If the number is correct, the sudoku tile will slide into its correct slot. If not, the number will return to the outside and time will be added to your overall sudoku game time. To highlight numbers, click a number that has aready been placed inside the sudoku puzzle. As the game progesses, you may want to use notes. Click the pencil in the right bottom corner to turn the numbers into notes. Just click it again to return to puzzle number form.