The only other Mario X Castlevania's ive played Is Mario XP, and Super Mario Blue Twilight, the 2nd only being castlevania since castlevania is the final stage of the game, anyhoo im downloading this one now and giving it a try.
after playing the demo the character swap button wasn't B on my pc but N, not a big deal, im kinda wishing to see the classic stage 1 of castlevania somewhere in this game, weither its from rondo, SOTN, etc, it just seems to be on of those stages that's iconic, overall I like the original stages you've presented here, the jumps killed me more then the enemies
After seeing the soundtrack list and going threw them, I felt possibly a few of the tracks could use touching up, but im more excited since I know it wont be a short game