Like all multiplayer games based on Valve's Source Engine, Team Fortress 2 uses a client-server model. The client is the copy of the game running on a player's computer, while the server is the software which players connect to. There are currently several thousand Team Fortress 2 servers running worldwide. A server is responsible for many aspects of Team Fortress 2 gameplay. It responds to players' actions by updating their respective locations and states, e.g. firing a weapon, before determining an appropriate response, e.g. dealing damage to a target, and then broadcasting the results to the players, e.g. displaying a damage dealt value. The server also handles events that are not controlled by players, e.g. map time, Sentry Gun behavior, etc.