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ZerGreenBot

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.

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Jay Scott on :

After more games, avoiding danger no longer looks to me like a weakness. Apparently ground forces count as part of the perimeter to skirt around, and ZerGreenBot seems mostly good at avoiding them. Even skillful defender Krasi0 was hard put to finish off the reavers (it lost a factory). But I saw ZerGreenBot fail against 1 mutalisk; it doesn’t seem to know about air dangers. Krasi0 should have made 1 wraith, a standard terran reaver defense. (Protoss should go with dragoons, though.)

imp on :

even if he knew about air dangers, from an AI perspective there is little he could have done (assuming the idea to lure the muta into the home base where dragoons are waiting is too far stretched).

So if there is nothing you can do about it, ignoring it might just be the right choice. Any reasoning would probably conclude that the shuttle is lost anyways, therefore you might just as well maximize damage.

There are several solutions to the (1-muta) problem of course. The simplest I can come up with is to start training a flying anti-air unit once the shuttle is attacked by a flying unit. Then let the anti-air unit fly the same path as the shuttle in attack-move mode during all subsequent drop missions.

Jay Scott on :

Or something like that! The shuttle can escape if it has speed (which ZerGreenBot does research before too long), but it will have trouble attacking. I expect that corsair-reaver would be a devastating strategy against zerg bots, but it’s famously difficult. Otherwise in PvZ it’s usual to keep reavers with the army or near cannons. Reavers are like high templar, powerful but vulnerable.

Jay Scott on :

Oh, and the reason I said that.... If the shuttle can’t get away with the reavers, then it should abandon the reavers where they have a chance to do damage. But ZerGreenBot let its shuttle die with the reavers inside. Its pick-up-put-down micro didn’t seem to include any consideration of whether the shuttle or the ground was the safer place. Which admittedly can be hard to figure out—take one step at a time!

imp on :

what's much easier to figure out and provides an extremely simple border case (I am a fan of simplicity, even though some of my posts may indicate the contrary):
just drop the reavers when the shuttle is about to die.

Jay Scott on :

Good idea, and probably close enough for now! “When the shuttle is about to die” still seems kind of tricky to me, but an approximation like “hit points just fell below 20” is simple.

Jay Scott on :

By the way, ZerGreenBot seems to have been updated at least twice since it was first posted two days ago, so the author must be working furiously! I haven’t compared closely, but the newest version seems to work its away around the perimeter faster, and to be more aggressive with its home units.

krasi0 on :

Seeing this new bot play is pleasant and refreshing and it seems like the author is hard at work so each new version gets significantly better.
Wrt my defense against Reaver drops, until now, I've never encountered a bot that does it so well, so it hadn't been a priority.
I think that for now my defense should do albeit suboptimally, but once ZerGreenBot starts biting really painfully, I might introduce more logic there. ^^

Jay Scott on :

Agreed on all points! After only a few days, ZerGreenBot no longer loses the shuttle with both reavers inside, and tries to coordinate an attack with its ground units as the shuttle moves in. It’s delightful, and if it keeps improving it will become a scary opponent. I expect to write about it more.

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