loop through every pearl on the board
One closed loop through every pearl. Pure logic — never guessing.
The rules
- Draw one closed loop through every pearl on the board.
- Draw a single closed loop along the grid lines.
- The loop never crosses itself or branches — exactly two segments meet at every cell it visits.
- The loop passes through every pearl on the board.
- A white pearl: the loop runs straight through it, and turns in at least one of the two cells next to it.
- A black pearl: the loop turns at it, and runs straight for at least one cell on both sides.
- Only two mistakes are pointed out as you play: a cell where the loop branches or crosses itself, and a small loop that closes early without every pearl. A pearl rule broken on its own is not marked until the board is checked as a whole — so a full loop with no warnings on it can still be wrong.
- Drag between cells to draw the loop. Tap a segment to cross it out, once more to clear it.
- Every puzzle here is solvable by reasoning alone. You never have to guess.
- Got it
How to play here
Three ways to play
Campaign
Chapters that start gently and bring in one new idea at a time.
Daily puzzle
A new board every day, the same for everyone. Solve every one in a month and that month's trophy is yours.
Endless
Keep going as long as you like, in Easy, Medium, Hard and Expert.
About the game
Unio is a Masyu puzzle — a loop drawn through pearls — for players who like unhurried, honest logic.
There are no numbers anywhere. You draw one single closed loop through the grid, and it has to pass through every pearl on the board. At a white pearl the loop runs straight through and turns just before or just after it. At a black pearl the loop turns, and runs straight for at least one cell on both sides. That is the whole game.
Never a guess
Every puzzle has exactly one solution, and every step of it can be reasoned out. Each board is verified by a solver that only uses techniques a person can follow and explain — so a puzzle that would need trial and error never ships. The hint button uses that same solver, which means a hint is always a move you could have found yourself, and it tells you which idea it used.
Learn it by playing it
Two pearls and two rules are quick to read and slow to see. The walkthrough hands you real positions and asks for the one segment that follows, then shows you why. No board in it was made up — each is a genuine puzzle stopped at the moment the idea it teaches becomes the forced next move.
Three ways to play, all offline
- 12 campaign chapters, from gentle openings to genuine work
- A daily puzzle, the same one for every player worldwide, with a gentle Monday and a demanding Sunday
- Endless mode in four difficulties: Easy, Medium, Hard, Expert
Measured in months, not streaks
Fill in every day of a calendar month and the month earns its own trophy. There is no streak to lose: a day you missed can still be filled in from the archive, so a week away from the game costs you nothing.
Built to be pleasant
- Warm Material 3 design, light and dark, following your system colours
- Completely offline — no account, no sign-in, no network needed
- Boards shaped for a phone held in one hand
- No countdowns you did not ask for and no interruptions
27 languages supported. No account required. Pure logic.
Common questions
Is Unio free?
Yes. You can play here without paying and without an account. Ads keep the lights on.
Where is my progress saved?
In this browser, on this device. If you clear the site data, your progress goes with it. A free Solvarium account keeps it safe.
Does it work on a phone or tablet?
Yes. It runs in any current browser on phones, tablets and computers, and the board resizes to fit the screen.
Does every puzzle really have one solution?
Yes. Every board goes through a solver before it ships, and anything with more than one solution is thrown out.