Woah this is too great for a first godot project.
The graphics were great and the music changing a great detail, The fire theme is awesome, but It clashed a bit much against the ice them,
the world swapping idea is a bit burned, Ive seen it a lot, and doesn't go 100% with the theme, but with your great spritework its compensated.
I think you could have polished the controls a bit, i felt it a bit slidey but still really good and there's a bug when you get ice-locked you keep accelerating.