Apple II Sudoku is a sudoku interpretation for Apple II systems. Follows typical sudoku rules. There is a 3 x 3 square consisting of smaller 3 x 3 squares. The players must put the numbers 1 - 9 into each small square, so that each number is used only once per square, as well as used only once in a vertical and horizontal line. Controlled via the keyboard, there are three levels of difficulty. Players have the option to allow incorrect or invalid values to be flagged.