Damian Isla of Bungie spoke at the recent Develop conference in the UK. He covered a lot of the history of Halo and some of the design decisions that were made in the franchise. Here’s a story from Gamasutra that covers a lot of good stuff.
Specifically, there’s a couple of things I want to touch on.
Halo’s designers wanted the title’s gameplay to explore mankind’s “primal games” such as hide and seek, tag, and king of the hill, and the game’s encounters were created with them in mind.
“It’s evolution that taught us these primal games,” said Isla. “They’re the ones that are played with our reptilian brains. The idea was for the AI [to] play them back with you.”
That’s kind of interesting from a design standpoint. I guarantee that no one is sitting there thinking “hey, this is like King of the Hill” but they all recognize the concept on a subconcious level.
Isla pointed out that the importance of territory in Halo’s encounter design is closely connected to the recharging shield mechanic that has appeared since the original game.
“Part of that recipe demands that at some point you have a safe zone,” he explained. “In a sense we needed to make the AI territorial. Once you have this idea, you have to think about the problem of encounter progression as the player expands their safe zone. That itself is a pretty fun process. It gives the player a sense of progress, and is extremely plannable.
This makes a heckuva lot more sense than the “arena + safe corridor + arena…” model. What Halo did was break it up theoretically rather than physically (i.e. with walls). However, there still was the knowledge that the dudes – while still in their territory – were still going to try to take pot shots at you. You could take cover and they weren’t necessarily going to come get you, but it wasn’t completely safe.
Isla made special mention of AI misperception — “the most interesting form” of good AI mistakes. If the player moves stealthily, the AI will assume the player is still sitting where the AI last knew him to be.
“Each AI has an internal model of each target, and that model can be wrong,” Isla summarized. “This allows the AI to be surprised by you, and this is very fun.”
Amen, brother! This is something that I love seeing. I remember reading some of Damian’s papers in the AI Wisdom series on exactly this concept of unknown location and search. Good stuff, man!
Still, Isla stressed, enemies shouldn’t be dumb. “It’s more fun to kill an enemy that’s cunning, formidable, and tactical,” he said, pointing out that that goal is not just an AI problem but also related to convincing animation and game fiction.
Dude… have I told you I loved you? I’m so sick of the mantra of “AI shouldn’t be smart, it should be fun!” As if those two are mutually exclusive of each other.
“In Halo 2, if an AI tips over his vehicle, he walks off and forgets completely he was ever in one,” said Isla. “In Halo 3, if he tips it, he remains in its vicinity fighting until there is a point where he can right it again.”
According to Isla, the latter approach is “the way things should be going” — as he puts it, “behavior should be a very thin layer on top of a world of concepts.”
I would argue that behavior is more than a thin layer. Otherwise, I agree. Which really brings the concept of knowledge representation to the forefront. Not just world representation (e.g. geometry), but a general concept of how agents perceive and conceptualize things (i.e. psychology). Again, I’ve read some of Damian’s papers on the subject. To me, he is someone who “gets it”.