SPOILER

You unlock two new galaxies (a total of 10 levels) when you collect the Moon in all the first 40 levels

Groovy; that'll be good replay incentive, won't it?

I got the majority of them on my first run through, so not for me, unfortunately. Only one or two are actually tough, at least in the non-secret galaxies.

I just got the 50th moon and the last ending is so awesome! (Final 4 & 5 were really hard)

I got all the moons, nice game but Rotohex was better.

I'm damn late, but today I finally completed the game with all 50 crescent moons and saw/heard the crazy third ending.

9/10

However, does anybody know what the little silver spaceship does that randomly appears?

I still really need to download this awesome game. Especially since I absolutely love astronomy and cosmology.

Interesting anecdote about this game: One of the levels (I believe it was lvl 36?) can be completed without pressing a single button. You'll get sucked into a black hole twice, but after that it spits you out into a trajectory that results in you absorbing a bunch of planets and capturing the main planet. Pretty cool!

EDIT - The level in question is "Extreme 1" and you actually die four times by crashing into planets, not by getting sucked into the black hole.