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Developing StarCraft 2 Build Orders With Genetic Algorithms
Jamie recommends a blog post from software engineer Louis Brandy explaining how using genetic algorithms to evaluate build orders in StarCraft 2 has led to some surprisingly powerful results. Quoting:
"One of the reasons build-order optimization is so important is that you can discover openings that 'hard-counter' other openings. If I can get an army of N size into your base when you do opening X, you will always lose. ... a genetic algorithm is a type of optimization algorithm that tries to find optimal solutions using a method analogous to biologic evolution (to be specific: descent with modification & natural selection). Put simply, you take a 'population' of initial build orders, evaluate them for fitness, and modify the population according to each element’s fitness. In other words, have the most successful reproduce. The program’s input is simply the desired game state. In practice, this means 'make N units' to determine some rush build order (but it also allows for other types of builds, like make N workers with some defensive structures and a small army)."
Who knows, with the help of this kind of technology, maybe I can play against Koreans without BEING HORRIBLY MURDERED! (Until they start doing it, at which point we're all proper-fucked.)
Friend: "The NIC is misconfigured..." Me: "No prob, I'll just telnet in and fix it." *Silence*
Traditional RTSes are all about memorizing the optimal build order (which apparently can now be calculated via an algorithm, removing the player almost entirely) and then being able to click really fast, and this is why I think it's a terrible genre. Hand-eye coordination should not even come into play in a game that calls itself a "strategy" game.
There are exceptions--those that aren't traditional RTSes, but are more real-time tactical games that focus on maneuver, flanking, suppression, and other actual military tactics instead of gathering resources and base-building.
The problem is that strategy is not inherently real-time and that too many people confuse tactics with strategy. The only games I've played that effectively combine the two are those that keep them completely separate, like the Total War series.
No one just plays the dang game anymore. Its all about winning via pre-built key sequences.
"Have you ever thought about just turning off the TV, sitting down with your kids, and hitting them?"
Exactly. An AI could win by exhibiting super-human micromanagement by engaging enemeies in several locations at once, diverting the attention of the human player. Unlike Chess, which is a turn-based game, Starcraft 2 is a real-time game. This gives people who can manage multiple conflicts at once while still pumping out units and maintaining their economy will prevail. An advanced AI would roflstomp a human. Blizzard's "Insane" AI for multiplayer still follows the rules of human skill. An AI bot designed to crush a human opponent would not limit itself like that.
TFA's method is designed to optimize rush builds, where the goal (ex. 7 roaches ASAP) is specified by the human. It wouldn't work at all for longer games where you have to respond to your opponent, since then your goals depend on what they do. At best, I'd say this method (1) provides strong but inconclusive support for the quality of various opening builds; (2) might find better opening builds that are not commonly known to humans. (2) seems much less likely than (1). I wonder if a brute-force all-branches approach is actually possible or even better than a genetic algorithm. For the first few minutes of SC(2) you don't have many options, so the branches wouldn't become horrifically numerous until several minutes in.
In any case, this method depends on humans to specify its goals and doesn't work in larger situations. I don't think there should be any concern about this type of AI beating "human ingenuity".
If I get SC2 I'll play the single player campaign only.
I'm really not interested in being pwned by someone who has a bunch of rush tactics memorised, let alone someone who's used genetic algorithms to optimise their deployment/build strategy.
Video games are designed to be fun
For whom? What do people consider fun? Do all people consider the same kinds of things fun?
I think the answer is no. In the case of Magic: The Gathering (the card game), Mark Rosewater (lead designer) thinks the answer is no---his three psychographic profiles Timmy, Johnny and Spike want different things. See http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtgcom/daily/mr11 and http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtgcom/daily/mr220a
I think these apply reasonably well to Starcraft (and RTSes in general). Let me describe them briefly, in terms of Starcraft 1:
Timmy wants to make a splash; he wants to build big units and cause a splash; he likes tanks, nukes and carriers.
Johnny likes quirky and underused combos; he plays the oddball strategy to see if it might just work---"I have to try statis-fielding my own units to trap the opponent on one side of the ramp", or "Can I reliably win using only melee attacks?"
(Johnny also likes to make quirky RPG builds, in the style of MongoJerry's pacifist Diablo II necromancer, see http://www.lurkerlounge.com/forums/thread-10277.html)
Spike plays to win, and will play whatever is effective. Do you 9-pool or overpool on a 128x128 map? Does the answer change on 128x192 maps? How do you react when the opponent goes for +1 attack _before_ +1 defense vs. after? How good are our relative zergling micro---do I win mirror battles?
These aren't hard-line categorizations; they're attributes you can have more or less of. (I'm a multiclass Johnny/Spike, FWIW.)
They will sacrifice [anything] if it will the game more fun. If that means the AI can be beaten, so be it.
For Spike, if you nerf the AI, you make the game less fun. If godlike micro lets Spike defeat human opponents, he wants an AI to help him hone his godlike micro skills (yes, they _will_ be godlike).
He will want an AI with human-like micro skills, so that he can simulate the real deal closely; he'll also want a different AI that will let him train specific skills---say, a macrobot AI vs. him self-imposing a macrobot playing style; or a custom scenario where you have to multi-task between microing a unit being chased and building your base to defend against the "5 minutes no rush" rush.
Thats what Spike wants. That's what's fun to him. Especially if he's Korean :-)
I don't think you get to tell him he's wrong (it's a chocolate vs. vanilla thing). I think you, if you're the right person in the right job, gets to decide that you want to make a game that appeals more to Timmy and Johnny. I don't think you get to decide that there are more Timmys and Johnnys in the world; that's an empirical question. You do get to comission a survey, though, and base your product development decisions on that survey.
(Based on recent developments in popular games, as I see them mostly from the outside, Timmy is the hot new market segment.)