The rules are simple: Enter the missing numbers in the empty squares in the grid so that the number 1-9 occur ones, and only ones, in each row, column and group.
Here's an example. Take a look at the bottom right group of the grid below and try to find a location for the number 8. There's only one square were the 8 could be placed, the square marked with green. All the red squares are forbidden because of the placements of the other 8's marked with blue.
| 9 | 5 | |||||||
| 1 | 9 | 6 | 2 | |||||
| 5 | 8 | |||||||
| 7 | 8 | |||||||
| 3 | 8 | 9 | ||||||
| 1 | 9 | 3 | ||||||
| 9 | 8 | 1 | 6 | |||||
| 5 | 6 | 3 | 8 | 7 | ||||
| 4 | ||||||||
| © 2006 Patrik Kudo | ||||||||
|---|---|---|---|---|---|---|---|---|