I liked it even though I'm not a big fan of 2d platformers or castlevanialike games. I really like the art style and the music is really good, I'd say both are on point. My only criticism would be the game being too dark and it's hard sometimes to tell the platforms apart, I even raised my tv brightness up a lot but it didn't fix it.
One thing I think the game is missing is the ability to jump down platforms by pressing down and then jumping to drop down. I tried that but I don't know if you can do that in the game yet but I think that would be a nice feature to have.
I climbed up the tower(?) where you have a breakable wall and got stuck there, it took me a while to realize you had to jump over the ceiling on the platforms. Maybe it's just me not paying enough attention or maybe you could make it a little bit more obvious that you have to go up there because I legit thought that was the ceiling and that's it. I haven't finished the demo yet now that I found my way up the tower so I'll play it more later. Either way I'm looking foward to your game.