Sudoku Strategy: XY-Wing
XY-Wing is a more complex chain-based strategy that helps eliminate candidates using three interlinked cells.
How It Works
You need three cells:
- Cell A with values {x, y}
- Cell B with values {x, z}
- Cell C with values {y, z}
If A sees both B and C, and B and C each share one candidate with A, then the value common to B and C can be eliminated from other cells that see both B and C.
When to Use It
- Expert puzzles where naked/hidden techniques no longer work
- You notice chains of two-candidate cells
Practice XY-Wing
Need more firepower? Try Swordfish next — it's like X-Wing's big cousin.