I always have to go back to Genesis Plus GX for the game to play properly, but I only have Genesis Plus GX because I installed it a long time back before upgrading to 3.8. I ran this test when I originally upgraded to 3.8, and again today with the Feb '21 release of this core. With Genesis Xtreme GX the game initially looks fine, but you quickly realize the graphics are wonky and a bit jumpy, like its trying to do some kind of interpolation/smoothing, and also that some of the sound effects don't even play. With Genesis Plus GX it works and sounds great. So I've tried this new Xtreme core a couple of times now (I just updated to 3.9.1 and latest retroarch and cores today). I think maybe in version 3.8 it was replaced with Genesis 'Xtreme' GX and plain old Genesis Plus GX was missing. I originally hacked my Genesis Mini with hakchi ce 3.7 I think and installed the Genesis Plus GX core for my additional games, because its a good core and the music sounds much better than m2engage (to me). Not a sophisticated user here, just trying to understand what is going on.