Starcraft AI blog

Monster’s elo is settling close to 2900, making it the top zerg with a margin. It has been updated at least once. One of the changes was to place outward-facing sunkens in a neat line, rather than a somewhat ragged formation, a clear improvement. I expect some authors will be thinking about how to beat Monster in the upcoming annual SSCAIT tournament, so here are a few thoughts. Though Monster’s author could read this too and make changes....

Monster does not want its sunkens to be broken, and often builds too many too early near the start of the game. That delays its economic growth. You can take advantage by delaying your own expansion a little to look threatening, and perhaps by killing Monster’s scout drone quickly. If Monster makes 2 or 3 sunkens in response to only a few units of yours, you are ahead. Don’t try for a bust at any early timing (even Stardust has to build up forces first). If you do make a lot of units early, you can try to contain Monster, to prevent it from expanding until you can get ahead, as in PurpleWave-Monster on La Mancha (an exciting game; the plan barely worked).

If you can run by the sunkens in the natural and get into Monster’s main, do it. Sometimes Monster walls tightly enough that it’s impossible, though. If you get in, Monster will run drones from its main to its natural, so you won’t kill many, but that is OK. There’s no need to destroy anything to get ahead. Stay alive in the main as long as possible to prevent drones from returning. Monster will be mining only one geyser and fewer than half as many mineral patches, and its economy will fall behind with every second. If mutalisks come out, they will come on half as strong at first, and they will need to clear Monster’s main before they head across the map to attack, so you have more time to prepare.

Against protoss, Monster most often plays with hydralisks, but may switch to mutalisks if you skimp too much on air defense. Corsairs are good for air defense, but I have yet to see a protoss bot which understands how to get the most value out of them. Monster is skilled with scourge, so you have to be careful with corsairs. You can see the general idea in pro games: As long as zerg has no spire, corsairs can scout and can clear overlords away. When scourge appears, protoss makes a cannon at the main nexus (initially only one, maybe more later) for short-term air defense and parks corsairs there until there are enough corsairs that they can shoot down scourge before it strikes. That’s about 5 corsairs. +1 air attack helps. Keep the corsairs in a tight group and they can go out on the map again, vulnerable only to determined scourge attacks with spread scourge, and even then the corsairs can shoot down some of it, raising zerg’s gas cost. If zerg has a lot of scourge, put dragoons or archons in your army and keep corsairs nearby; when in danger, fly over your anti-air units.

Against protoss and zerg, Monster opens with safe overpool builds that are not easy to exploit. Against terran, Monster plays a greedy three-hatchery build that leaves openings. Terran can try a cheese rush, or can take advantage of the slow zerg start to go for heavy macro itself. Hao Pan and Krasi0 have both tried proxy barracks, with partial success. Monster does have cheese reactions and defends itself fairly well if it sees the rush coming, though even then it may fall behind and lose. See Hao Pan-Monster, bunker rush not scouted and Hao Pan-Monster, bunker rush scouted (the scout overlord saw the first marine). In the second game Monster skipped its natural hatchery (it will also cancel a natural already started), made the hatch in its main instead, and got a sunken for defense. If Monster breaks the bunker early (which it often does) it typically wins; if it stays contained too long it will lose.

If you as terran go the macro route, you need good timing. Monster plays spire with +1 (usually attack but I have seen carapace too; is that due to an update?), then a second spire and double upgrades from then on. Terran has longer ranged units and low mobility, so terran usually wants to build up before moving out, especially if playing mech. But ground units do not stack and air units do, so if you wait too long then the mutalisks will defeat goliaths—all mutas can fire at once to pick off an edge goliath while not all of its comrades can get into range. Here is Krasi0 fast expanding to outmacro Monster. I think that this one is more instructive, though: XiaoYi-Monster on Empire of the Sun shows good terran unit mix and timing to beat the mutas. Ecgberht has also defeated Monster with the same kind of plan using bio units.

As terran, you also need good defense to survive until it is time to move out. Bots usually space turrets apart to cover ground. Pros don’t position turrets that way against mutalisks: They build turrets in tight groups so that a muta flock killing one turret takes as much damage as possible from others. The turret groups are located to cover vital areas: The mineral lines and production buildings. All buildings need to be placed compactly so that they are easy to defend, and they have to leave movement corridors so that mobile anti-air units can move quickly to counter the mutas. It’s not easy. Defense against strong muta harass needs skills.

Valkyries are potentially a sound defense against the mutas, but bots as far as I have seen do not use valkyries well. The valks act independently rather than together and move carelessly away from air defense, and Monster’s aggressive scourge shoots down too many; I haven’t seen an exception yet. Also, apparently terran bots select a single mutalisk as their valk target (this is my interpretation from watching replays), and Monster instantly separates the targeted muta from the flock so that only it takes damage. I suggest keeping valks in range of anti-air (whether static or mobile) for safety from scourge and trying Valkyrie patrol micro to in effect attack a location rather than a unit while staying safe. If that works, it should force the whole flock to scatter, rather than only forcing a single muta to split off. But I haven’t seen it tried, so I’m not sure it will work.