Plot: Fieldrunners 2 is a tower defense video game, the sequel to Fieldrunners, developed by Subatomic Studios. It was released on July 19, 2012 as an iOS title, specifically designed for the iPhone and iPod Touch. It is the third release from developer Subatomic Studios. Wikipedia
Plot: Anomaly: Warzone Earth is a real-time strategy tower defense video game by 11 bit studios. The game was initially announced in late 2010, and released on April 8, 2011 for Windows and Mac OS X. Wikipedia