You went above and beyond, this is beatiful! The juice and game feel on top of amazing art is the reason that kept me playing. Simplistic and easy to understand too, which allowed me to focus on the visuals.
That said, if I were to give constructive criticism, I would say the game may be too simplistic and unchallenging, and doesn't achieve the flow. Sometimes that's the vibe itself in games, but there could be challenges like a harder boss, or "mini bosses" among small enemies just to bump the challenge. Maybe one other thing is that the theme doesn't perfectly match the gameplay, far from feeling like the boss visually and mechanics-wise, which is something similar to what I have too.
Also I realized there was no mention of this, but I killed the boss, and pressed the button and I was stuck with the UI. Maybe I missed something there, but anyways. This is one of the best games that nailed the polish and the scope. Best of luck.