Dota 2 is the standalone sequel to the extremely popular action-RTS map/mod 'Defense of the Ancients' for Warcraft 3: The Frozen Throne. The game consists of session-based online multiplayer activity, with the primary objective of each match being for the teams to destroy their opposing team's fortified stronghold. Each player controls a player character called a "hero", who is given the responsibility of participating in team combat, which generally takes place along a series of lanes that connect their opposing bases, lined with defensive towers. The gameplay elements are largely incorporated from Defense of the Ancients, with the game's lead designer, IceFrog, being the longest-serving and current developer of the Warcraft III mod. The emphasis of the game design is to preserve all the gameplay elements of the original DotA in the transition to the Source engine, while adding in many features lacking in the original WC3 engine (such as: multiplayer matchmaking, server-hosted games, live spectating, reconnection support, widescreen resolutions, etc).