XY-wing
ExpertAn XY-wing is three cells with two candidates each. The pivot holds XY. It sees two pincers, one holding XZ and the other YZ. Whatever the pivot turns out to be, one pincer is Z, so a cell that sees both pincers can’t be Z.
How to spot it
- Find a cell with exactly two candidates: the pivot, XY.
- Among the cells it sees, find one with XZ and one with YZ, sharing a third digit Z.
- Remove Z from every cell that sees both pincers.
Why it works
If the pivot is X, the XZ pincer must be Z. If it is Y, the YZ pincer must be Z. Either way one pincer holds Z.
Example
2
3
9
8
1
8
4
1
7
4
2
7
8
3
9
5
8
7
6
5
8
2
7
7
6
8
5
8
9
7
1
7
8
5
8
4
9
6
Look at these three cells with two candidates each.
Common mistakes
- Using pincers that don’t both see the pivot.
- Removing Z from cells that see the pivot but only one pincer.