I really liked all the pixel art and the music, good job with that.
The gameplay was way to precise imo, maybe adding coyote jump and jump buffering would help a bit but the main problem was the level layouts.
At the start they were very easy, then they became confusing and frustrating. If the player can't make a particular jump the level designer sould make that clear from the start. Take the famous italian plumber as an example of good level design, or even SuperMeat Boy.