This was great! I'm at 14 or so medals thus far? I have at least Bronze and Silver on most bosses and am going for Gold on Bosses 2 and 5 still.
Two points of feedback:
Stars scattered after an attack lands feel really ambiguous as to when their hitbox is active. I would jump right up through them on Dark Matter Blade to hit him during the lightning attack, but some other stars it felt like if I touched them at all at any point in their lifespan it was a hit.
Would it be possible for the charge strike to stall your downwards air movement? It takes a few frames to come out, which makes it feel clunky to do something like hit Whispy Woods' face. If it froze your air position for a second you could so some really cool "jump, airdash in, and pop them with a charge attack" sort of comboes.