Tower defense (TD) is a popular subgenre of real-time strategy games. The main goal in these games is to kill incoming enemy creeps and prevent them from reaching a certain spot on the map like the entrance to your base. To do this, build towers that will attack enemies. Each tower will have certain traits that make it better at defending against certain attacks. Place your towers effectively to use resources in the most efficient way to overcome the invading enemies.
Each enemy destroyed will give a certain reward usually in the form of currency. Also, towers will be limited in capability and price. The process of killing creeps is how towers can be upgraded to withstand stronger waves of enemies. The maps often look like a maze-like, along the edges of the path it is suitable to build the towers. In some tower defense games, the player must build a maze of towers to slow down the approaching enemies.
Initially, tower defense did not exist as a separate type of game. The arcade game Rampart (1990) is considered to be one of the earliest representatives of the genre. Later, tower defense started to become a separate genre thanks to such strategy games as Warcraft and Starcraft. These games led to a large number of tower defense maps that were created with a map editor. A distinctive tower defense game was Master of Defense (2005), which gained incredible popularity and received the award of strategy game of the year. Later, in 2007 a game titled Flash Element TD sparked the tower defense boom in the oughts of the early 21st century.
