Each row, column, and 3 square by 3 square section, must contain only one instance of each number from 1 to 9. Enter a digit from 1 through 9 in each cell by clicking in the selected cell.
The 'Show 1 Mistake' button above sometimes gets stuck. You may have to click it a few times to get it to work.
Clicking on ANSWERS below will fill in the entire board, so no cheating!