Sentinel 3: Homeworld (Android) app for $1.25

Sentinel 3: Homeworld is the latest and biggest installment of the Sentinel sci-fi tower defense series. Your forces can finally take the fight to the alien homeworld. Launch a massive arsenal of weaponry to take care of enemy troops. But you can also get up close and personal on the battlefield with your special power armor that can level up and gain new abilities as you play. Execute devastating attacks and support your defenses!+