Sudoku FlowSudoku technique lessons / W-Wing
Lesson 23
W-Wing
The rule
Two matching bivalue cells share two candidates. A strong link on one of the two candidates, with each end seeing a different one of the cells, forces at least one matching cell to hold the other candidate, so any cell that sees both loses it.
Step by step
- The two cells marked hold only 3 and 7. In this row, 7 can go only in the two cells marked (a strong link), and each of them sees a different cell. Whichever of them holds 7, the cell it sees cannot, so that cell must be 3. This is a W-Wing!
- At least one of the two matching bivalue cells must be 3, so we can remove the candidate 3 from any other cell that sees both matching cells.
Try it on more boards
Each board is a real puzzle from our app, at a moment where W-Wing applies. Find the step yourself, or tap Hint and the app's own hint walks you through it.
Want more boards like this?
We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number.
Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.