9x9 Sudokus bore you? Find out if you are ready for the ultimate challenge: 16x16 Sudokus. This is for highly advanced Sudoku Players only. Play 4x4, 9x9 and 16x16 Sudokus - and unlock the ultimate challenge. Touch-Screen, Trackball and Keyboard support. Pencil in functionality. Resume games where you left off. Ease to understand tutorial. Optimized for phones and tablets.