Sashimi X-Wing

Level 9 · Purple Belt

Strategy:

Finned & Sashimi Fish

Overview

Sashimi X-Wing is a variant of Finned X-Wing where one of the base cells is missing. The pattern still allows eliminations in cells that see both the fin and the expected elimination zone.

How It Works

  1. Find an almost-X-Wing where one row is missing a candidate in one of the expected columns.
  2. The missing cell creates a 'sashimi' pattern - the fin compensates for the gap.
  3. The fin must be in the same block as the missing cell's expected position.
  4. Eliminate the candidate from cells seeing both the fin and the cover column.

Example

Starting position

Look for Sashimi X-Wing.

1

Columns 6 and 9 form a X-Wing on 7

Base columns 6 and 9 form a X-Wing for digit 7 in cover rows 3 and 5.

2

7 is blocked from r2c6 by the row

Digit 7 cannot go in r2c6 because r2c1 is already in this row. Remove the entry or choose a different digit.

3

r4c6 is already filled

r4c6 is already filled with 6.

4

r6c6 is already filled

r6c6 is already filled with 8.

5

7 is blocked from r7c6 by the row

Digit 7 cannot go in r7c6 because r7c4 is already in this row. Remove the entry or choose a different digit.

6

r8c6 is already filled

r8c6 is already filled with 5.

7

r9c6 is already filled

r9c6 is already filled with 4.

8

r1c9 is already filled

r1c9 is already filled with 2.

9

7 is blocked from r2c9 by the row

Digit 7 cannot go in r2c9 because r2c1 is already in this row. Remove the entry or choose a different digit.

10

r4c9 is already filled

r4c9 is already filled with 1.

11

r6c9 is already filled

r6c9 is already filled with 5.

12

7 is blocked from r7c9 by the row

Digit 7 cannot go in r7c9 because r7c4 is already in this row. Remove the entry or choose a different digit.

13

r8c9 is already filled

r8c9 is already filled with 4.

14

r9c9 is already filled

r9c9 is already filled with 9.

15

The fin sits in box 2

One base column has extra candidates in box 2. That box is the fin, making this a Sashimi X-Wing.

16

Only box 2 can lose 7

Because of the fin, only cells in box 2 that also lie in rows 3 and 5 can lose digit 7.

17

Cells that see both fish and fin

These cells see both the fish structure and the fin, so they are removal targets: r3c5.

18

Remove 7 from the fin-affected cells

Remove 7 from these fin-affected cells: r3c5.

19

Result

Result after applying the technique.

Tips & Patterns

  • Sashimi fish are related to finned fish but with a missing base cell.
  • The eliminations are identical to the finned version.
  • If you understand Finned X-Wing, Sashimi follows the same logic.