Car listen to music with light on for a while battery died

I hate to say it if the terminals were connected backwards most likely the computer got fried and who knows what else. Check all your fuses first to see if any main fuses popped. As for your computer if there are main fuses popped, replace them and if the car does not start then the computer is fried. In one situation with a fried computer, I opened it up and there was a popped prong inside, similiar to the ones you see in fuses. I sawdered it back together and put it back on the car and luckly its started back up.

Hope this Helps!