Starcraft AI blog

Here’s a whacky shot from a game between terran Iron by Igor Dimitrijevic and zerg Killerbot by Marian Devecka. I caught this on the SSCAIT live stream yesterday (yesterday in my time zone, anyway).

Killerbot is the strongest bot in existence, if you ask me, but here it is in trouble. Killerbot expanded, placed 3 sunkens and a maze of buildings to deter any runby, and set about teching up. All as usual. Iron also did its usual thing, rushing with speed vultures and a seemingly excessive number of SCVs.

Killerbot is so cautious about runbys that its blocking buildings sometimes block its own lurkers in its base. Caution didn’t help this time. Iron’s vultures ran through the natural and brought SCVs with them into the main. You can see a couple of the SCVs in the screenshot; the vultures are still in the main but are out of view. Iron killed the drones, killed the one defending hydralisk, and set about slowly-slowly tearing down the buildings. Killerbot has sharp strategies but it has the same fragilities as other bots—it said “hmm, the main is underpopulated” and sent drones in from the natural one at a time to die until it had none left.

If Iron expanded now, it could eventually accumulate enough vultures to kill the sunkens and eliminate Killerbot. But I believe this version does not know how to expand and is afraid of static defense (I saw it lose a game against AIUR on points because it did not attack the single well-placed cannon defending all the buildings in the main but instead gradually lost its vultures). On the other side, the queens do not have broodling. Stalemate.

At this point the tournament system had some kind of problem and aborted the game. In the regame, there was no runby and Killerbot won easily. So I never found out who would have won on points.

Lessons!

1. Runbys rule. I think the feature was recently added to Iron, and I expect it to help a lot. I haven’t seen any other bot do a runby. Runbys are common in human games, so I think they’re vital.
2. Expanding is a robustness measure. Iron already builds extra command centers, all in the same base. I expect a future version will know how to expand.
3. If there are things you can’t attack, then there are games you can’t win. If you fear sunkens, or if you can’t find floating command centers in the corner, you didn’t finish the game under your own power.
4. It’s good to have a fallback strategy to break loose a stuck game. ZZZKBot eventually makes mutalisks. LetaBot used to go wraiths. Even Jakub Trancik’s mass cannon bot finally switches to zealots.

Update later the same day: Igor Dimitrijevic sent me more information. He says my guesses about Iron are correct. About the new runby feature, he writes “Up to 3 times, if some conditions are met (some sunken / bunker / cannon prevents my vultures from reaching the enemy main base), some vultures and/or SCVs (at least one vulture) are ordered to runby, which is something they would otherwise never do.” Later he turned the runby feature off, and I’m not sure when or if it will make a return.

Iron has been updated again and it has another new feature: It makes tanks. Tanks can easily siege down the static defenses that used to hold Iron at bay. Igor is confident that, when tanks and the ability to expand are tuned properly with everything else, Iron will rise near the top of the SSCAIT table. Hmm... maybe it will. I can’t judge. How will Iron fight flying units or cloaked units or tank pushes? Is the rush so strong that it will stop the opponent from getting that far?