Starcraft AI blog

Some successful bots play in a way that seems to me so unlike sound strategy that I feel morally obligated to beat them—or at least to try. Soundness must be upheld! I do it at the expense of teaching Steamhammer to play well in the general case, but it still feels worthwhile. It’s a quirk of mine, I guess.

As Steamhammer becomes more reactive I’ll remove some of these handmade counters, and when opening learning is in place I’ll drop all of them. But for now I think this is the way.

versus XIMP

The carriers must be crushed! For Steamhammer 0.2 I came up with a three hatch before pool build that puts a lot of hydralisks on the field, in the hope that they would tear down the cannon wall and win, or failing that, would hold off the carriers and bleed XIMP’s money away. I wrote up the first game. It didn’t quite work out; Steamhammer tore down the cannon wall, but with its other weaknesses did not have enough left over to win convincingly.

In later games, I found that Steamhammer 0.2 wins occasionally, but usually loses. It depends partly on the angle at which the hydras approach the cannons. Steamhammer doesn’t know the first thing about good formation, and when the hydras approach around a corner or otherwise in poor formation, they can’t take the cannons. The bot needs to know how to form up.

And it needs other improvements. It can eventually deal with either the cannons or the carriers, but when it tries to deal with both it loses. The tactical decision making is not there. Plus Steamhammer 0.2 has weak macro and doesn’t make as much stuff as it should.

Steamhammer 1.0 has adequate macro. It sometimes lets its minerals run up, but adds enough hatcheries to recover. Its hydra build is improved. The tactical decisions and formation are not improved, so I’m not sure how games will go.

For fun, I added a second three hatch before pool opening that goes mutas. We’ll see whether Steamhammer’s air power can prevail with adequate muta micro and disorganized scourge usage. XIMP goes corsair when it meets air, so I timed the build to produce the first 9 mutas simultaneously and hit hard before XIMP can react.

Versus XIMP, Steamhammer chooses hydra and muta each 50% of the time. Steamhammer already played 1 game versus XIMP with the air build, but it was on Benzene and Steamhammer’s third hatchery drone got lost due to the back door block—the same problem that Bereaver had against XIMP on Heartbreak Ridge, with the same sad result.

versus Iron

The vultures must be repelled! They don’t make sense as a mainstay against zerg. I tried an opening tailored and timed to beat the vultures without having to equal Iron’s superb micro. When I ran my specialized strat against an early December version of Iron, Steamhammer won 13-2. Iron is updated frequently, so as the tournament deadline approached I tested again against the 14 December version of Iron, and Steamhammer scored 8-7; that’s why I said that it had about equal chances. I messed up and my strat didn’t run during the tournament. But later I tried it against the tournament version of Iron, only a few days newer, and Iron won overwhelmingly! All respect to Igor Dimitrijevic, Iron improves at an incredible rate.

For Steamhammer 1.0 I put in a cheesy exploit strat, not a sound counter strategy. Against the tournament Iron it wins 13-2, losing only on 2-player maps. Iron improves so fast that I’m not sure it will work against the January Iron—and if it does, probably not for long! I have 2 different sound counter strategies in hand, but Steamhammer needs new skills before it will be able to pull them off. Eventually I hope to force Iron to play soundly, and then its amazing ability will be hard to touch.

versus Jakub Trancik

The cannon proxy scares me. If you see the cannons in time, they are no trouble. But what if you don’t see them? Steamhammer is none too sharp at scouting for surprises. In practice Steamhammer 0.2’s 9 pool is successful in stopping the cannons when no bug intervenes.

For Jakub Trancik I went with Steamhammer 1.0’s new “hidden base” skill in a 9 pool expo opening. This is Steamhammer’s only use of a hidden base in a far corner of the map. If the cannons are seen, lings will tear them down. If they are not seen, the zerg main will probably fall sooner or later, but the hidden base will live on. Steamhammer 1.0 is not fully robust, but it can often recover from losing its tech.

Steamhammer 1.0 also plays the 9 pool expo 20% of the time versus random opponents, because why not?

versus GarmBot

Against Aurelien Lermant’s GarmBot, Steamhammer plays its 13 pool opening—an opening that is specialized for play versus terran. By sheer coincidence it is also a strong counter to zerg GarmBot!