Why did my screen go dark?

i was playing words with friends and my screen got dark,where i could barely see it..i rebooted it and it brightened the screen again.about 5 minutes later it went dark again. i went on settings and looked to see brightness was still set i turned it off then back on again.. still dark ..what is this trying to tell me is there a lose connection or is there a bulb that is burning out,is there a quick fix???