An example Non-Consecutive puzzle (no marks): touching cells never differ by 1 - every orthogonal neighbour here differs by at least 2.
Non-Consecutive Sudoku adds a single, board-wide rule and draws no marks at all: no two orthogonally adjacent cells may contain consecutive digits. Wherever two cells touch side by side - up, down, left or right - their values must differ by at least 2. It looks gentle, but that quiet rule threads eliminations through the whole grid.
The rule: touching cells jump by two or more
Take any filled cell. Each of its four orthogonal neighbours is forbidden from being one higher or one lower. A 5 in the middle of the grid, for example, blocks a 4 and a 6 in the cell above, below, left and right of it - though diagonally, consecutive digits are perfectly fine.
A 5 forbids 4 and 6 in its four orthogonal neighbours. Diagonal neighbours are unaffected.
What each digit forbids
Most digits knock two values out of every touching cell - a 5 removes 4 and 6, a 3 removes 2 and 4. The extremes are looser: a 1 only forbids a 2 (there is no 0), and a 9 only forbids an 8. That makes the middle digits the more powerful clues and the 1s and 9s slightly freer neighbours. Note too that 5 can never touch a 4 or a 6, so long runs of near-middle digits are heavily constrained.
A legal row: 2-5-3-8-6-9-4-7-1 - every neighbouring pair differs by 2 or more.
Where it shows up
The non-consecutive rule is a building block of the famous Miracle Sudoku, where it combines with anti-king and anti-knight constraints to solve a grid from just two given digits. On its own it is subtler, but the same idea drives it: every placement quietly forbids its neighbours from the two values next to it, and those small bans accumulate into singles.
Solving strategy
- Sweep neighbours on every placement. After writing a digit, cross its two consecutive values out of all four orthogonal neighbours.
- Lean on the middle digits. A 4, 5 or 6 removes two candidates from each neighbour; a 1 or 9 removes only one.
- Watch runs. Adjacent cells must zig-zag by 2+, so a line can never step 4-5 or 6-5 - use that to rule out sequences.
- Combine with the box. The neighbour bans often leave a box digit only one legal home.
Common mistakes
- Including diagonals. Only the four orthogonal neighbours are constrained; a diagonal 4 next to a 5 is allowed.
- Forgetting the extremes. A 1 forbids only a 2 and a 9 only an 8 - do not remove a phantom 0 or 10.
- Reading it as "no repeats". The rule is about consecutive values, not equal ones - repeats are already banned by ordinary Sudoku.
- Dropping the normal rules. Rows, columns and boxes still need 1-9; the non-consecutive rule is an extra layer.
Can I play it here?
Not yet - Non-Consecutive Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile:
- Try the closely related X Sudoku, which you can play right now.
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Non-Consecutive Sudoku belongs to the constraint family and runs on 9×9. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Hard Sudoku leaves 26 of the 81 cells filled, where scanning gets you started and then leaves you stranded; Expert Sudoku leaves 25, where the beginner tools dry up almost entirely. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.