Starcraft AI blog

ZerGreenBot has been updated repeatedly, and now plays a richer game. I liked its PvZ best; it opens with a forge fast expand and follows up with corsairs, reavers, and zealots, a strategy that is somewhat similar to mainline human play.

Here are shots from a game on Benzene against Tscmoo zerg. ZerGreenBot opened pylon, forge, cannon, nexus, gateway, cannon. It looks to me like a sound wall-in in the correct place (a couple spots need blocking units to be tight). On maps that don’t allow a wall-in, like Destination, it necessarily builds something looser.

ZerGreenBot’s first tech choice at the next level was stargate, starting air attack +1 before the stargate finished warping. Normal would be ground attack +1, but its choice seemed justified because the corsairs killed overlords throughout the game despite determined resistance. ZerGreenBot still tries its reaver drops versus zerg, but overlord hunting has become its top skill.

Unfortunately ZerGreenBot’s ground units fought so poorly that their code must be buggy. Even the air units showed some stuck-in-a-loop behaviors. Tscmoo won a crushing ground victory in the center and easily took it home. If its author keeps up the good work, though, ZerGreenBot is a threat to reach the top ranks. It has reaver drop and overlord hunting skills beyond any other bot. I think it also has the best protoss wall.

Meanwhile, Bereaver is already a top bot. I watched it battle Tscmoo protoss on the 2-player map Destination. Bereaver made an ill-advised attack across the bridges into Tscmoo’s natural and lost too much army. Tscmoo should have consolidated its advantage by expanding and containing, but instead tried to cash it in immediately with its own attack across Bereaver’s bridges. It could have worked against a weaker bot, but Bereaver defended efficiently with cannons, a reaver, and a handful of troops. Tscmoo overpressed, fell behind, and lost. It was a decent win against a tough opponent.

Next: SSCAIT map comparisons.

A quick note: The current version of ZerGreenBot has given up on reaver drops (at least for now), but it does know how to bomb tanks with zealots. I think it’s the first bot with that skill.

The new protoss bot ZerGreenBot was uploaded at SSCAIT today. It describes itself as “terribad” and... I can’t disagree, but it’s fun. To defend its base it builds zealots and dragoons. These units only leave the base if they are lured out. To attack it sends a shuttle with 2 reavers. It seems to keep building shuttles and reavers from one robo, so whether the first lives or dies, more will fly out later to attack independently.

It never expands. It doesn’t scout until the shuttle flies around the map. If it happens to see the enemy natural first, it never seems to realize that the enemy must have a main too. The shuttle disregards danger. Sometimes it drops the reavers near their target, but on the wrong side of a cliff. In one game ZerGreenBot took a couple potshots at an unfinished spire, a good first target, but then moved on—and the attack was later cleared by the first mutalisk. And yet its manic shuttle-reaver micro is fun! The basic procedure seems to be drop, fire at whatever’s near, pick up, move a little around the outside of the base, drop, etc. It’s as if it were trying to duplicate the Berkeley Overmind’s “dismantle the enemy base from the outside in” tactics. When there are two shuttles, they do a wacky dance.

One thing the bot does right is that it keeps the shuttle always moving, so that it never has to accelerate from a stop. I take that as a sign that the author understands shuttle-reaver micro and merely hasn’t implemented much of it yet (because it is crazy hard).

In the games I’ve seen so far, opponents react poorly to the reaver drop. They don’t understand that the shuttle is a high priority target, and they don’t know how to escape or how to attack. Even with no other improvements, better shuttle-reaver control by itself might make ZerGreenBot a dangerous opponent for many bots, though probably not for the top tier. If the goal is to play strongly, I suggest this order of improvements: 1. Better choice of targets and drop locations. 2. Attention to avoiding danger. 3. Smarter scouting, so that the better choice of targets bites harder. And only then work on expanding and being more aggressive with the other units. Well, it’s only my first thought; I’m sure the author knows better than I do.

By the way, I think the name is a joke. “Zerg-reen” sounds like a zerg marine, everything that is not protoss.