I really like the art style and the backgrounds on each level are gorgeous. The menus and UI are all pretty polished which is great. The combat itself is good but is missing the polish of other elements. I think some hit flashes, more flashy bullets and impacts, and explosions on killing trash mobs would go a long way to making it feel a lot more exciting.
The boss battles themselves are pretty well constructed, but I think Rhyn is a bit too hard to be the starting foe. The difficulty curve felt backwards to me, it starts hard and gets easier. I'm glad you made all 3 accessible from the menu though.
My biggest complaint is the players hitbox is quite large, I dont think you have to go as far as 1 pixel hitbox but I think it's ok to be a little player friendly in these types of games, and give them a bit of leeway, some of the bullet patterns are really fast and tight and fitting a gigantic clunky hitbox through them was painful.
I really liked the card system, I wish it had a little more feedback (VFX/buff indicators etc) and was a bit more exciting to use in general. The cards are all functional and powerful but the lack of flair makes some of them a little disappointing. I'm also really upset the X beam doesn't aim!!!
Overall very good submission, feels very well made and is only lacking polish and a bit of tuning to be a really really solid finished game, great job!