It's a really cool concept and I feel like it would be perfect for mobile. However, as it is right now, I think that there's a slight design flaw: yes, keeping more planets increases your score, but 1- score doesn't really do anything and 2- it's really easy to infinitely stay alive if you only keep one planet and just avoid the meteors. I would put like a timer that doesn't allow you to control a planet for too long, and maybe upgrades? like sun stages that can shoot more fireballs at once, or that can hold more planets at once, and you of course buy theese upgrades with the points you make (that can become currency)