CLASSIC RULES
Sudoku Rules
Fill all 81 cells so that each row, each column and each outlined 3×3 box contains the digits 1 to 9 exactly once.
Givens cannot change
The starting digits define the puzzle and remain fixed.
No arithmetic required
Digits are symbols in Sudoku. You do not add, subtract or calculate them.
One logical solution
Sudoku Genius validates its included catalogue so each puzzle has one intended solution.