I know we have gorilla glass on the screen, but does it extend down over the buttons at the bottom? If so, how is that possible?
Yes, it's all one piece of glass, the buttons are covered. I'm not sure I understand your confusion as to how this is possible. It's a piece of glass.. that covers a tiny drawing of a few buttons..
I think the key here is that the "buttons" at the bottom are part of the capacitive surface of the phone (ie: the "touch" area of the phone doesn't have to stop at the edge of the display area).