Starcraft AI blog

New zerg bot Broken Horn is uploaded to BASIL only; it does not appear on SSCAIT. “Broken Horn” is the name of a zergling in Starcraft 2 lore. The name reflects the bot’s strategy. The bot was updated once after its first upload. I did not find signs of the bot on the wider internet, and I know nothing about the author (though I can make guesses). Without access to the binary, I can’t do my usual peek into it.

I watched a bunch of games. I can tell from details of its play that Broken Horn is a fork of a recent Steamhammer version—and there is only one recent release, the AIIDE tournament version 3.5.10. The long game Simon Prins - Broken Horn on Heartbreak Ridge is particularly clear in showing Broken Horn using Steamhammer skills later in the game.

Broken Horn always plays 3 hatch before pool. It varies the timing from 10 hatch 9 hatch 9 pool (fast for 3 hatch before pool) to 12 hatch 14 hatch 15 pool (extremely greedy; it immediately adds a 4th hatchery). I haven’t seen enough games to judge whether it varies the timing randomly, or based on learning, but I suspect it is random. In play, it uses the larva advantage it gained from the fast hatcheries to flood the opponent with masses of zerglings. It sticks with the ling flood for a long time, upgrading zergling speed but nothing else, then eventually (if the game continues) the opening line runs out and it falls back on Steamhammer’s strategy boss.

Is Broken Horn perhaps a Newbie Zerg production? See Newbie Zerg and links from there. It has that kind of feel. Matching characteristics are 1. Fork of a recent Steamhammer version. 2. A high-pressure cheese build. 3. It has only one basic build, but plays variations on it. 4. Steps to obfuscate the bot’s play and origin, in this case uploading to BASIL only.

The ling flood strategy often wins quickly. But an opponent that rushes will catch it unready, so it also often loses quickly. This is easy to see in the BASIL game length graph (bottom of the page), with a razor-sharp blue peak at 7 minutes and red in outlying areas. Terran BBS, or protoss 9-9 gates, or zerg 9 pool or faster should win with aggressive play. The opponent can also defend safely and tech to air units or anything else that a low-tech zerg is unready for, but that is trickier. The ling flood is powerful and easy to underestimate, and its size and timing depend on Broken Horn’s variable build timing.

In any case, welcome! New bots bringing new challenges are always good.

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