With most information hidden, the game Stratego

Ataraxos, an AI developed by researchers from Carnegie Mellon, MIT, NYU, and Stanford, defeated Pim Niemeijer—arguably the best Stratego player—15 games to one with four draws. The system was trained on only 16 GPUs and a few thousand dollars. Stratego’s gameplay relies on 40 hidden-ranking pieces, with identities revealed only upon battle.