The aim of Sudoku is to fill a 9×9 grid with numbers so that each column, row and nine 3×3 sub-grids contains all the numbers from 1 to 9. In order to accomplish this, you need to place numbers ranging from 1 to 9 into the empty fields. Depending on your preferences, you can use either the mouse or your keyboard to play. You can also select the difficulty, depending on how skilled you are in Sudoku. There are three levels of difficulty: Easy, Medium and, if you feel up to the challenge, Hard. If you make a wrong move, you can use Undo to remove the latest added number or you can Restart the whole game. Don’t have time to finish the game now, but you don't want to start over next time? No problem, you can Save the game and later on Restore the saved game when you like. And if you get stuck, you can use a Hint.