Counter-Strike (commonly abbreviated to CS) is a tactical first-person shooter video game which originated from a Half-Life modification by Minh "Gooseman" Le and Jess "Cliffe" Cliffe. The game has been expanded into a series since its original release, which currently includes Counter-Strike: Condition Zero, Counter-Strike: Source, Counter-Strike: Anthology and Counter-Strike on Xbox. Counter-Strike pits a team of counter-terrorists against a team of terrorists in a series of rounds. Each round is won by either completing the mission objective or eliminating the opposing force. The latest incarnation of the game, Counter-Strike: Source, is based on the Source engine developed for Half-Life 2.
The game is currently the most played Half-Life modification in terms of players, according to GameSpy.
Counter-Strike was developed first as a Half-Life modification, and therefore named "Half-Life: Counter-Strike". The original version was a 3rd-party Half-Life modification, but since then it has grown into a commercial mod and later advertised as a separate game in itself. It still uses and runs on the Half-Life game engine and is based on its unchanged structure.
Counter-Strike is a first-person shooter in which players join either the terrorist or counter-terrorist team (or become a spectator). Each team attempts to complete their mission objective and/or eliminate the opposing team. Each round starts with the two teams spawning simultaneously, usually at opposite ends of the map from each other.
A player can choose to play as one of eight different default character models (four for each side, although Counter-Strike: Condition Zero added two extra models, bringing the total to ten). Players are generally given a few seconds before the round begins (known as "freeze time") to prepare and buy equipment, during which they cannot attack or walk/move (a player can still take damage, having the player drop from a certain height during freeze time was the only way somebody could control the players starting "HP"). They can return to the buy area within a set amount of time to buy more equipment (some custom maps included neutral "buy zones" that could be used by both teams). Once the round has ended, surviving players retain their equipment for use in the next round; players who were killed begin the next round with the basic default starting equipment.
Standard monetary bonuses are awarded for winning a round, losing a round, killing an enemy, being the first to instruct a hostage to follow, rescuing a hostage or planting the bomb.
The scoreboard displays team scores in addition to statistics for each player: name, kills, deaths, and ping (in milliseconds). The scoreboard also indicates whether a player is dead, carrying the bomb (on bomb maps), or is the VIP (on assassination maps), although information on players on the opposing team is hidden from a player until his/her death, as this information can be important.
Killed players become "spectators" for the duration of the round; they cannot change their names until they spawn (come alive) again, text chat cannot be sent to or received from live players; and voice chat can only be received from live players and not sent to them (unless the cvar sv_alltalk is set to 1). Spectators are generally able to watch the rest of the round from multiple selectable views, although some servers disable some of these views to prevent dead players from relaying information about living players to their teammates through alternative media (most notably voice in the case of Internet cafes and Voice over IP programs such as TeamSpeak or Ventrilo). This form of cheating is known as "ghosting".