Really nice! I loved the graphics and aesthetic. Controls felt pretty good and I liked the puzzle platform designs! The one-jump mechanic was really interesting! You definitely designed the levels well around that limitation.
I didn't quite finish the game but I think I got pretty far. The death stuck bug caught me a few times and I didn't want to restart again from the beginning (R button didn't work for me either).
I think my main feedback is around the first checkpoint, if you miss the first feather jump, you have a long path to backtrack and get back to the checkpoint.. but it's just faster to jump into the electricity and respawn. I think if this was the intended punishment, missing the jump should just drop you directly into electricity and respawn you.
I also got stuck on the first cannon part wayyy longer than I want to admit lol. You'll see me struggle in the video for a while :P
Really great job and I'd love to come back to play again with some of the soft-locking bugs fixed :)
I really liked the screen transition effect too!