XY-Wing
XY-Wing · Y-Wing
A pivot {x, y} sees two pincers {x, z} and {y, z}, so a cell that sees both pincers cannot be z.
Rule
Pivot {x, y}, pincers {x, z} and {y, z} → remove z from cells that see both pincers.
Pivot and pincers
The pivot r2c8 has exactly two candidates 4 and 6. It sees two "pincers": r9c8 (4, 9) and r2c5 (6, 9).
The idea
It uses only bivalue cells. The pivot holds {x, y}; it sees one pincer {x, z} and another pincer {y, z}.
If the pivot is x, the first pincer loses x and becomes z. If the pivot is y, the second pincer becomes z. There is no third option, so one pincer is certainly z. Any cell that sees both pincers cannot be z.
It is the first three-step chain most players learn: assumption → consequence → consequence, packaged as a pattern you can spot at a glance.
How to spot it
- Mark the bivalue cells. Pick one as the pivot, then find two cells it sees that each share exactly one digit with it and share a third digit z with each other.
Common mistakes
- The pincers don't need to see each other, but both must see the pivot.
- Only z is eliminated, never x or y.
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Related techniques
References
The examples on this page are generated from random puzzles, not taken from these sources.