Determining how hard to make something is always such a challenge. I am pretty consistently able to get to the last challenge, and sometimes beat it. I was out of time and couldn't play test that part any further, so ultimately I ended up making the speed of the black hole at the end only a tiny bit faster than the Earth part. I think due to it being bigger though, it is comparable to the playing field being smaller, which also increases difficulty, so in retrospect, maybe I should have left the speed the same as the Earth's.
It's kind of obscure, but in the first part, all of the points you score on yourself end up being the boss' HP at the end. Each time you hit him with the blackhole he loses hp, until he dies, and you win!
In the future it would be neat to code in a little bit of tracking that could relay back to me how far people get on their average play. I might have to set something up to use for that in the future.
Anyways, thanks for playing!