Today my iPhone was working perfectly and I didn't drop it or anything. I left it turned on and put it on top of my desk. 5 minutes later I go to check on it and the screen is black. It does not vibrate when I put it on silent and when I call it does not ring. I've tried the home/off trick and it does not work. My battery was half full and I even had it charging. I also put it into my computer and nothing happened. Is it just broken?