Sounds kinda like your backlight may have burned out. Not too likely with a young machine, but possible.
Try moving your mouse up to the top left... just move it way up and left, to be sure its there. Then click... if you can faintly make out the Apple Menu being pulled down, then it would seem all is still working, but you have no backlight.
You might want to try restarting to see if it revives the backlight.
FWIW.