EXTREMEPUZZLE BOOKS

Techniques · sudoku and killer sudoku

Sue de Coq

Cells where a box meets a row or column hold a set of digits that must split between the box and the line. That rules digits out of both.

In the walkthroughs, every Sue de Coq step shades the cells of the pattern and names the cell and digit it proves, so you can see the move on the grid rather than read about it. Press “Skip to next hard step” to jump straight to it.

Worked examples

Puzzles from the books where Sue de Coq is used. Each link opens the full step-by-step solution.

Extreme Sudoku 1 (45 of 150 puzzles)

Extreme Killer Sudoku 1 (8 of 150 puzzles)

Extreme Sudoku 2 (67 of 150 puzzles)

Extreme Killer Sudoku 2 (4 of 150 puzzles)

Extreme Sudoku 3 (62 of 150 puzzles)

Extreme Killer Sudoku 3 (6 of 150 puzzles)

Where it sits

See the whole ladder on hard sudoku techniques and hard killer sudoku techniques, or look a puzzle up by number under solutions.

Cover of Extreme Sudoku 1 Extreme Sudoku 1 On sale now Cover of Extreme Killer Sudoku 1 Extreme Killer Sudoku 1 On sale now Cover of Extreme Sudoku 2 Extreme Sudoku 2 On sale now Cover of Extreme Killer Sudoku 2 Extreme Killer Sudoku 2 On sale now Cover of Extreme Sudoku 3 Extreme Sudoku 3 Out 8 December 2026 Cover of Extreme Killer Sudoku 3 Extreme Killer Sudoku 3 Out 15 December 2026