Monday, July 21, 2008

Gaming The System

Typically, a game artificial intelligence developer views their job as creating an opponent that will entertain the player. There's nothing wrong with this view. After all, if the player isn't having fun, it doesn't matter what the AI does well. The most realistic play in the world doesn't mean a thing if the player doesn't enjoy playing against it. It's possible to make AI that plays like that, of course. If a human can play so well it frustrates their opponent, an AI can do that too. But is the problem the AI design or the game design? I'd argue the game design is at fault. In other words,

AI design is a counterpoint to game design.

Game design really has two parts to it: making the game fun and making the game challenging. Alternatively, you can think of this as making the game fun for the winners and making the game fun for the losers. If a game is too easy for you, then chances are your opponents are getting crushed and aren't having a good time. A good multiplayer game is one in which everyone enjoys it regardless of whether they win. And a good single player game is one where it's neither too hard nor to easy to win.

That means AI can be a valuable tool in the design feedback loop for a game. If the AI continually exploits a certain unsatisfying strategy, you can expect players will do the same, and the game should be changed. When the AI uses a variety of interesting strategies, that's a good sign your game design is solid.

In the design of BrainWorks, I came across a few instances of AI behavior that commented on the game design of Quake 3. For example, on any level with a reasonably accessible BFG, the bots will do everything in their power to grab and use the weapon. They might even camp BFG ammo just to make it harder for other people to use the gun. While it makes gameplay boring and predictable, they aren't necessarily doing the wrong thing. The AI determined that the BFG was 10 times better than the next best option and made it choices accordingly.

There's also the issue of the machinegun. You might notice that if there are a lot of players on a level, the bots will sometimes flat out skip weapon upgrades and just use the machinegun. This also isn't a mistake. When there are more players on the level, each player's life expectancy decreases. When the bot won't live that long anyway, there's no point in wasting time for a new weapon. The starting machinegun is only slightly worse damage and comes with a reasonable amount of ammunition.

In the case of the BFG, the weapon is obviously too powerful, but it's pretty clear that was the point. The machinegun is a different case though. Is it really too powerful or do players just start with too much ammo? Or maybe it's fine that this is a strategy when a level becomes overpopulated, and human players that waste too much time picking up weapons are just playing it the wrong way.

This is just opinion, but I believe the problem is the amount of damage the machinegun deals. The reason I think this is that there are actually has two damage values for machinegun bullets. Normally it's 7 damage per hit, but in teamplay mode it's only 5 damage. Apparently iD software determined that in a teamplayer game, the standard 7 damage was too much. And they're right, but the problem wasn't the weapon's use in team games. It's the weapon's initial power in games with lots of people, even large free-for-all games. What would be best is if the weapon just dealt 5 damage always. Then freshly respawned players had incentive to grab a new weapon as soon as possible. In game design, the simpler solution is usually the best choice.

On a related note, game design is also a hobby of mine. My wife and I have two upcoming board games that will hopefully be released end of this year or beginning of next. If people are interested in more columns explaining the thought process that goes into game design, I'm happy to write more on that subject. In my mind, designing a game is very similar to designing artificial intelligence.


BvG said...

Yay for more game design!

Jonathon said...

I like reading the game design posts as well.

I do take a little issue with the machine gun comment though. Wouldn't making it flat out 5 damage have a serious impact on smaller sized games (especially a competitive 1v1)?

In a 1v1 or other small match I'd think you'd run into problems where players who die would be unable to get a weapon quickly enough to be back on even footing. In more competitive matches (which are often smaller sized) I know it's rather common for professional players to know the weapon and spawn locations. If the machine gun was weaker and the professional player could get on top of their opponent after they died (but before they can nab a decent weapon) they'd be able to just run away with the match.

Anonymous said...

But jonathon, with fewer players there is more time to get a good weapon after respawning; no matter how well a strong opponent can patrol respawn and weapon locations, a significant amount of luck is needed to run into an outgunned victim.
In a decent map without unacceptable sniping and camping opportunities the "professional player" cannot expect to kill the weak players again before they get a good weapon; the positive feedback against respawning players is much weaker (they collect good weapons instead of stockpiling much less useful items, and they must move fast to get them without the luxury of hiding and stalking freely).

Ted Vessenes said...

Keep in mind that in typical settings include a really fast weapon respawn rate, 5 seconds I believe. And even a 1v1 level has at least 3 weapons available, so it's impossible to dominate all of them. The initial machinegun seems designed to give players a fighting chance until they get their hands on a real weapon.

Now that I think about it more, perhaps the best fix would be to make the weapon always deal 6 damage (instead of 7 normally and 5 in team games) and reduce the starting ammo from 40 to 25. That's still enough ammo to hold your own until you can get another weapon, and the 14% decrease in damage in incentive for that too.

Lowering the base ammo means that ignoring weapon pickups is only useful if you would die 40/25 times as fast. So you'd still do it with 15 players on a cramped level, but not in general. I think this hybrid solution would be the best.