Advanced

Finned Fish

When an almost X-Wing has extra candidates in one box.

Explanation

A Finned Fish is a near fish pattern with one or more extra candidates called fins. If the fins are false, the fish works; if a fin is true, it still removes candidates that see every fin.

Finned Fish example Sudoku board 7 9 3 5 4 2 8 6 5 2 3 4 8 9 1 7 2 9 5 6 5 8 9 2 3 1 6 9 6 3 8 4 2 6 5 9 2 8 5 1 6 3 4 3 7 2 8 6 9 6 9 4 3
An example board where Finned Fish applies

Practice tip

Start from X-Wing shapes. When one box has extra candidates, only delete cover candidates that also see all fins.

Example steps

  1. Pick one candidate and find a near X-Wing.
  2. Confirm the extra candidates all sit in one box.
  3. Remove only the cover candidates that see every fin.

Try this technique on a real puzzle.

Play Sudoku Online