You want each column, row and 3x3 block to contain the numbers 1 through 9 without duplicates.
How to Play:
Yellow squares have been prefilled for you. Gray squares need you to figure out what value belongs in them. Many Sudoku players find it easier to
keep track of the possible numbers a square can contain and then continually minimize those values until one remains. To facilite that, wave your mouse
on right side of the square you'd like to put numbers in. A smaller grid of numbers will appear in the square. If you select only one number, the system
will assume that's the value that belongs in the square and put it there. If you select more than one, the system wll continue to show all the selections
until you decide which value to put in (you only have one selection left).
You can check your progress by clicking on the appropriate link. Your board will be checked against the solution. Any error on your board will be highlighted