As Call of Duty 4: Modern Warfare's single player campaign unfolds, the player is introduced to new gameplay at every turn – one moment you are fast-roping from your Black Hawk helicopter after storming into the war zone with an armada of choppers, the next you are a sniper, under concealment, in a Ghillie suit miles behind enemy lines, the next you are engaging hostiles from an AC-130 gunship thousands of feet above the battlefield.