The Heavy uses a large machine gun to provide brute force on the battlefield. For instance, a Doctor goes around healing his teammates so they can fight longer and harder, but has little combat prowess. Team Fortress 2 is the sequel to a Half-Life mod, and attempts to mix of the traditional system of multiplayer shooters by adding in classes and a huge variety of weapons with different behaviors. Though its audience is generally limited to PC gamers, its visual style is recognized by many, and its system of character roles and varied weapons has marked it as a very unique multiplayer experience. Team Fortress 2 has become something of a phenomenon in the video game world.