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Posts Tagged ‘design’

Flanking and Cover and Flee! Oh my!

Monday, June 13th, 2011

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.

Rubber-banding as a Design Requirement

Monday, May 31st, 2010

I’ve written about rubber-banding before over on Post-Play’em where I talked about my observations of how it is used in Mario Kart: Double Dash. Rubber-banding is hardly new. It is often a subtle mechanism designed to keep games interesting and competitive. It is especially prevalent in racing games.

For those that aren’t familiar, the concept is simple. If you are doing well, the competition starts doing well. If you are sucking badly, so do they. That way, you always have a race on your hands—regardless of whether you’re in first, the middle of the pack, or in back.

Sometimes, it can be more apparent than others. If competitors are teleporting to keep up, that’s a bit egregious. If you come to a dead stop in last place, and so do the other racers, that’s way too obvious. The interesting thing is that sometimes, it can be more than just about fairness and a running a good race. Sometimes it can be used because it is inherently tied to a design mechanic other than racing.

I saw this review on Thunderbolt of the new game Split/Second where it explains this phenomenon. The game is, on the surface, a racing game. However, in a mechanism borrowed from the aforementioned Mario Kart, the gameplay heavily revolves around “power plays“. These involve triggering things like exploding cars alongside the road, crumbling buildings, and helicopters dispensing explosives. You can even trigger massive changes for your foes like changing the route entirely. Needless to say, that has the effect of annoying the piss outta your opponents. The problem comes when those opponents are not human ones, but AI.

As the Thunderbolt reviewer puts it,

Split/Secondisn’t too difficult until some of the latter stages of the career, but unfair AI is a common problem throughout. It’s testament to the game’s focus on power plays that this unfair AI often occurs, since being in the lead isn’t a particularly fun experience when you can’t trigger the game’s main selling point. As a result, you’ll often find the following pack extremely close behind, often catching up six second gaps within two. Even when you know your car is much faster and you’re driving the race of your life, the AI finds a way to pass you with relative ease, performing impossibly good drifts and respawning from wrecks in the blink of an eye. Dropping from first place to fifth is such a common occurrence it would actually be quite comical if it weren’t for the frustration involved. That’s not to say Split/Second is a hard game – it’s usually pretty easy to wreck opponents with a decent power play, and you’ll normally be given ample opportunities to pass them – but the rubber band AI does cause some unwieldy races where the AI will pull ahead rather than keeping at a more realistic, surmountable distance.

As you can see above (emphasis mine), the rubber-banding is about more than keeping the pack close behind you if you are doing well. In order for the power plays to be relevant, you can’t be in the lead. You need to be behind them to use them. This is analogous to the “blue shell” in Mario Kart that would streak from wherever you were all the way up to the front of the pack and tumble the first-place kart. You simply can’t use the blue shell if you are in first place. In fact, the game won’t give you one if you are in first.

In Split/Second, the whole point of the game is blowing crap up and screwing with the other drivers. In fact, most of the fun of that is actually seeing it happen. While, in Mario Kart, you can use red or green shells, bananas, and fake blocks to mess with people behind you (and this is a perfectly normal tactic), the result of that isn’t the visually stunning and exciting experience that the power play in Split/Second is. Therefore, the designers of Split/Second had to make sure that you were able to use the power plays and see them in action.

In Split/Second the entire point of the rubber-banding is to make sure you aren’t in first—at least not for very long.

The difference between these two approaches is subtle. The rubber-banding in Mario Kart makes sure that, if you are in first, you can’t make a mistake without having people pass you. In Split/Second the entire point of the rubber-banding is to make sure you aren’t in first—at least not for very long.

You have to wonder how this mechanism would translate over to a shooter game, however. If rubber-banding in a shooter is to make sure you are challenged to a good fight… but one that in which you eventually triumph, a change to one where the AI is supposed to ensure that you don’t triumph would be a bit awkward. In fact, that would be negating the game’s purpose of having you see the rest of the content down the road (so to speak). AI in shooters is really cut from the same template of the rubber-banding in Mario Kart then. “Do well, and then lose.” It was just interesting to see a different take on this mechanism that generates a different outcome for the perfectly viable reason of making the game better.

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