The bot has actually never seen Destroyer's big drones during training even once, so I found it somewhat surprising that it even works as well as it does!
Completely agree that adding something like the "League" used by AlphaStar would be one of the top priorities if you wanted to push this project further. I don't think CodeCraft is sufficiently complex to really allow for several very distinct strategies in the same way as StarCraft II, but I would still expect training against a larger pool of more diverse agents to increase robustness quite a bit.
Thank you for the kind words! I am also quite excited about the new points in game design space that RL will unlock and am planning write another blogpost on that topic.
CodeCraft is a programming game which you can "play" by writing a Scala/Java program that controls the game units. It's not actively developed anymore but still functional: http://codecraftgame.org/