GridWits
Extreme tier Technique 42 of 46 Used by Smart Hint

WXYZ-Wing

XYZ-Wing stretched to four cells: a pivot plus three wings whose combined candidates match the pivot's exactly.

How it works

  1. 1A1 is the pivot, {1, 2, 3, 4}. B1 and D1 share its row and A2 shares its column, and the three wings' pairs — {1, 4}, {3, 4} and {2, 4} — combine to exactly the pivot's four digits.
  2. 2The four cells don't all share one unit: D1 sits outside the box, A2 outside the row. So this is no Naked Quad wearing a disguise.
  3. 3Digit 4 is common to all three wings. Whatever A1 turns out to be, either A1 is the 4 or the wing holding A1's value is pushed onto its own 4 — so a 4 always lands among these four cells.
  4. 4C1 sees all four — A1, B1 and D1 along row 1, A2 through the box — so its own 4 can go.

Play a Sudoku that needs this technique →

A 1 B 2 C 3 D 4 E 5 F 6 G 7 H 8 I 9 1 2 3 4 1 4 4 7 3 4 2 4 1 2 3 4 1 4 3 4 2 4 4
  • Cells that establish the pattern
  • Where the conclusion lands
  • Candidate ruled out
Next in the ladder ALS-XZ →

Two Almost Locked Sets joined by a restricted common candidate force another shared candidate into one set or the other, eliminating it from cells that see all of its holders.