PlaySudoku.us
Hard · Puzzle #429
2
7
3
1
3
7
8
4
8
6
9
6
2
3
4
5
1
1
4
2
4
6
6
1
3
9
3
8
4
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.