Starcraft AI blog

Steamhammer has 2 favorite lurker dysfunctions. One of them is kind of interesting.

Its #1 favorite blunder happens versus protoss. Lurkers act somewhat independently of the squad they belong to, because their burrowing ability lets them be more aggressive. But they’re not clever about it; they don’t understand detection. When a lurker sees a photon cannon, it understands it as a high priority target, walks up to it, and burrows in range. Then the cannon kills it. Not very interesting. I haven’t thought of a way to fix it without adding or rewriting too much code, so I put it off. I’ll fix it when I work on micro, likely in the 1.5.x series while I’m doing mutalisk stuff.

The second favorite blunder is less common but more interesting. It usually comes up versus terran. Lurkers approach a ramp with a bunker on top. They can’t see uphill, but when they get in range the bunker starts firing, so the lurkers can see the bunker and they burrow and start shooting back. Then the bunker can no longer see the lurkers, so it stops firing. The lurkers no longer see their target, so they unburrow, becoming visible... and the cycle repeats. Terrans that know how to place a bunker on top of a ramp generally know how to repair it, so the bunker usually wins. If the overlord catches up to provide vision, the overlord flies into bunker range and holds position... and doesn’t provide vision for long. This game versus Ecgberht shows it happening twice, before another lurker attack finally breaks the ramp because there were enough zerglings.

To fix the overlord behavior, overlords have to worry about threats. That’s on my menu for soon-ish. I may fix the lurker misbehavior with a rule like “if you’re on low ground and the target is on high ground and you want to burrow, move to burrow on high ground if possible,” that is, on the ramp. Ideally, the combat simulator would be able to tell whether the lurker can burrow successfully. Eventually I want to teach Steamhammer how to reason about visibility, instead of following rules.