[centralnewyorki]

I don't know how clearly I'll explain it, but here goes...

There is a grid/box of 9 squares by 9 squares, within which are 9- 3x3 boxes. For each box, row, and collumn, you need the numbers 1-9, but the number can't be repeated in any row, box or column. You can try it out online at www.go-sudoku.com I just made myself bored with my explanation, but it's actually a lot of fun, and a great way to pass away the hours at work!