The system's touch screen makes choosing or writing numbers easy. Players will find more than 400 puzzles, all of which were selected by the original creators of sudoku. Sudoku is the most popular puzzle game in the world right now, and Sudoku Gridmaster puts hundreds of puzzles in portable form, just in time for the summer travel season. To satisfy novices and sudoku experts alike, the puzzles come in four difficulty settings: practice, easy, normal and hard. Sudoku Gridmaster is Rated E for Everyone.