Dota 2 is a 2013 multiplayer online battle arena video game and the stand-alone sequel to the Defense of the Ancients (DotA) Warcraft III: Reign of Chaos and Warcraft III: The Frozen Throne mod. Developed by Valve Corporation, Dota 2 was released as a free-to-play title for Microsoft Windows, OS X and Linux in July 2013, concluding a Windows-only public beta testing phase that began in 2011. The game is available exclusively through Valve's content-delivery platform, Steam. Dota 2 is played in discrete matches involving two five-player teams, each of which occupies a stronghold at a corner of the map. Each stronghold contains a building called the "Ancient", which the opposite team must destroy to win the match. Each player controls a "Hero" character and focuses on leveling up, collecting gold, acquiring items and fighting against the other team to achieve victory. Each match of Dota 2 takes place on a functionally symmetrical map that features the strongholds of two warring factions, the Radiant and the Dire. The Radiant is based at the southwest corner of the map, while the Dire is based at the northeast corner; the two sides are divided by a river that runs perpendicular to the central lane. These factions are defended by up to five players each, and are pitted against one another to compete as the defenders for their respective Ancient. In each stronghold is a critical structure called the "Ancient", a fountain that provide health and lesser structures. These bases are connected by three paths, referred to as "lanes" – two run parallel with the edges of the map, while one runs directly between the two bases. The lanes are guarded by defensive Towers, as well as autonomous characters called "creeps", which periodically spawn in groups and traverse the lanes, attacking enemies they encounter. Featured across the map are hostile characters referred to as "neutrals", which are not aligned to either faction and are primarily located in the forests. Located in a tarn on the northeast side of the river is a "boss" called "Roshan", who typically requires multiple team members to kill and drops powerful items..