Resident Evil 4 is the sixth installment of the Resident Evil series praised as a revolution from the core games. It was the first title to implement a third-person view rather than the original fixed camera angles its predecessors had. Its mechanics have been completely revamped to incorporate fast-paced gunplay, quick controls and shoot-outs involving massive crowds of enemies in more open areas. The brand-new AI system and open environments allow enemies to work together to capture and corner Leon. Enemies are now humans, which allows them to climb up ladders, open doors, and use weapons throughout the game. Resident Evil 4 had one of the most tormented developments in any game, four proposed versions of the game were discarded by the developers before the finished product was released.