Sudoku is a nice game that offers three modes and three difficulty levels to choose from. The game is played in a 9x9 grid that you have to complete with numbers from 1-9 in a way that no column, row and colored area has the same number. The modes are Classic, Random and Chaos. In Classic mode the colored areas are 3x3 groups, while in Random the areas are undefined (l-shapes, lines, squares, etc) and in Chaos the colored areas are more reduced, generally to one or two cells.
The three modes are timed and you can pause and reset the game anytime you want. If you want to enter pencil markings, you need to check the test box and then enter the numbers. Unfortunately, the games cannot be saved and there are no hints or any other help options for beginners. Graphics are nice, but there are no sounds or music, which is really a shame.
In short, if you are looking for different variants of Sudoku, Sudoku may work for you. If you are a beginner, you will surely miss the hints or help options, so maybe you should look elsewhere.