PlaySudoku.us
Evil · Puzzle #855
8
4
6
5
1
5
9
3
3
7
1
5
6
1
9
3
3
2
6
5
7
1
8
4
9
Set theory provides the formal foundation for Sudoku's rules: each digit must appear exactly once per set.
Set theory provides the formal foundation for Sudoku's rules: each digit must appear exactly once per set.
When a box has only two empty cells, you know exactly which two digits fill them.
When a box has only two empty cells, you know exactly which two digits fill them.