Sudoku game on pygame

This is an implementation of the logical sudoku game. The goal of the game is to fill the entire field with numbers from 1 to 9. Rules of the game: • numbers should not be repeated in a line; • numbers should not be repeated in a column; • numbers should not be repeated in a small block (square 3 by 3); To cancel the entered number, enter 0 instead. To navigate the cells using the arrows on the keyboard. Also added autosave of the current game when closing. The next time the game starts, it automatically loads the save. Added ability to change difficulty level.