Here are some games I found for you to play with and enjoy.
If you look around, there are several affiliated projects, many of which are open source.
Some may be of interest, particularly those of you wanting to design solar systems.
http://www.stefanom.org/spc/
http://www.stefanom.io/projects.html#systemic
http://save-point.herokuapp.com/dashboard/index.php
Janus.