Sudoku FlowSudoku technique lessons / Finned X-Wing
Lesson 30
Finned X-Wing
The rule
A fin is one extra cell on a base line that stops an X-Wing from being complete, so the candidate can be removed only from cells in the fin's box, outside the X-Wing corners and the fin, that lie on a crossing line through an X-Wing corner in that box.
Step by step
- 5 almost forms an X-Wing in two base rows. The fin is one extra cell in one of those rows that also has 5 as a candidate.
- This X-Wing sits on two base rows. We can remove the candidate 5 only from cells inside the fin's box that lie outside the X-Wing corners and the fin, and that share a column with an X-Wing corner in that box.
Try it on more boards
Each board is a real puzzle from our app, at a moment where Finned X-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.