Techniques / Wings
W-Wing
Two identical bi-value cells joined by a strong link on one of their digits.
Two cells with the same two candidates {X,Y} that do not see each other, plus a unit where X has exactly two candidates, one seen by each bi-value cell. If one bi-value cell is X, its linked cell in the unit is not X, so the other end of the strong link is X, which makes the second bi-value cell Y. Otherwise the first cell is Y. In both cases at least one of them is Y.
Remove Y from every cell that sees both bi-value cells.
Notation
W-Wing: 1 can be removed from r4c8.
pattern fin / link removed
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