Very fun! It took me just a few seconds to figure out that there are a limited number of jumps. At first I was trying to figure out why I kept dying, but then I noticed the little squares. Was it intentional to not explicitly tell the player? For me, it was easy to discern after dying a few times. But some players might not notice for a while.
Perhaps you can make the removal of health boxes more obvious, e.g. like a little explosion, so it catches the player's peripheral vision, and they draw the connection between landing on the ground and losing one HP. What about making the health boxes hearts, to associate them with the heart refills? Just some ideas.
I thought the introduction of the heart refills was well done. You mention "health" in the in-game text previously, and the heart icon is generally associated with health. So no additional onboarding text was required.
Not sure about the music style. It has a sort of wandering, pensive feel to it. The drone-like texture is hypnotic. But your game is much more exciting! Something more upbeat with a conventional rhythm would be nice.
EDIT: Beat all 20 levels! The gameplay had a good hook that kept me wanting to keep trying until I finished it. I think it was because the levels were designed in a way that informed me it they are reasonable and possible to clear. The delightful particle effects were a nice touch. Do you have plans to expand on this game further?