Starcraft AI blog

Simplicity has been getting updates, and an update yesterday was apparently when it gained overlord drop skills. (There’s another update today.) It is the first zerg bot that I have seen use drops (well, in public at least). The drops look a bit stereotyped, with about 8 overlords loaded up in the main and sent (usually along the edge of the map) toward an enemy mineral line—it looks as though the drop happens when the overlords find targets to drop on. That makes Simplicity the first bot I have seen do mass drops, a unique skill.

I found 3 drop games on SSCAIT. Curiously, all 3 games are on Moon Glaive, although Simplicity does research drop on other maps. The less impressive games are Simplicity-Juno aka Yuanheng Zhu and Simplicity-NiteKat terran. Drops definitely did not change the outcome of those games. The best drop game is Simplicity-WillBot, in which WillBot randomed to terran.

The first drop started to load up at the zerg main just before 16:00 into the game—while a terran attack on the natural was underway, not the most auspicious time. Apparently Simplicity does not put much analysis into the drop decision. In the picture, the two players are roughly even (objectively, with no defilers in sight, the big terran army should win, but neither bot has the skills). The selected overlords are exactly those that are loading units. In the minimap, notice the long tail of terran units moving toward the zerg natural; the terran attack was kind of piecemeal.

Loading proceeded slowly, I guess since the ground units were distracted by the terran activity, and the overlords set out at about 16:40. The overlords proceeded counterclockwise around the edge of the map toward the terran main. Meanwhile, terran diverted to annihilate the zerg base at 9 o’clock before returning its attention to the zerg natural, and zerg units that were still on the ground bypassed the marines and tanks and headed for the terran natural to counter. Simplicity’s decision was good. Attacking the terran bases from both sides put WillBot into a difficult situation where it was tough to make the right choices.

The drop started to land at about 17:40. WillBot defended the ground maneuvers poorly; it left tanks forward to pressure the zerg, and lost them to zerglings, and sent marines back to defend, where they ran full tilt into burrowed lurkers. In the picture, notice that both sides have lost workers and WillBot has already fallen behind before the drop happened. The white dots in the terran natural are lurkers which are in range of the command center.

WillBot did finally clear the attack, but was far behind. Simplicity made 2 follow-up drops to finish off the terran main.

All in all, the mass drop skill could use improvement—but you could say that about almost any skill of any player. In Steamhammer, I have held off on zerg drop because I think it requires tactical analysis that the bot can’t do yet. In this game we see that mass drop can be a scary ability even with little tactical calculation behind it.