2 bugs to report.
1. Turning Fullscreen off isn't saved, so the game automatically goes back to fullscreen whenever you re-enter.
2. It looks like a few puzzles get "removed" after a game is played/exited. I've provided a video showcasing this, where the number of puzzles available goes from 125 to 118. Restarting the game brings back the "removed" puzzles, at least.