Flanking and Cover and Flee! Oh my!

I was browsing through my Google alerts for “Game AI” and this jumped out at me. It was a review of the upcoming Ghost Recon: Future Soldier on Digital Trends (who, TBH, I hadn’t heard of until this). The only bit about the AI that I saw was the following paragraph:

The cover system is similar to many other games, but you can’t use it for long. The environments are partly destructible, and hiding behind a concrete wall will only be a good idea for a few moments. The enemy AI will also do everything it can to flank you, and barring that, they will fall back to better cover.

There is a sort of meta-reason I find this exciting. First, from a gameplay standpoint, having enemies that use realistic tactics makes for a more immersive experience. Second, on the meta level is the fact that this breaks from a meme that has been plaguing the industry for a while now. Every time someone suggested that enemies could—and actually should—flank the player, there was a rousing chorus of “but our players don’t want to be flanked! It’s not fun!”

“but our players don’t want to be flanked!”

This mentality had developed a sort of institutional momentum that seemed unstoppable for a while. Individuals, when asked, thought it was a good idea. Players, when blogging, used it as an example of how the AI was stupid. However, there seemed to be a faceless, nebulous design authority that people cited… “it’s not how we are supposed to do it!”

What are we supposed to do?

One of the sillier arguments I heard against having the enemy flank the player and pop him in the head is that “it makes the player mad”. I’m not arguing against the notion that the player should be mad at this… I’m arguing against the premise that “making the player mad” is altogether unacceptable.

“…it makes the player mad.”

In my lecture at GDC Austin in 2009 (“Cover Me! Promoting MMO Player Interaction Through Advanced AI” (pdf 1.6MB), I pointed out that one of the reasons that people prefer to play online games against other people is because of the dynamic, fluid nature of the combat. There is a constant ebb and flow to the encounter with a relatively tight feedback loop. The enemy does something we don’t expect and we must react to it. We do something in response that they don’t expect and now they are reacting to us. There are choices in play at all times… not just yours, but the enemy’s as well. And yes, flanking is a part of it.

It builds tension in my body that is somewhat characteristic of combat.

In online games, if I get flanked by an enemy (and popped in the head), I get mad as well… and then I go back for more. The next time through, I am a little warier of the situation. I have learned from my prior mistake and am now more careful. It builds tension in my body that, while having never been in combat, I have to assume is something that is somewhat characteristic of it. Not knowing where the next enemy is coming from is a part of the experience. Why not embrace it?

Something to fall back on…

One would assume some level of self-preservation in the mind of the enemy…

The “fall-back” mechanic is something that is well-documented through Damián Isla’s lectures on Halo 3. It gives a more realistic measure of “we’re winning” than simply mowing through a field of endless enemies. Especially in human-on-human combat where one would assume some level of self-preservation in the mind of the enemy, having them fall back instead of dying mindlessly is a perfect balance between the two often contradictory goals of “survival” and “achieving the goal”. It is this balance that makes the enemy feel more “alive” and even “human”.

If enemies simply fight to the death, the implication is that “they wanted to die“.

Often, if enemies simply fight to the death, the implication is that “they wanted to die”. Beating them, at that point, is like winning against your dad when you were a kid. You just knew that he was letting you win. The victory didn’t feel as good for it. In fact, many of us probably whined to our fathers, “Dad! Stop letting me win! I wanna win for real!” Believe it or not, on a subconscious level, this is making the player “mad” as well.

They want to win but you are making them choose to live instead!

By given our enemies that small implication that they are trying to survive, the player is given the message that “you are powerful… they want to win but you are making them choose to live instead!”

Here’s hoping that we can actually move beyond this odd artificial limitation on our AI.

Tags: agent based AI, Damian Isla, design, fleeing, Ghost Recon, Halo, using cover