XY-Wing

XY-Wing uses three bi-value cells arranged so each pair shares a candidate. The pivot cell sees both wing cells, and the common candidate of the wings can be eliminated from cells that see both wings.

Technique

1. Find a pivot cell with candidates {X,Y} that sees two wing cells.
2. One wing has candidates {X,Z}, the other has {Y,Z}.
3. If pivot is X, one wing is Z.
4. If pivot is Y, the other wing is Z.
5. Eliminate Z from any cell that sees both wings.

Tips

• All three cells must be bi-value (exactly 2 candidates).
• The pivot 'sees' both wings; wings may or may not see each other.
• Look for bi-value cells and check if they form the XY-YZ-XZ pattern.