Great concept and game! The spherical planet is a fun idea, but I think it would nice if there was another objective than just to survive.
What if you had keep the planet as small as possible by finding some kind of pickup in the map; While over time the planet grows; Making it harder for you to find these pickups, and of course when the planet gets too big; Your ship sinks (because the waves would realistically be too big)
Great game! I see potential here! :D