I have a Trackball Assembly with USB interface. The trackball and one button work great in mame4all playing centipede. I'd like to configure the other two buttons to be 1 player/2 player buttons. But I'm lost.

I'd use AdvMAME but I not sure how to configure it either.

I have a couple other questions but they are about rotating the screen and then getting it to stretch to the screen correctly, but one problem at a time.