Such gorgeous art! The subtle curving (vignetting?) at the corners of the screen looks really good too, I think - I imagine it’s implemented with a camera looking at the player object moving on a slightly curved track, like a… ring on a planet? Haha.
One thing I’d suggest is tweaking the camera so you’d be able to see a bit more below you - this got me a few times, like in the first level where the enemies follow you and you had to jump and land in a place below where you started it was difficult to see the obstacle.