I was quite enjoying this until I got into the area with the background that has the planet with the cloudy ring. I don't know if it's a skill issue, missing an upgrade that would help me get out, or missing an alternative exit. But the only way I see to get out is a very unforgiving jump across three fireballs, up through a tiny crack, and backward through the spike area that got me down in the first place - with no checkpoints.
Up until that... the jumps seem really delicate - trying to jump off the very edge of a platform seems doomed to fail more often than not, and precision platforming with no jump height control is very painful (but may be part of the intended challenge). But otherwise, pretty enjoyable.