Indeed, the comets are on the outer orbit. You probably didn't notice what they did because you were too good at the game. xD They're a second currency used to unlock better upgrades, but evidently you were cruising so well, you didn't need to know hahaha.
I think I'll add different difficulties next time. Half the comments are about how the difficult and balance is perfect, and the other half is about how it's too easy. Or maybe there's no way to please the masses ha.
I would've given your game a try, but then I saw that I'd already tried it, and that was a pleasant surprise. Thank you for trying mine out!