Sudoku Genius

The game generates random sudoku puzzles, for any of five levels of difficulty you want.
Make each row, each column and each 3x3 square contain all numbers, from 1 to 9 once.
Select the square first and then the number, you want to write in it.
Press the 's' button to inverse this order.
Press the 'n' button to keep notes.
Press the empty button to empty the square.
When you achieve to finish the puzzle, fill in your name, to keep track of your high scores.