The game of Sudoku can be very simple and it can be complex. The rules state that you should use the numbers 1 to 9 in every 3x3 grid without repeating the numbers and then use them in the rows and columns of the 9X9 grid with no repetition. This is a concept that boggles the mind, but it does work. This is the appeal behind the game; players are just amazed when they finally complete a puzzle. Sudoku is not about guessing and every puzzle and its solutions are unique. The best way to approach a Sudoku game is to check the rows and columns and then see where the numbers fall in the 3X3 grid. 3D Sudoku gives you the chance to select the level of difficulty that you would like to try; these are Easy, Medium, Hard and Very Hard. This is a great game for anyone who wants to learn how to play Sudoku. When you place a number in a box that is not allowed, the numbers that are stopping this placement will blink in red. If you are placing the number 4 on a row, column or 3X3 grid which has a number 4, then this number will blink. Anyone who has never played Sudoku will appreciate this kind of action. The game is timed so you may know how long it took you to complete the puzzle. You can pause it if you want to take a break. You can also print the puzzle if you want to do it on paper. Click on any of the numbers at the bottom of the game and then click in any of the boxes so you can fill them with the number. This is a great free online Sudoku game and you will have plenty of fun playing it.