Hey I just saw your message, too bad I haven't seen it earlier, I just spent some time play testing the alpha 4 version in 2P and took screenshots for you

I'll try the beta 1 when I come back and let you know if I find anything else.
Just in case, on the alpha 4, I found this ;
- there are different black colors, a full black and a lighter black, on the 2P win/loose screens
- when the music speeds up, Mario moves his hand in the back and it turns yellow. I also think there are a couple pixels that probably shouldn't be here on this sprite between his hip and yellow hand.
I also don't think the music issue is important, I just wanted to inform you

Thanks again, it's great !