W-Wing
Two far-apart cells with the same pair {x, y}, joined by a strong link on x, so a cell that sees both cannot be y.
Rule
Two {x, y} cells + a strong link on x joining them → remove y from cells that see both {x, y} cells.
Two identical cells
r3c5 and r8c1 have the same candidate pair 5 and 7 but do not see each other, so they are not a naked pair.
The idea
Two cells have the same two candidates {x, y} but do not see each other. If some unit has x in only two places L1 and L2, with L1 seeing the first cell and L2 seeing the second, you have a bridge.
Suppose the first cell is not y → it is x → L1 is not x → L2 is x → the second cell is not x → the second cell is y. So at least one of the two cells is y.
How to spot it
- Find two identical bivalue cells far apart, then look for a strong link on one of their digits connecting them.
Common mistakes
- The bridge must be a strong link: a unit with exactly two places for x.
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Related techniques
References
The examples on this page are generated from random puzzles, not taken from these sources.