In an attempt to better explain what their game is actually about, UemeU's developers put together a new trailer. I think I understand now. And I'm amazed.
Give the trailer a watch here:
It's hard to believe, but all of that, everything, even the spaceship part, is from the same game. It's sandbox taken to its logical extreme: you really can do anything. I'm really excited (and somewhat scared; the internet is a strange place) to see what people will come up with when the full game hits. It should be quite the sight to behold.