Mirrored from Sudopedia, the Free Sudoku Reference Guide

# Sukaku

Sukaku is one of the Sudoku Variations. It has the same rule as a standard Sudoku, but instead of givens, the clues are presented in the form of a pencilmark grid.

Here is an example:

```.------------------------.------------------------.------------------------.
| 14789   12349   389    | 136789  1236    12479  | 3458    123469  3789   |
| 123469  15689   123578 | 124568  12346   12     | 45689   146     146789 |
| 46789   2368    1235789| 1234567 234     23468  | 2678    169     3679   |
:------------------------+------------------------+------------------------:
| 36789   1459    4679   | 2489    2578    13478  | 34      1358    679    |
| 25689   2356    379    | 1459    47      14679  | 246     358     58     |
| 4689    34567   134789 | 23568   23789   345679 | 1235679 678     126    |
:------------------------+------------------------+------------------------:
| 24678   346789  12369  | 135679  13459   256789 | 579     168     258    |
| 347     23579   3689   | 125679  1678    123459 | 135     1356    123458 |
| 1567    245789  123478 | 48      12679   489    | 38      789     156789 |
'------------------------'------------------------'------------------------'
```

The grid shows the possibilities from which to choose a digit for each cell. Where in a standard Sudoku a single placement eliminates multiple candidates, a Sukaku puzzle is more refined, since each individual candidate can be removed or left in the grid. As a result, the puzzle can be more complex than any standard Sudoku with givens.

The highest number of candidates currently known is 633. (Players's forum)

The toughness, measured in backdoor size, can be much higher than a standard Sudoku.