You said there were instructions but I couldn't see any? I worked it out anyway ^^ its fun when you know what to do. Its a great idea that with a bit more polish could be amazing! :)
I like others also thought the game was crashing, but I think the red 'X' button is still pressable even when the menu is closed? ,':/ People will instinctively click on the conveyor belt to see what it does but the game will close, making it seem like a crash - I think that may be whats happening.
For anyone wondering the interaction button is "F"