...there's nothing when you actually win in survival mode. My star got sucked into the middle but was bigger than any of the stars there, and grew larger than the screen so you couldn't see the edges and the whole area was yellow. After a few minutes, there's nothing left to do but click "give up".
I survived survival mode! Took about 2 1/2 hours and grew bigger than any of the orange planets...after absorbing everything on the screen, the only thing left to do is hit "give up" but that doesn't let you post a score. Other than that, good game!