Defense Grid: The Awakening is a classic tower defense strategy game in which players must protect their base from hordes of invading aliens. There are ten different tower types for gamers to use, and each tower has its own special ability that can be upgraded twice. All 20 environments encourage forward thinking by featuring a different placement of roads, tower build locations, and open areas, and each of the 15 different alien species offers its own unique set of challenges. ~ Christopher Brown, All Game Guide