XYZ-Wing
A three-candidate cell links to two two-candidate cells whose combined candidates match it exactly — the shared height can't be in any cell all three see.
The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.
How it works
- 1An XY-Wing whose pivot keeps a third candidate: {1, 2, 3} here, with wings {1, 3} and {2, 3}.
- 2Now the pivot itself might be the 3, so the guarantee widens: one of the THREE cells is a 3, not just one of the two wings.
- 3That means only cells seeing all three can be eliminated from — and here all three sit in one row, so those are the row's remaining cells. Strike their 3s.
- 4Worth knowing the limit: Skyscrapers has no boxes, only rows and columns. Work it through and a common peer of all three exists only when all three share one line — and three cells in a line covering three heights is a Naked Triple, which this guide lists as easier and which strikes all three heights rather than just the shared one.
- 5So in practice the Naked Triple gets there first. The shape is here because you'll recognise it from Sudoku, where boxes give it room the Skyscrapers grid doesn't.
- Height ruled out
- Relationship — The arrow shows which cells support the deduction.
- Conclusion — The final arrow lands beside the proved or ruled-out height.