19. The Alien Operates On The 'Menace Gauge'
It's no secret that Alien: Isolation is a nerve-wracking and wholly terrifying player experience. A large part of this was down to the imposing and imminent presence of the titular alien that continuously hunts Amanda throughout her journey.
To maintain the fear factor throughout the course of the game, Creative Assembly had to get the Xenomorph's AI design right to keep the level of tension raised without the game ever reaching the point of being unfair to players. To do this, the team implemented the aptly named 'menace gauge'.
Similar to Left 4 Dead's 'stress meter', the menace gauge kept an eye on how much pressure was put on the player based on various factors including proximity to the creature, whether it was in line of sight, and how easily it could reach the player.
Whenever the menace level got too high, the system would then tell the alien to slink off elsewhere or retreat into the vents - allowing players to catch a much-needed breather before it inevitably came back for more.