Macbook air screen went black, I tried everything to fix it but it wont work

Just a few nights ago my screen to my Macbook air was on and working perfectly. I closed it and opened it again to find a black screen. I took my iphone and put the light against the screen, I could see the desktop but the brightness wouldn't work. I looked online and tried everything from resetting the computer and the power cord but nothing worked. What do i do?