Thank you for the feedback!
What would've helped you for it to be more intuitive?
Making multiple sprites per boss was tedious, yeah, but I really wanted them to feel dynamic in their movement, so what was necessary.
The theme is included as the base thought of the player's movement and in a more noticable way in boss attacks. Each boss has at least one attack that's based on spinning, but each boss also has a special ability/attack that's also based on spinning, like grabbing you, spinning and throwing you away or teleporting by spinning into a vortex for ecample. Maybe you didn't encounter this?