This is a classic game of Sudoku where you just fill in the numbers 1 to 9 in a 3X3 grid and make sure that the numbers are not repeated. Then you have to make sure that the 9X9 grid does not have any of the numbers repeated in any of the columns or rows. This is the simplest form of Sudoku that there is and it can be a great starting place for people who have no idea how to play. However, even if it is the classic game, there are a few features that have been added so that the game can be a little more challenging to you. You have to finish the game in 20 minutes; there is a timer on the left side of the game and you should keep your eye on it. If it gets to zero and you have not completed the puzzle, then you will have to start all over again. Another special feature is the fact that you do not have any hints and you have to earn them; as you go on solving the puzzle, you start earning hints which will be useful to you if you get stuck in the game. To fill in a square, you have to click on it and a pad will appear and you can add the number. You can also erase the number in the same way but you use the X at the bottom of the pad. When you click on the small white box, you will be able to use the pencil method and add possible candidates for the square. This is an amazing game and one which can be great for training purposes. It helps you understand several methods of solving Sudoku; the game will keep you engaged and at the same time entertained.