Oof, honestly forgot that Block was a thing. I often played with it disabled because I was conflating side dashes with blocks. Adjusting the deadzones with my controller helped reduce misinputs, but I wonder if another/alternate input method would be good for that technique.
Ended up playing the rest to 100% completion on patch 1.1.
As you may have guessed, since I was willing to play to full completion: I liked this, a lot, and I'll be keeping a close eye on the full game. What you've put together for a demo has a boss roster that already puts a lot of full games, of any price range or studio, to shame - in quantity, and in quality.
I think the front half suffers from a certain lack of hitbox leniency and not having your tools yet, but when you get all the mobility upgrades and the range/damage buffs from Buddy 4 - that's when it all clicks, and things feel like they reach their peak. I would point out that bosses like Phan Phan are definitely more challenging in terms of moveset and patterns than Traitor Lord or Hive Knight (or really any non-Pantheon HK boss), and you have Monarch Wings and Shade Dash for those guys!
That being said, on top of the standouts I mentioned before, every boss from 21 onwards was fantastic. They were all just really fun, frenetic, and conceptually sound. Shoutouts to Daroach for being not too hard but really frantic and Dark Nebula for being totally redeemed.
28-30 are all particularly tough. I loved 28 and 30; I would echo CrankyTemplar's thoughts on the latter, as his video helped me find additional openings and get the Silver. 29 is fun too, but I would argue is actually the single most demanding fight in the game, even compared to the fights after. The 5-sword spin and the big petal pulse-in-and-out in phase 2, paired with the gaps in the bottom floor and lingering projectiles, is just a TON to juggle. If that's where you want him in the difficulty curve compared to the rest, I can't suggest you change much, though.
The bonus content behind the medals was the most fun I had with the game, which was the cherry on top to 100%ing.
Overall, this is great. I think design-wise these fights are very, very sound. I think it's a matter of shoring up the controls and hitboxes (coyote time, please!) and aligning the earlier bosses more with the upgrade curve at the start for the full release.
Impressive stuff.