Starcraft AI blog

After zerg Pineapple Cactus and terran Toothpick Cactus, protoss Prism Cactus is the latest in the cactus family. (Pineapple Cactus is the odd one out, since its name doesn’t match its race. Maybe the author will reimplement it as, say, Zig-zag Cactus?) Looking into the binaries, I get the impression that the same binary can play all 3 races (although the binaries are in fact not identical between Toothpick and Cactus, and Pineapple is a DLL.) For one thing, I see all 3 bot names in the binary, with the names of build orders for each race, and for another I see the name Rainbow Cactus, which sounds like it might be a random player. It’s weak evidence, though, especially since the protoss build order names don’t seem to correspond to how Prism Cactus actually plays.

Prism Cactus is performing a bit above average, similarly to Toothpick Cactus. The older Pineapple is a bit below average.

Carrying on the cactus tradition, Prism Cactus has a lot of nice skills, though it is not as polished as a top bot. It can use shuttle and reaver, and it gets psionic storm early and deploys it fairly well. It likes dark templar and it understands the enemy’s static detection range, so it doesn’t waste its DTs fighting next to a turret (curiously, the skill doesn’t seem to extend to shuttles versus static defense). It can make corsairs versus zerg. In the late game it adds carriers.

I have seen Prism Cactus play various build orders (which don’t correspond to the 3 protoss build order names I see in the binary). Its favorite is a tech build which branches: It either makes dark templar, or it researches dragoon range, or it gets zealot leg speed. It also knows a 14 nexus build, and a forge-expand build that I assume is for use against zerg and random opponents (the cannon timing is not rush-safe, though). I saw it open with 2 gates before core once, but that may be a reaction because its mining was disrupted. When playing the same opponent repeatedly, it switches build order after a loss, and I have seen it keep the same build after a win (there aren’t many games to go on), suggesting that it may use a bandit algorithm like many bots. Once the opening has played out, the rest of the game seems to follow a predictable path; it gets a shuttle and reavers, it gets high templar with storm, it expands. Apparently it doesn’t have any great strategic variety in the middle game, and it doesn’t research or upgrade much. But it can defeat weaker opponents by gradually out-expanding them.

Prism Cactus also has grave macro weaknesses. It gets supply blocked often. As it transitions out of the opening, it stays on 2 gateways too long, and is unable to spend all its minerals. It commonly goes over 1500 minerals before it expands and adds more gateways. Later in the game, with 2 bases and 5 or 6 gateways and gas-heavy production in its tech build, the mineral excess builds up again. Fixing the macro weaknesses would give the bot more punch. It would benefit from some combination of faster expansions, defensive cannons when useful, more gateways, fewer gas-intensive units, and masses of zealots (especially after zealot legs are researched).

Overall, an interesting bot with complex play. There is always more to do!