Okay, so, where exactly is the air intake on the MBA 2012? I know generally where the exhaust is... It seems like you can pretty much keep the machine on any surface, because the air vent(s) can't be blocked from the bottom. The screen assembly seems to block any air from moving from the bottom when the screen's open anyways... Silly question, maybe, but I like to use my notebook in bed and want to know if I need to mess with a tray... Thanks!