PlaySudoku.us
Hard · Puzzle #988
1
8
9
6
8
2
4
3
7
2
5
6
3
8
1
4
7
5
2
8
6
9
2
1
3
4
8
2
9
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.