W-Wing

Level 6 · Orange Belt (Green Stripe)

Strategy:

Wings

Requires:

Naked Pair

Overview

W-Wing consists of two identical bi-value cells connected by a strong link on one of their candidates. The other candidate can be eliminated from cells that see both bi-value cells.

How It Works

  1. Find two bi-value cells with identical candidates {X,Y} that don't see each other.
  2. Find a strong link on digit X (or Y) connecting cells that each see one of the bi-value cells.
  3. If the strong link is on X, eliminate Y from cells that see both bi-value cells.

Example

Look for W-Wing.

1

W-Wing

Find two bivalue cells with identical candidates: r2c8 and r8c7 both have { 3, 5 }.

2

W-Wing

These cells don't see each other, but are connected by a strong link on digit 3.

3

W-Wing

The strong link is at r2c2-r8c2. If neither bivalue cell has 3, the link forces a contradiction.

4

W-Wing

Therefore, one of the bivalue cells must be 5. These cells that see both cannot keep 5: r3c7.

5

W-Wing

Remove 5 from the cells that see both bivalue cells: r3c7.

6

Result after applying the technique.

Tips & Patterns

  • W-Wings are relatively easy to spot once you know the pattern.
  • Look for matching bi-value cells first, then search for connecting strong links.
  • The elimination digit is the one NOT involved in the strong link.