| a | b | c | d | e | f | g | h | i | |
| A | 9 | 8 | 6 | 1 | 5 | ||||
| B | 1 | 8 | 7 | 5 | 4 | 2 | 1 | 9 | |
| C | 1 | 9 | 7 | 3 | 1 | 2 | |||
| D | 8 | 4 | 1 | 3 | |||||
| E | 6 | 1 | 3 | 5 | 9 | 4 | 8 | ||
| F | 4 | 3 | 1 | 8 | 7 | ||||
| G | 5 | 1 | 7 | 6 | |||||
| H | 5 | 8 | 2 | 9 | 1 | ||||
| I | 8 | 3 | 1 | 4 |
The pattern of squares that the 1s can be allocated in row B and row C form the corners of a box. There is only one 1 in each row and column.
Stopped. Press the Play button to automatically run through the tutorial. Help page.