This has the potential to be a really great game, however I think it lacks polish and a few design choices stand in the games way to be amazing.
The biggest problem in my opinion is the combat. I think that everything is too small. The enemies are too small, the projectiles you shoot are too small and in addition to that everything is very fast. There is also no reason why I would every want to do combat. It's not fun, you aren't rewarded for it and doing it will almost certainly make you loose a lot of health.
That wouldn't be a problem if the combat wasn't such a big part of the game. If it was mostly exploration and storytelling with a few combat encounters and bosses I think I would have enjoyed it a lot more.
I really like how smooth you managed to make the planet gravity effect. It feels intuitive and the rotating planets look fantastic. In general the artwork is great.
Sadly the level design is also an area where the game is lacking. I think that it is very samey all the time. There were no unique or memorable segments or platforming setups. It just seemed very random to me.
I hope you found my thoughts to be useful feedback. Keep it up.