http://universesandbox.com/
It has a trial and it's like 9 dollars on steam, pretty fun actually, of course it lacks a lot of things (Outerra to be specific) but i find it quite fun when I'm bored.
Not trying to advertise and i did make other topics and posts elsewhere in the forum, i just thought this game was proper to post since it reminds me so much of this engine (minus the actual worlds).
