Starcraft AI blog

Back in March, one of my early blog posts was about a game between Iron and Killerbot in which Iron successfully ran by Killerbot’s static defenses with vultures and SCVs and cleaned out the main. At the time Iron didn’t have the skills to seal the win, but it was a promising start.

Soon after, author Igor Dimitrijevic turned off the runby feature. I suppose his development strategy was to get the basics down before adding such a risky skill. But more recently the runby feature is back. I saw Iron do runbys in September already.

Here’s a game played today where Iron rolled Krasi0. Iron opened with two factories making vultures followed by a starport. Krasi0 made a barracks and then immediately expanded behind a bunker. With repair, the bunker can stop most early game harassment. It’s a good opening.

The moment that Iron gathered 3 vultures outside Krasio’s natural, it ran by the bunker and into the main, like so.

1 vulture was lost in the attempt. The other 2 stopped all mining in the main. Notice the kill count—that vulture got 8 SCVs and 1 newly-made Krasi0 vulture.

Meanwhile, wraiths from the starport flew over as they were made and also stopped mining in Krasio’s natural. Krasi0 specializes in defense, but could make only feeble attempts to ward off the attack.

Runbys still rule, especially if you have aggressive micro skills like Iron. Lessons for the defender!

1. If you see a runby coming at you, you may be able to pull workers to physically block the runby. Then your static defense will drive it off. It’s an advanced skill, though.
2. You can place buildings to restrict the path for the runby. Krasi0 could have landed its barracks and/or built a depot near the bunker. Stopping runbys is one of the ideas behind IceBot’s building placement. Killerbot also has anti-runby building placement, though it’s not enough in itself to stop a runby.
3. Krasi0 could have defended better after the runby. The SCVs were too fearful. Krasi0 needed to gather resources and produce defenders to defeat the few attacking units; it’s no use to retreat SCVs at the cost of resources needed to win. In recent years I notice that pros increasingly often leave workers at work when a base is under attack, instead of running them, and I assume that’s their reasoning.