This is cool, and I'm a sucker for gravity/space simulators (as my hours logged on Celestia would prove), but it should be noted that in terms of "galaxy" it's inaccurate. Specifically, this inaccuracy (the galaxy rotation problem) is the driving force behind the hypothesis of dark matter [0].

I don't mean to be pedantic or anything. I just think it's interesting.

[0] http://abyss.uoregon.edu/~js/cosmo/lectures/lec17.html