This looks awesome ! Loved the visual style & the music fit very nicely.
The parallax backgound looks soooo great <3
My only small feedback is that it could use more player feedback when you take damages against the boss (maybe a little screenshake, a cute "ouch" sound...)
Appart from that it's a really great work especially solo. Wish it would have been a bit longer I would have love to play more of it :)