The screen itself is a button, so it moves :) Dont worry, it was designed that way :) Looks like it was a bad design choice, but unfortunately one that went to the production line. They wanted the haptic feedback to be more "responsive". 

It's supposed to move :) I know thats weird, but I've played around with one for a bit and it does feel like something is wrong, but my friend says you'll get used to it.