I have a MacBook Air 2012 and an external HDMI monitor which I have connected. I want to use my external monitor as my main screen, but I want to use the trackpad and keyboard on the Air (so it must be open). How do I keep the MacBook Air internal screen completely off and use the external monitor? I have turned the brightness all the way down but as many of you know, it does not turn the screen completely off. I'm afraid that even if it's that dim, it's still drawing a bit of power. Any help is much appreciated, thanks!