Tower defense

Tower defense (TD) is a subgenre of strategy video game where the goal is to defend a player’s territories or possessions by obstructing the enemy attackers, usually achieved by placing defensive structures on or along their path of attack. This typically means building a variety of different structures that serve to automatically block, impede, attack or destroy enemies. We see tower defense as a subgenre of real-time strategy video games, because of its real-time origins, though many modern tower defense games include aspects of turn-based strategy. Strategic choice and positioning of defensive elements is an essential strategy of the genre.