You definitely get all the points for style and creep factor, and overall it was fun enough for me to finish it, but the controls and level design could use some fine-tuning. Normally when a game has a fixed jump like this one, it's entirely fixed, i.e., the direction is set as soon as you hit jump *and* the height is consistent. Think Super Ghouls and Ghosts, if you've ever played that. The consistency makes it a lot easier to plan out and control your jumps, which is important when the character also doesn't maintain forward momentum if they hit a wall. This hybrid style where the arc is fixed but the height isn't is kind of awkward and unintuitive. It wasn't a deal-breaker, but it sapped a little of the fun out of it.
Additionally, randomizing the enemies that spawned in places when you die made the castle more frustrating. I'm thinking specifically of the section where you had to wall jump back and forth three or four times to climb a vertical shaft. If the enemy that spawned at the top had a ranged attack, like the drill or penguin, getting past it was almost impossible because you couldn't see it until the screen scrolled up and you were already in its line of fire.
Speaking of, the wall jump worked fine, and was fun even, but telling the player they can do it directly would be a big help. The only reason I figured it out was because I knew this was a Kirby "clone" so when I was at the spot where you have to do the first wall jump in the castle, I tried jumping again in midair to float and I happened to be next to the wall. I actually managed to get "stuck" at the first boss because if you enter a door, any powerups on the ground disappear. I died to her, lost my last powerup, accidentally entered the door causing it to disappear, and then didn't realize I could wall jump back up and get a new ability, so I didn't have any way to damage her. That one's partially my fault obviously, but knowing I could wall jump sooner would have saved me the restart.
Finally, I don't know if this was intentional or not, but if you have a ranged attack, you can just snipe all the bosses from the doorways to their rooms before you're on their screen, and even leave their screens entirely to cheese them from a distance or avoid attacks. Depending on what you're going for, locking the player in to the boss's screen once the fight starts might be a good fix for that.
All that being said, I did have fun, and I know this was a game jam game, so you could only do so much with the time you had. What you did do was very impressive in terms of everything, art, music, and gameplay. If you ever decided to make a refined or expanded version of this, I'd absolutely play it.