The latest Double Star release provides the full game experience: (1) training at the academy; (2) saving our planet from the alien invasion; (3) searching the galaxy for the enemy home world. Twenty levels are available for play. There are mysteries, challenges, and rewards along the way.
If you have not moved over to the new Double Star community, here is the link: https://plus.google.com/u/0/communities/113741436953313178716
More on the App
For more about the app, see the earlier blog article on Double Star.