As you get bigger, the early planets run slower and slower. I'm not sure why. Are you rendering blocks for outer space? Whatever it is, you need to fix it or the game eventually becomes unplayable.
Also, you need an upgrade to increase how much resources you get or something like that. The later planets you have to beat quite a few times to reach the next planet, and after several prestiges when the planet is tiny, you'll still need to beat it just as many times. And upgrading resource acquisition would mean you can skip through worlds faster at the beginning so you don't spend so long eating a tiny dot. Or maybe just make it so eventually you skip the starting planets. Maybe let you upgrade starting money or starting planet too.
Also, it's easy to end up with one pixel left and not see where it is. I'd make them colored more clearly, but also make it so you need islands of a certain size (based on how big you are) for them to count against you in completing the planet. At the beginning, you have to eat every pixel, but at the end, five pixels on their own shouldn't count. Either that or make the resources glow once there's only a little left or something.