Halo 2 is a first-person shooter developed by Bungie and the sequel to Halo: Combat Evolved. The campaign alternates between two playable characters: the human supersoldier Master Chief and the Covenant warrior known as the Arbiter. The game introduced online multiplayer via Xbox Live with an automated matchmaking system, dual-wielding of certain weapons, and vehicle hijacking. It supports both cooperative campaign and competitive multiplayer modes, and was the best-selling game on the original Xbox.