Quick answer: In Masyu you draw one closed loop through the centres of grid cells. The loop must pass through every pearl. It turns on every black pearl and goes straight through the cells on both sides of it, and it goes straight through every white pearl while turning in at least one of the two cells next to it.
The goal
A Masyu puzzle is a rectangular grid — usually square, from 6×6 up to 25×25 or larger. Some cells contain a white pearl (an open circle) and some contain a black pearl (a filled circle). Your job is to draw a loop that visits every pearl while obeying the pearl rules. A well-made Masyu has exactly one solution, and you can always reach it by logic.
Rule 1 – Draw a single closed loop
The loop is made of straight segments that join the centres of neighbouring cells, horizontally or vertically — never diagonally. Every cell the loop visits is entered once and left once, so each turn is exactly 90°.
- There is exactly one loop, and it closes back on itself.
- The loop never branches (no T-junctions) and never crosses itself.
- The loop doesn’t have to visit every cell — empty cells can be skipped.
Rule 2 – Black pearls: turn, then go straight
When the loop reaches a black pearl it must turn 90° on it. In addition, both of the segments leaving the pearl must travel straight through the next cell. In other words, a black pearl is the corner of an “L” whose arms are at least two cells long.
Rule 3 – White pearls: go straight, turn next door
The loop must pass straight through a white pearl, either horizontally or vertically. It must also turn in at least one of the two cells directly before or after the pearl. It may turn on both sides.
Black pearls are bends; white pearls are straights. Each pearl also pushes the opposite behaviour onto its neighbours: a black pearl’s neighbours on the loop go straight, and at least one white pearl neighbour on the loop turns.
Common beginner mistakes
- Closing a small loop too early. Any loop that doesn’t include every pearl is wrong. If two loose ends sit next to each other, joining them is only allowed when it finishes the whole puzzle.
- Short black-pearl arms. Remember the arm passes straight through the next cell — the turn can happen two cells away at the earliest.
- Forgetting the white pearl’s turn. A row of three straight cells centred on a white pearl is never allowed.
- Guessing. Every puzzle here can be solved logically. If you’re stuck, look for edges you can rule out with an ✕ — they’re just as useful as lines.
Worked example: solving a 6×6 Masyu
Let’s solve the puzzle from the top of this page. New lines in each step are shown in green.
1 Corner black pearls
A black pearl in a corner has only one way to turn: both arms must run along the two edges, two cells each. All four corners here hold black pearls, so we can draw eight arms immediately.
Notice that both white pearls on the edges, at the left and bottom, are already satisfied: each is passed straight through, and each sits next to a corner where the loop turns.
2 The black pearl on the right edge
The black pearl in row 3 on the right edge can’t send an arm to the right because it would leave the grid, so its horizontal arm runs two cells to the left, ending on the second black pearl. Its vertical arm is the one coming down from the top-right corner.
3 The two white pearls in the middle
Could the upper white pearl run horizontally? Then the loop would continue straight into the black pearl on its right — but that black pearl is already entered from the right and can’t be passed straight through. So the white pearl runs vertically, and since the white pearl below it is entered from above, it runs vertically too. Both white pearls now need a turn beside them, so the cells just above and just below this column must turn.
4 Which way does the inner black pearl turn?
Suppose the inner black pearl turned upward. Its arm would reach the top row and take the last free exit of the top-right segment, so the end of the top-left segment would be forced straight down into the cell above the white pearls — where the loop must turn. That’s a contradiction, so the black pearl turns down. That same argument now forces the two top segments to join.
The cell above the white pearls must turn left or right. Turning right leads into a cell boxed in by existing lines — a dead end — so it turns left.
5 Finish the loop
Now only a few loose ends remain. Connect them without creating dead ends or closing a small loop. On the left, the new turn above the white pearls drops down to meet the left-edge arm; below the white pearls the loop turns left and climbs back to the left edge; and on the right, the inner black pearl’s lower arm zig-zags across to meet the right-edge arm. The loop is complete — and it is the only one possible.
Those moves — corners and edges first, then pearl interactions, then contradiction checks and loop-end logic — are the core of every Masyu. The strategy guide covers 15 such patterns in depth.
Playing Masyu on this site
| Action | Mouse / trackpad | Touch screen | Keyboard |
|---|---|---|---|
| Draw a line | Click and drag across cells | Drag your finger across cells | Shift + arrow |
| Erase a line | Drag back over it, or start a drag on a line | Same as mouse | Shift + arrow on a line |
| Mark ✕ (no line here) | Right-click an edge or right-drag | Tap an edge twice, or turn on ✕ mode | Alt + arrow |
| Undo / redo | Toolbar buttons | Ctrl+Z / Ctrl+Y | |
| Hint · Pause · ✕ mode | Toolbar buttons | H · P · X | |
Pearls glow green when their rule is satisfied, and red markers flag any rule you’ve broken (you can switch both off in Settings). Your progress saves automatically.