: Most stores sell a digital activation code (CD Key) that must be redeemed on Steam to download and play the game.

: Supports up to five players in online cooperative missions. System Requirements

: Missions earn you money to hire new team members or upgrade weapons. AI teammates can be commanded to perform specific tasks like covering locations or breaching doors.

: Other retailers providing Steam keys include Gamesplanet , Gamers247 , and Instant Gaming . CTU: Counter Terrorism Unit on Steam