Objective is to fillin the places with digits or symbols according to the level and pattern you select, so that you do not duplicate any symbol down any column, across any row or within any square sub-section. You get to select difficulty level by how much of the board is given you to work around; after that, it's up to you.
In the input box, you enter 3 symbols, representing row, column, and symbol to place there. Note the order of symbols in the template line at the top; some start or finish at "0".
Eg: game 4 is Hex code - "0123 4567 89AB CDEF", OMG! ends with "0", I don't think you want to know the rest yet.
YOu can enter more than one set at a time if you put a space between them - "111 122 133" will add 1 in row1 column1, 2 in row1 column 2 and 3 in row1 column3. But remember that some of these boards use letters too.
All the best, Randex Webmin.