Galaxy Quest is a casual base building strategy game in which your goal is to take control of the galaxy by defeating all planets. To do this you will need to build colonies, harvest resources and construct space ships for battle against each planet in the galaxy.
Each planet will have its own resource limitations and ability to build ships so you will need to strategize and co-ordinate resources between planets to ensure you have what you need to progress through the galaxy with increasingly more difficult planets to defeat.