@Mario D, when I played the last room didn't seem to do anything. The buttons stayed down, the door remained closed, so I figured it was the end.
You're right. When those specific buttons get shot they stay down but the solution wasn't right. The room works and the door will open when the buttons are hit accordingly, its just a bug with the buttons that makes them look visually pressed but not actually, I'm sorry about that.
The demo continues for a while after that.