Quote from detonator300:
I noticed one flaw in the game. It's that you can't quit the demo before beating the game and returning to main menu or before closing the program from the task manager.
Did you try hitting the Escape key?
Edit: Update. I don't know why but I had music for the intro, the first stage (that's a first), and boss sound fx. I'm not sure what is going on. :-?