Starcraft AI blog

I had been hoping that Zia would start to choose between its openings, and now that it has I want to see how it’s doing. So I watched a bunch of replays. It’s using strategy learning, though I can’t say in what form. I predicted that choosing between its strategies would be advantageous, and it’s true to an extent.

With more variety, Zia has become more entertaining to watch. I like it. Zia plays these openings that I’ve seen:

• 5 pool
• 9 pool
• 9 pool speed
• 12 hatchery

I didn’t catch it playing overpool or 12 pool, which you might expect to be common.

Zia’s opening chat message gives a hint about its opponent model. It says “Nice to meet you!” for new opponents and “Hi again!” for opponents it has met before. And it either predicts a “harsh game” or claims “I may overwhelm you.” I think it picks the second message when it believes it has found a strong counter strategy.

Against opponents with a single strategy which is directly countered by one of these openings, like ZZZKbot’s 4 pool (hard countered by 9 pool plus a sunken so that the trickle of attacking lings has no chance whatever), Zia seems to learn the counter and should then win every game. Zia even managed to find a strategy that gives it a chance against IceBot—Zia won a game which brought out weaknesses in both bots, weaknesses I didn’t realize IceBot suffered from.

And I see signs that Zia adapts after the opening. For example, I saw it add a spire when it needed scourge for air defense. I get the impression that it decides flexibly between hydralisks, mutalisks, and lurkers for the middle game—at least it’s not hardwired, maybe it’s random, I hope it’s learned. I have seen it play 12 hatch, 11 pool, 10 gas and also 12 hatch, 11 gas, 10 pool; I hope it’s foreseeing how much gas it will want to boot up its future unit mix.

Playing many openings does have a disadvantage: It’s harder to play all of them well. It’s not enough to know the build, you have to know how to play it, and it adds up to a lot of knowledge. The worst is Zia’s 9 pool speed opening, which it plays in a strange way as a late zergling all-in: It makes 100% zerglings until it attacks around supply 20-24; if it fails, Zia doesn’t have enough economy for the middle game. (I expect a 9 hatch build would strike harder if you want to play that way.)

Zia still plays poorly overall, if you ask me. It needs to brush up on skills like not sending drones through the enemy army. It needs better scouting (it doesn’t send out its initial overlord), better tactics (no, don’t run up the ramp to fight the bunker! Hit the SCVs in the expansion first!), better engagement skills (big groups of zerglings should surround before attacking), and better micro (in lings versus zealots, retreat a ling that will die in 1 more hit). And stuff. It’s a hard game.

Zia’s current description is “Implementing more strats . . .” I guess the author has the most fun with that, which is all that really matters, but it’s not the way to a winning bot. Breadth of skills, not depth of skills: You gain more by reducing your weaknesses than by increasing your strengths. Zia already has relative strength in strategy, and will improve most with other skills.

Hmm, I should write a post about The Winning Attitude for authors of game programs. Only for those who seek the winning attitude, of course; it’s optional.

Tomorrow: Novelty maps.