title for the genre was Westwood Studios's Dune II, which was followed by their seminal Command & Conquer games. Cavedog's Total Annihilation (1997), Blizzard's Warcraft (1994) series, StarCraft (1998) series, and Ensemble Studios' Age of Empires (1997) series are some of the most popular RTS games. MMORTS Massively multiplayer online real-time strategy games, also known as MMORTS, combine real-time strategy (RTS) with a persistent world. Players often assume the role of a general, king, or other type of figurehead leading an army into battle while maintaining the resources needed for such warfare. The titles are often based in a sci-fi or fantasy universe and are distinguished from single or small-scale multiplayer RTS games by the number of players and common use of a persistent world, generally hosted by the game's publisher, which continues to evolve even when the player is offline. Real-time tactics (RTT) Real-time tactics (abbreviated RTT and less commonly referred to as fixed-unit real-time strategy) is a subgenre of tactical wargames played in real-time simulating the considerations and circumstances of operational warfare and military tactics. It is also sometimes considered a subgenre of real-time strategy, and thus may in this context exist as an element of gameplay or as a basis for the whole game. It is differentiated from real-time strategy gameplay by the lack of resource micromanagement and base or unit building, as well as the greater importance of individual units and a focus on complex battlefield tactics. Example titles include Warhammer: Dark Omen, World In Conflict, the Close Combat series, and early tactical role-playing games such as Bokosuka Wars, and Silver Ghost. Tower defense Tower defense games have a very simple layout. Usually, computer-controlled monsters called creeps move along a set path, and the player must place, or "build" towers along this path to kill the creeps. In some games, towers are placed along a set path for creeps, while in others towers can interrupt creep movement and change their path. In most tower defense games different towers have different abilities such as poisoning enemies or slowing them down. The player is awarded money for killing creeps, and this money can be used to buy more towers, or buy upgrades for a tower such as increased power or range. A good example of a game of this genre is Clash Royale made by Finnish developers Supercell. Turn-based strategy (TBS) The term turn-based strategy (TBS) is usually