The marines in Half-Life used the “Kung-Fu” style of fighting, meaning that regardless of the number of marines that the player is fighting, only two are actually allowed to shoot at the player at any given time. No actual communication exists between the marines. Instead, each squad of marines is given two attack slots; if a marine wants to attack and both slots are filled, he finds something else to do (such as reloading his weapon or moving to a new attack position). When one of the attacking marines runs out of ammo, he releases the attack slot and goes into his find-cover-and-reload behavior. Then, one of the non-attacking marines, finding an empty slot, grabs the attack slot and starts shooting at the player.
A simple rule was added that whenever an attack slot opens up and there is more than one marine present, the marine vacating the attack slot should yell “Cover Me!” Although there is no communication between the marines, the perceived effect is one of a marine asking for cover and another opening fire to cover him. In reality, an
attack slot opened up and was filled by another marine who knows nothing about the one reloading.
в игре нет никакого AI верхнего уровня, управляющего этими отрядами, то есть всё поведение проявляется стихийно