When you said hardcore, you meant hardcore. Sadly didn't make it past level two, so sorry there's some super cool content in the second half of the game that I missed.
I think this game would've benefit a lot from more responsive platforming controls. Small tricks like coyote time (letting you jump slightly after leaving the ground), jump buffering (letting you jump when you land even if you press the button slightly before touching the ground), and adjustable jump height (letting you jump lower if you press the button for less time) go a long way toward making a platformer feel fun and fair.
Coyote time and jump buffering are especially important in a game like this, where rotating platforms make jumping a crapshoot. When you land on a slowly rotating platform and try to jump again, it's really easy for your input to get eaten because either (A) you pressed it a frame before hitting the platform or (B) the platform rotated down so you were put back in the air. Some of my deaths were definitely from poor timing, which is fair, but a lot of them were from my jump input vanishing with rotating platforms.
It might also have been helpful to mess around with collision to make behavior with the platforms more consistent. Instead of having those quickly rotating platforms collide with the player and do whatever (maybe you'll get pushed up, maybe you'll get pushed off, maybe you'll try to jump and it won't work, who knows?), you could turn their collision off during the rotation. It would have the same effect but make it more predictable for the player: if I land on the platform while it's spinning, I'll always fall through.
Platformer feel aside, I really liked the music tracks for the game! Again, didn't get to levels 3 and 4, but I really enjoyed the first two tracks. Only audio complaint is that the jump sound is really loud; it should be more on the quiet end imo. Also thought the player character was cute.
Perhaps sometime in the future I'll overcome my skill issue and get to the other levels, if only to hear the sick tunes.