A well-crafted platformer!
I adore the visual style and your approach to the theme. The only thing I wish there was more in this game is the juice. The art you have is very much open to juice, and you can change it in a few hours of work only! Since you are a fellow Godot Engine developer, I'd suggest you check the particle system and environment nodes for some great post-processing effects. You can also polish the character movement feel with a few lerp functions.
Apart from those, the game is great and the options you give the player to pass the levels are awesome. One of the greatest games I have played considering the submissions. Keep up the good work!
Excellent job!