My iphone 4 froze, screen turned green and turned off?

I was playing a game i regularly play when it froze. I let it sit there for a couple minutes, I pressed the home button and the screen turned green, It was green for a minute. It shut off and won't turn on. I plugged it into the charger 20 mins ago and still no response. Also, my power button broke a whille ago. What can i do? Keep it plugged in until it turns on or should i unplug it for a couple days?

Press and hold the screen lock button and the Home button at the same time for about 5 seconds.