Okay, so let me give you a bit of feedback. I played for a little bit, and please don't think I'm trying to be mean throughout my feedback, I'll just be as critical as I can while being constructive as well as complementing on what you've already got so far.
Fun-ness
This game has insane potential. I love how similar it is to super smash's adventure mode, but it makes the whole idea a bit simpler and the roguelike element makes it very replayable. However, what I think you need to improve on is the visual feedback. From what I played, I got close to no visual feedback. This makes the game feel very choppy and a bit bland. From what I can tell, a simplistic style is what you're going for but you can still include particle effects and explosions while still feeling simplistic. So what I suggest you do is really try to work on and refine this, as I think your game will benefit a ton from even just the smallest of particle effects like a small trail after you walk.
Difficulty
Being completely honest, this game is brutally hard in most ways you look at it. Even in practice mode, it felt overly difficult and I found myself beating myself up constantly saying "Why am I so bad at this game??", which is not what you want your players to think. You want to make the game so easy they think they're a natural at it, and they keep playing so they can test out how good they are. You still want to leave room for challenge of course, though. So anyway, I can tell dodging is the major skill required for all of the battles I played through. This means that the modifications you made for practice mode have little to no effect on the difficulty as they based around damage and immunity frames. For this game, I would modify the amount of projectiles you need to dodge for practice mode as that would actually make practice mode feel like a practice mode like it's supposed to be. Another thing is, the game was difficult enough that I began clicking random upgrades without really thinking about it because I subconciously kept telling myself "no matter what I do, it won't make it any easier for me", which kind of ruined my experience with this game to be honest. So something you could do about this is have small tips or hints suggesting what you could buy, they could even be random, just something to awaken people from that mindset. ONE more thing for the difficulty section is also you NEED a proper tutorial. Something as simple as arrows and text saying, (go this way, follow me) that takes you down a certain path, so it doesn't leave the player confused as to where to go. One small thing as well, the ability buttons didn't seem to do anything for me.
Art
The art is interesting. Right from the start I felt like I'd been blasted by all of those intense colours. I think you need to make them less intense, or apply a filter or shader because the colour scheme just feels a little bit off. Also with the art, I like the simplistic style but it feels a little sharp and choppy. It needs to be a little smoother, but still keep the pixel art style of course so try and just make the borders and lines a little bigger.
Other stuff
The movement feels a bit strange. I understand the block-jumping style of movement but something you need to fix up is you can't go diagonal which is a bit annoying. One last thing is in the future you'd really benefit from having a storyline as I'd love to know who this weird yellow rectangle is along with the enemies you fight.
All in all, great game, keep it up! The concept is really great, and I'm loving the simplistic yet replayable style. Just make some of these changes and I think you could improve this game by a substantial amount.
And keep me updated, I'd love to see it once you make some updates to it!
And also I have one favour, would you mind checking out my game? It's called slugger and you can play it at https://slugger.surge.sh or from my itch.io profile. I'm completely remaking it in a new engine so play the original game and then check out my latest 3 devlogs about how I'm rebuilding the game. Give some feedback if you can, it really helps, as hopefully mine helped you!
Anyway hopefully I was helpful to you, and ask me anymore questions you have about my opinion on the game.
Happy game dev,
ProxyFirewall