Call of Duty 4 has one of the best and most influential multiplayer modes in the history of shooters. But its perks and progression system - unlock new weapons and abilities by earning XP, Prestige, then start over once you hit the max level - also represents a dubious inflection point in the FPS genre. It’s not as if grind, and earning rewards for grind, were completely novel concepts in shooters in 2007. The original Doom has par completion times on each end-of-level screen, and, back in the game's heyday, if you played a mission over and over and over again, and got your record down, you could have earned a place on the Compet-n leaderboards. Practicing, perfecting, and speedrunning through levels in Goldeneye is how you unlock cheats. In dozens of abstract forms, the grind-and-reward dynamic is as old as videogames themselves. Continue reading Counter-Strike creator's new game is everything the FPS genre needs right now MORE FROM PCGAMESN: Best FPS games, Best multiplayer games, Best co-op games