Call of Duty 4: Modern Warfare

The series left the Second World War for the present day, but the turning point was the design of the multiplayer mode. Before this, a match ended with the match: the score reset to zero, and the next game started from the same place. Here every game earns experience, experience adds up to ranks, and ranks unlock weapons, sights, attachments and perks. The player assembles a loadout in advance and goes into battle with it, so multiplayer gained a long line that continues from one evening to the next.

A second mechanic grew out of this: kill streaks without dying grant reconnaissance, an air strike and a helicopter, meaning skill is paid for with levers of influence over the course of the battle. On reaching the top rank, you can voluntarily reset your progress and unlock everything again, trading what you've accumulated for a badge. The campaign is built differently: health regenerates on its own, the episodes move the player between different people, and in one mission the player takes no part in the shooting at all and directs an aircraft's guns from above, looking through a black-and-white sight. After this, almost every multiplayer shooter took up ranks and unlockable equipment, including the ones that aren't about war.