W-Wing
Advanced Logic26 / 32Twin cells linked by a strong wire.
Two cells in different units holding the identical candidate pair {A,B}, plus a unit in which digit B has exactly two spots — one seeing each twin. That strong link wires the twins together.
Try to make both twins B: the wire's ends are then both blocked, but the wire's unit needs its B somewhere in those two spots. Contradiction — so at least one twin is A, and cells seeing both twins drop A.
See it in action
Step 1 of 4
The setup
Collect pairs of identical bivalue cells that don't see each other. For each pair, hunt for a row, column or box where one of their two digits has exactly two spots, one next to each twin. Step through this real position to see it happen.
Practice
Find the W-Wing and remove the twins' other digit from their common peers.
Drill 1 of 29Tap a cell, then the candidate digit you want to remove.