Microsoft Sudoku is a no-frills Sudoku game with the option to play 4 different difficulty levels: Easy, Medium, Hard and Expert. Sudoku is a challenging puzzle game where each square has to be filled with the numbers 1-9. The catch is that each number can only be used once per column, row and 3x3 square. There is also an Irregular Puzzle Mode where instead of 3x3 blocks, the game uses random Tetris block-like shapes to designate the areas where each number has to be used. Toggle through the settings menu to turn on/off different options to customize the difficulty of the game to your liking. If you get stuck, there are 3 hints to use in each puzzle.