XY-Wing
AdvancedUsed at: Hard
Three cells chain through three candidate digits. Starting from the middle cell (pivot), you can eliminate the common candidate of the two wing cells.
XY-Wing Steps
1
Find the pivot
Find a cell with exactly two candidates (XY). This is the pivot.
2
Find the wings
Find two cells sharing the same row/column as the pivot, one with XZ and the other with YZ.
3
Eliminate common digit
Eliminate Z from cells that see both wings.