Yeah, the original idea was a bit more than that, there were supposed to be 3 levels ( the one in game is the third, so hardest ), I also wanted to add some options, but there wasn't just enough time. As for the volume slider, i had no idea how to make it well while keeping only 2 buttons.
I have no idea why that may happen, few of mine friends played the game for quite a long time, and no one could find any bug. Can you try replaying the game and see if it still occurs?