Starcraft AI blog

About detection as a counter—I didn’t find much to say. Get it when you need it, or that is, when you expect to need it (react to the future).

I do have a few general observations. Each race has invisible stuff that’s valuable even when the opponent can detect it. Invisibility is a force multiplier, but wraiths, spider mines, dark templar, and lurkers can remain strong when seen.

Also, detecting invisible stuff is not the only way to cope with it. The area spells nuke, storm, maelstrom, stasis, ensnare, and plague do not care whether units in their area of effect are detected. Maelstrom, stasis, ensnare and plague make cloaked units visible. Only nuke and storm affect underground units. Walling or physically blocking with units can keep dark templar from crossing a choke—they’ll have to fight their way through, gaining time to get detection. Terran spider mines can defend against dark templar without needing to detect them.

how to detect

Every race gets a static early detector (that also provides air defense) plus a flying detector. I assume that the combination static detector + air defense design is intended to balance wraith cloaking.

Because terran’s mobile detector is late, terrans get comsat for midgame detection. It’s part of the terran “low tech but adaptable” theme. Good opponents know how to exploit terran’s limited comsat energy: For example, dark templar can provoke scans at different places and times and eventually become able to get free hits. The more scans terran spends on cloaked units, the fewer are left to examine your base and your army composition and location.

The protoss twist is that observers both provide detection and are cloaked.

Zerg gets detection for free with overlords, so the main detection issue is usually whether and when to get overlord speed. For detection purposes, it’s a matter of weighing the safety of overlords and the ability to pre-position them where they may be needed. Whether and when you want to get drop also matters.

what needs detecting

Spider mines are so numerous that opponents often don’t try to detect them but force them or sacrifice units to clear them in a hurry.

Permanent arbiter cloaking more or less forces terran to get vessels and protoss to bring observers. Zerg usually has overlords all over anyway and doesn’t have much trouble.

Burrow traps are rare because they don’t often work, but we do see burrowed hydralisk traps sometimes versus corsair-reaver strategies. And burrowed zerglings for map vision and to delay expansions do appear in human play.

Apparently I have no deep insights into detection, but it was a request so I tried. Maybe it will be of use to bot authors who haven’t mastered the game yet.