Super Sudoku

Sudoku

XYZ-Wing practice

An XYZ-Wing is an XY-Wing whose pivot holds three candidates. The pivot has X, Y and Z. One wing has X and Z, the other has Y and Z, and both wings see the pivot.

One of the three cells has to be Z: if the pivot is X or Y, the matching wing is Z. So a cell that sees all three, the pivot and both wings, cannot be Z.

1 2 31 32 333
The pivot (blue) holds 1, 2 and 3, and the wings (yellow) hold 1 3 and 2 3. One of the three is 3, so the red cells, which see all three, cannot be.

How to spot a XYZ-Wing

Start from a cell with exactly three candidates and look for two two-candidate cells that see it and are made up of its numbers. The cells you can clear are few, because they have to share a box with the pivot.

Practise it on this page

The board above deals positions where the XYZ-Wing is the only way forward, with every pencil note filled in. Cross off the candidates it rules out and press Next. Press Hint to see the pattern marked on the board.

In a full game, Master is the first level that can ask for it.