Nice job with this -- I played it to the end! This is a very creative game, you had lots of very cool ideas for characters, play mechanisms, enemies, and bosses. The palette is really nice and your artwork is excellent. I also really liked the music. Everything tied together thematically really nicely; above all, you did a great job creating a world.
The controls took some practice, of course, as you've heard. I would also suggest you use some checkpoints -- when I would die just prior to doing everything to get the key, it was so hard to have to start all the way over. I'm one of these people who can't let it go, though, if I like the game. :) Separately, I'd also suggest using a cover image that reflects the great in-game artwork.
At the final boss there seemed to be a collider at left to prevent the player from exiting, but several times I ended up being booted back into the screen to the left, unsure if I'd been killed or could re-enter battle. Perhaps the gravestone-plant move pushes one through the collider? I wasn't sure exactly what happened, but it didn't feel quite planned.
Anyway, lots of really nice things in this game, I hope to see future games!