Box Brain Sudoku
Learn › Swordfish
Expert · technique 18 of 18
Swordfish
An X-Wing stretched over three rows and three columns.
How it works
If a digit's places in three rows all fall within three columns, remove it from the rest of those columns.
A worked example
Swordfish: 6 appears in row 1, row 2 and row 4 only within 3 columns, so 6 is removed from those columns elsewhere.
- The rows and columns to look at
- The cells that make the pattern
- Candidates it rules out
A real position from a puzzle in the app. Small digits are the candidates the step looks at; coloured digits are already solved.
Practise it in Box Brain Sudoku
The app teaches Swordfish on this same board, then hands you puzzles that need it. When you are stuck mid-game, a hint first points you to the right area, then names the technique and shows the move.