Our approach, combining small amounts of “coaching” with self-play, allowed us to massively improve our agent between the Monday and Thursday of The International. On Monday evening, Pajkatt won using an unusual item build (buying an early magic wand). We added this item build to the training whitelist.

Around 1pm on Wednesday, we tested the latest bot. The bot would lose a bunch of health in the first wave. We thought perhaps we needed to roll back, but noticed further gameplay was amazing, and the first wave behavior was baiting the other bots to be aggressive towards it. Further self-play fixed the issue, as the bot learned to counter the baiting strategy. In the meanwhile, we stitched it together with Monday’s bot for the first wave only, and completed the process twenty minutes before Arteezy showed up at 4pm.

After the Arteezy matches, we updated the creep block model, which increased TrueSkill by one point. Further training before Sumail’s match on Thursday increased TrueSkill by two points. Sumail pointed out that the bot had learned to cast razes out of the enemy’s vision. This was due to a mechanic we hadn’t known about: abilities cast outside of the enemy’s vision prevent the enemy from gaining a wand charge.

Arteezy also played a match against our 7.5k semi-pro tester. Arteezy was winning the whole game, but our tester still managed to surprise him with a strategy he’d learned from the bot. Arteezy remarked afterwards that this was a strategy that Paparazi had used against him once and was not commonly practiced.