Sudoku Classic

10 levels of classic Sudoku, each new level more difficult. The sudoku rules apply: you can enter numbers from 1 through 9 but every number can only occur once per row, column and 9x9 box. Enter the numbers via the numeric pad on screen or your keyboard. You can delete numbers via the delete button on your keyboard or by entering the same number again via the numeric pad. The game allows you to use pencil marks. Click on the Pencil to add the pencil marks in a cell. There is a hint button that you can use for a maximum of three times per level: it shows the correct and incorrect numbers.