Wow there are so many levels!
Very polished and fun to play, I love how you introduce new mechanics little by little, and I'm impressed by how much content this game has, including a boss at the end.
Visuals are top notch. Gameplay is quite straightforward, yes, but it definitely gets the job done. The only minimal feedback I'd give is that the running button being the same as the picking up items button sometimes make you regrab items accidentally on your way out. Oh, and the movements of the boss perhaps should've been telegraphed a bit better.
This is one of my faves so far, it doesn't explore the theme wildly but it does an incredible job of creating a full-fledged and cohesive piece of art. Great job! It reminded me of old-school pc-engine platformers.