The patroller is an enemy that moves within a pre-determined area. Once the player steps into the area, the patroller can either keep moving regardless of the player presence (such as the Goombas in Super Mario) or change its behavior, reacting to the player presence (for example, shooting or chasing the player, as with the guards in Metal Gear Solid).
It’s important to note that the whole point of the patroller is that it follows a movement pattern that the player can memorize in order to plan its actions.
