ScrumbleShip is the most accurate space combat simulation devised to date. Gather resources, construct a capital ship out of individual blocks, then pilot it with AI or human help against other players.
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Hah, maybe not so much from the average gamer's standpoint, but I know what you mean.
Here's the blog article on it:
Dynamic.scrumbleship.com
It's more than it looks like!
Cheers,
-Dirk
Just as expected - the most exciting developments in the game tend to be those that are mostly invisible in the game itself :D