Things that have improved:

- Confirmation prompts were implemented for saving, loading and clearing the puzzles.
- Given numbers are now thicker than numbers placed by the player.
- Aspect ratio issues have been obliterated by windowing the game.
- It's now clear that the clear puzzle button clears the puzzle.
- Pause/Play icons were swapped.

Things I want to improve but still don't know how:

- Incorrect filling warning not only when the puzzle is filled.
- Build the game for Linux and Mac