This was fun to play! It took a little bit to get used to the controls (I kept switching between left shift and right shift, right shift + space + wasd ended up being what I settled on.) I got super stuck at 4-1 and had no idea what I was doing wrong. The mechanic the level was asking me to pull off didn't click for me until I watched some gameplay from your youtube video that showed the long jump leading to a super high jump. I saw that and immediately went "Ohhh that's possible?!". With that knowledge I did pretty good until 5-2. I just couldn't seem to get enough jump height from the second platform, it took me a ton of tries... I kept thinking that the speed of the platform rising would transfer into my jump speed, but it seems like I actually jumped higher when it stopped moving which kind of confused me.
Not finished with this yet, but I'm currently at 6-1. The game's got its hooks in me, definitely a good thing! Hoping I can finish it sometime. The art style is simple, but nicely polished. Music and sound effects are great as well. I know nothing about music theory really, but I did happen to know some of the names of the levels and thought that was a really cool idea for level names. Very cool game overall, great work!