I want to say I really like the artwork and effort that's been put into this. Attaching an artbook to go along with the game is a really nice touch.
The music once you actually get into the game is really good it just felt a little odd that there's no audio at all until you actually get in.
To be honest it's a little rough around the edges and clearly needs a bit more time to finish up properly. There's no real feedback on whether you or the enemy gets hit by an attack at all. It took me like 20 seconds to even realise I was doing damage to the boss at all before I noticed the health bar on the bottom right going down.
The actual concept itself of fighting while dodging stuff on the disc that's spinning around is really cool and I could tell while playing that it could be fun.
Somehow I managed to clip off the side of the disc and wasn't able to get back on so I had to restart the game.
When I defeated the vampire boss the game just stopped giving me new bosses so I'm not sure if that means I won or if it just bugged out somehow. I also noticed quite a few effects where the enemy just had a big default square attack and a few of the particle effects didn't look finished.
A custom font and UI elements for the buttons at the start of the game would go a long way as well. You've already got custom UI for a lot of other elements so it would tie it together well.
Overall It's a good concept and I would like to see it fully realised with more time!