In Planet Armada you assume the role of a Radar Operator whose mission is to protect the planet from being destroyed.
The game has a very simple gameplay, just touch where you want to fire the missiles.
The game has a wave survival style, so the more time you play the more enemies you'll have to destroy. Also between waves you'll have to fight with giant bosses.
There's also missions to complete to unlock new content.
And to make things more interesting, the game has a shop where you can buy several powerups to help you during the fight.