This game is simply awesome. Buy, Sell, Fight, Capture, and modify a large number of ships. You can steal modifications from other ships, and heavily modify yours. Additionally, the story line quests - that you don't actually have to follow - are a well written novel.
In combat you have several ways to command your fleet - or go it solo.
The graphics are acceptable, but nothing to brag about. It's the game play that is awesome.
Even better, the game is open source so you can create your own ships - even planets.
Oh, did I mention the game is free????!!!!