I had some issues getting the controls right as walking around the planet would kinda switch the movement direction and figuring out how gravity would affect my projectile's path was kinda frustrating until I somehow got it. Maybe consider adding another layer of tutorial to it.
Anyway, I really liked the art, the sfx and music was great. The overall concept, given some friends to play with, will likely be an awesome and fun experience.
Keep up the great work :)