Black Screen

I am in the middle of a film that I rented from Itunes on my 2013 MBA. I paused it and closed the notebook to transfer it to another room. When I opened it back up the screen was black. None of the keys work and the LED light is on green. I have an Iphone and Ipad but this is my first Mac. I just got it last week and have no clue what is going on with it. I am in the middle of an assignment..help me..please. anyone..someone...I have tryed ever key. The power button won't even work.

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