Iphone 4 stuck on black screen?

My iphone 4 is stuck on a plain black screen (still gives off some light.) I've tried doing that hold home and start for 15 seconds thing but thatdidn't work. Itunes can't detect it either.
It was also frozen on snapchat before it went black.
Its plugged into a wall charger right now but i really don't want to take it in anywhere because the closest apple store is hours away.

Added (1). I already tried hard reset

You'll have to perform a hard reset. Hold down the lock and home buttons at the same time and it should be good. All of your saved data will remain on your phone.