Creepy bug aliens are invading and are closing in on your base! Quickly, choose your fleet and position them to destroy the onslaught of bugs. Keep them from reaching your base and you’ll be in the clear…for now. Killing bugs earns you money to buy more ships for those tricky later waves. The fate of the galaxy depends on you!
Source
https://www.bubblebox.com/play/2318/galactic-defender.htm