Very good game, with a lot of potential. Very Castlevania, in a good way.
Regarding movement and game feel, you should add coyote time to your jump because I sometimes missed an input when barely stepping off a platform. I also think you should reduce backdash cooldown to include the casty moonwalk since you have it on a stamina meter to prevent abuse anyway.
I had trouble with the first boss until i noticed that you could throw it's missiles back at it. That didn't feel very intuitive, but since I figured it out myself I feel like it could easily be fixed. Maybe you should make the boss spawn closer to the right side of the screen, because I panicked a bit on my first few attempts and tired to dodge everything instead of attacking.
Combat is mostly fine, but I hope that when you overhaul the combat mechanic you allow to cut short on endlag by walking. That would make it easier to react to enemy movement, and also make it less frustrating to deal with projectiles in a hallway.
About the UI, there are two things to say : you need to change the black text to green in dialog boxes, and you forgot to include a position indicator in menus.
And final point : I gave up on getting the stamina upgrade because enemies were too annoying to deal with.
I think that's about it, otherwise it was very fun to play and I'll definitely be waiting for the next update !