Difference Sudoku
Circles mark neighbours whose digits differ by 1.
Also known as Consecutive Sudoku, Touchy Sudoku.
How to play Difference Sudoku
- Standard 9×9 sudoku: 1–9 exactly once per row, column and 3×3 box.
- A circle on the border between two neighbouring cells means their digits are consecutive — they differ by exactly 1.
- Every consecutive pair is circled, so a plain border means those two digits are *not* consecutive.
Where to start
A circle beside a 9 forces an 8 — there is no 10.
Difficulty
Puzzles are generated on your device, so there is an endless supply of them. Difference Sudoku comes in 2 grades — or work up the endless track, where every level is generated a little harder than the last.