This is a lot more interesting than I had expected. I found myself having to take care to remind myself that most of the characters cannot jump on enemies’ heads, which can make certain sections much trickier. A charming little discovery: if you play as the Contra character, wherever there would normally be a mushroom you’ll instead find one of the Contra-style weapon powerups: laser, spread, etc. And playing in GameBoy mode is the most novel (it never popped up on its own for me in mix-it-up mode). And the warp zones are all there, of course.