PlaySudoku.us
Hard · Puzzle #313
9
6
1
4
5
3
9
6
7
5
2
3
9
8
5
1
6
3
7
4
3
2
5
8
9
8
9
4
7
3
A hidden pair in a row is often invisible until you track each digit separately through that row.
A hidden pair in a row is often invisible until you track each digit separately through that row.
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.