The rule: the loop must pass straight through a white pearl (horizontally or vertically), and it must turn in at least one of the two cells immediately before or after it.
Two conditions, both required
- Straight: the loop enters and leaves the pearl’s cell on opposite sides. A white pearl has two possible orientations: horizontal or vertical.
- Turn next door: of the two cells the loop visits just before and just after the pearl, at least one must be a turn.
The three valid patterns
Once the orientation is fixed, there are three ways to satisfy the turn condition: turn after the pearl, turn before it, or turn on both sides.
The three ways to break it
The middle example catches many beginners. The turn must be in the cell immediately next to the pearl along the loop — a turn further down the line doesn’t count.
White pearls on edges and corners
A white pearl on the border can’t run perpendicular to it — the loop would leave the grid — so it must run parallel to the edge. This is one of the easiest opening moves in Masyu.
Pairs and rows of white pearls
White pearls interact strongly with each other because a white pearl is a straight cell — which means it can’t provide the turn its neighbour needs.
- Two whites in a line, loop along the line: each pearl’s inner neighbour is straight, so the loop must turn in the cells just beyond the pair.
- Three or more whites in a line: the loop can’t run along the line at all — the middle pearl would have no turn — so every one is crossed perpendicular to the row.
These patterns and more are worked through step by step in white pearl techniques.
White pearls beside black pearls
A black pearl is always a turn, so when a black pearl is the loop-neighbour of a white pearl, the white pearl’s turn rule is satisfied automatically. That’s why a white pearl sitting on a black pearl’s arm is always legal — see black pearls next to white pearls.
White pearl questions
Must the loop turn on both sides of a white pearl?
No. It must turn in at least one of the two cells directly before or after the white pearl. Turning on both sides is also allowed.
Can the turn happen two cells away from a white pearl?
No. The turn must be in a cell immediately adjacent to the pearl along the loop. If both neighbouring cells go straight, the rule is broken.
Can a white pearl be in a corner?
Not in a valid puzzle. A white pearl must be passed straight through, which is impossible in a corner cell, so a correctly made Masyu never puts one there.
Can the turn beside a white pearl be on a black pearl?
Yes. A black pearl is always a turn, so a black pearl next to a white pearl on the loop satisfies the white pearl’s turn rule.