I really liked the environment and character in this. It all felt very atmospheric, especially with the music.
I didn't end up managing to finish the game, because it felt like i kept going in circles. I'd gotten the glide ability, and then eventually managed to find the second boss, but didn't get anything for beating him, and then seemed to just go back to the second area's start again. I felt a distinct feeling of not knowing what I was trying to accomplish. I.e. I wasn't sure where I was trying to go or what I was trying to do. E.g. was that thing that teleports you to the second area (the dark cave place) the goal you want to get to each time? Or just a one time thing?
As some others have already mentioned, the lack of aerial control made platforming quite fiddly and difficult. I also had trouble with the acid(?) killing you instantly and chucking you back way to the beginning of the area. That felt quite harsh, and compounded the aerial control issue a bit.
But overall, I really enjoyed the experience. Nice job!