My Samsung Galaxy S2 won't boot

[AC Question]

I have a rooted galaxy s2 GT-I9100G, installed with an Omnirom 5.1 Lollipop(Can't remember the build version). I slept while watching a movie on the phone. The next morning the phone was swithced off. I thought the battery might've died, so put it on charging. The battery icon that came up showed about 50% battery was still available. So I again tried starting it and this time it booted up to the point where the screen shows the device model no. and it didn't go ahead. I left it as it is for some time in the hopes that it might boot up after some time, but it just shut itself down after some time. Now it won't even turn on. Even when connected to a charger there is no indication on the phone that it is charging.