Sudoku-YAdvanced
XYZ-Wing: the target must see all three cells
The name resembles XY-Wing, but its target needs an extra connection. The case split shows why.
One pivot, two wings
A pivot {x,y,z} sees wings {x,z} and {y,z}. At least one of these three cells contains z. Remove z from another cell only when it sees all three through ordinary Sudoku units.
Our original partial scenario
Use B2={2,5,8}, B5={2,8} and C3={5,8}. B2 sees B5 through row B and C3 through the top-left box. Target B3 sees all three.
- B2=8 directly blocks 8 at B3.
- B2=2 forces B5=8.
- B2=5 forces C3=8.
These cover every pivot candidate. Each case places an 8 visible to B3, so B3 cannot be 8. This is a partial scenario, not a complete puzzle.
Why C5 is not a target
C5 sees B5 by column and C3 by row, but does not see B2. With B2=8, B5=2 and C3=5, the three cells do not block 8 at C5. Seeing only the wings is insufficient here, unlike an XY-Wing whose pivot lacks the eliminated digit.
Adding candidate 9 to B5 also breaks the stated pattern: B2=2 would no longer force B5=8.
A useful self-check
Ask who blocks the target when the pivot itself holds z. The answer should be the pivot. If the target cannot see it, choose a different target instead of applying the elimination.
In Classic 9×9, use Scan to scan the current entries, inspect justified eliminations and open this lesson. Chain and ALS searches are bounded; UR Type 1 and BUG+1 require verified uniqueness. Reading this lesson never changes your saved game.
Try before looking
Try before revealing
B3 sees all three cells, but B5 has {2,8,9}. Does this XYZ-Wing still work?
Show explanation
Not with these premises. When the pivot is 2, B5 could be 9 instead of supplying the required 8.
References and further reading
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