Slotting is a technique which is used to confront the player with an overwhelming number of enemies and still give them a chance to win.
Instead of having all enemies attack at once, there is a limited number of "slots" of enemies which attack the player seriously, while the rest of the enemies keep their distance and just look threatening but do not do anything effective. In an FPS, for example, those enemies which don't have a "slot" might fire in the general direction of the player, but behave defensively while both their damage and aim is severely nerfed. But those enemies which got one of the limited "slots" will behave far more aggressively, charge the player and use far more effective attacks.
It is a very common technique which is surprisingly effective at allowing the player to fight large hordes of enemies while still not making single enemies so weak they don't pose a challenge at all.
It sounds strange, but it works surprisingly well because:
- In a stressfull situation, the player will concentrate their attention on immediate threats first (the slotted enemies which charge them) and not pay much attention to the behavior of minor threats (those mooks standing far away), so they will not even notice that the majority of the enemies behaves rather strange.
- While players are often very annoyed when games obviously cheat against them, they are often very forgiving to games cheating in their favor.
- Players like winning against seemingly impossible odds and are more likely to attribute their victory to their supposedly good skills instead of suspecting that they got help.
Remember: When designing AI for a single-player game, the goal of your AI is not to win. It is designed to lose, preferably in a way which makes the player feel good about themselves.