Success of The game left 4 dead as a survival Horror game not from a grisly story. However, all of that comes from a system that allows the game to set their own event that occurs based on the condition of the players who are in there. so, the components made in the game versatility can simulate the stress level after a lot of tension in the game and give the event in accordance with the situation. The result is a tense game of survival.
all of that is the result of statistics gathered by Valve, the company that makes game development game left 4 dead, come from the tester during the development game.
According to Gabe Newell, Valve leaders, even though the company has the ability to simulate the players in a game, not mean that the human tester game so it will be replaced by artificial alias machine versatility. the existence of the human tester is the most important part to determine the emotional and psychological impact on the gamer who play their game.