10 VARIANTS, ONE FAMILIAR GRID
Every book plays by its own logic.
Ten distinct rule sets, from a gentle first twist on Classic to Killer Sudoku, which gives you no numbers at all — only cage sums to reason from.
Classic
Every row, column, and 3×3 box contains 1–9.
Diagonal
Standard rules, plus both shaded diagonals contain 1–9.
Windoku
Standard rules, plus four window regions contain 1–9.
Odd-Even
Shaded cells take an even number, blank take odd.
Consecutive
A bar between cells means their values are consecutive.
Alphabet
Same logic, letters A–I instead of numbers 1–9.
Mini 6×6
A smaller 6×6 grid with six 2×3 boxes. Great warm-up.
Kropki
White dot = consecutive. Black dot = double. No dot matters too.
Jigsaw
Irregular regions replace the 3×3 boxes.
Killer
No given numbers — only cage sums to reason from.