Do you think you are a sudoku master? You have 4 difficulties to choose from. Try to pass even the extremely challenging levels. Train your brain with this classic version of sudoku, improve your logic and your memory. The common rules of classic sudoku apply. Choose a square and then click on the number you want to fill. Complete the whole 9x9 game board correctly and pass the level. Use pencil mode to take notes or you can also use the hint button.