Starcraft AI blog

A heuristic: If the enemy has one medic and some marines, target the medic first. Nobody will heal the medic, and the marines will be softer targets. If the enemy has more than one medic, target the marines. Medics have armor and more hit points, they are happy to heal each other and they do no damage. The heuristic is not always right, but it seems good most of the time.

Another heuristic: If you are tearing down a base and may be interrupted, then a building that the enemy has only 1 of is more important than otherwise. If you find 2 x gateway and 1 x nexus, it may be better to target the nexus. If you find 2 x nexus and 1 x gateway, maybe the gateway is a better target. It’s not as firm as the first heuristic, but it seems to point in the right direction.

A similar idea is taking out one pylon that powers more than one enemy building. These can all be seen as special cases of key point analysis, where you recognize key points that are especially valuable to take out—or, if they are yours, to protect. The general idea is to understand what depends on what. You want to destroy the enemy dependencies that are the most important and take the least effort: The one medic, the one gateway, the one pylon.

Well, I happened to think of the first 2 heuristics and realized that they were related. It’s probably not time to implement this kind of reasoning in bots; I think for now it is enough to implement a few special cases as heuristics. But someday bots will be strong and will get into late game situations where precise reasoning makes a big difference: When to use your last minerals to make a cannon and surround it with dark templar, when to hide a pylon on a cliff, when to shepherd your probes with an arbiter for long-distance mining—that way of protecting your key points.