I was watching the "Devs Play" S01E05 where JP LeBreton sat down with John Romero and played through Doom, while Romero would explain some of the game/level design choices they made.

There are loads of great points that both of them juggle around, though, there is one that I cannot fully understand. Maybe that's my language barrier or something, but yeah - Unit slotting.

It's a short segment of the video, starting at 2m56s where Romero has a little laugh about slotting in modern games.

I cannot seem to grasp the concept of it. Is it that units are auto-swarming towards you and attack in somewhat of a queue? Or maybe it's that their attacks are synchronized as to not overwhelm you? Or... what the heck is slotting?

up vote 106 down vote accepted

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.

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    ...and now that you know, most FPS are ruined for you :) – Philipp Nov 27 '15 at 15:31
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    -1 for 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.; without any hard game design source (book, article etc.) that would state that as a fact, it's a highly opinionated/conditional/dubious statement, yet stated as a fact here (see chat discussion). Please either remove it, rephrase it, or support it with some hard data. – vaxquis Nov 28 '15 at 20:08
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    @vaxquis: I think we can let people add the occasional opinion to what is otherwise a well-written and informative answer. This isn't Wikipedia. – Dietrich Epp Nov 28 '15 at 23:51
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    "When designing AI for a single-player game, the goal of your AI is not to win" , I'd replace "AI" with "enemies" and you'd have less contentious statement (for most sane games, for normal game situations). Creating intentionally stupid AI is only one option to allow the player to win, and arguably non-ideal option at that (if player notices, it can break immersion). – hyde Nov 29 '15 at 21:23
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    Only single-player FPS will be ruined. Multi-player FPS have more unpredictable Mook. – Mast Nov 30 '15 at 9:40

It's, I guess, about how the enemies run toward the player. Slotting implies that, to let the player survive and give her a chance to continue surviving, enemies coordinate themselves to not attack at the same time. So EnemyA will attack and continue attacking while EnemyB will wait his turn.

John Romero, in this video, explains that to avoid slotting but keep giving a chance to the player, in Doom ennemies are just slow. It gives the player a chance to run, avoid, and organize her strategy.

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