I don't understand the imperfect information thing. The whole game is assuming what the other player is attempting to do. Can't the other player not acting how you predicted be considered a bug? Or is this more formally defined than I'm aware of?
Information in this instance is the current (and past) state of the game. Poker is an imperfect information game because you can't see your opponents cards, and you can't see the cards in the deck. Chess is a perfect information game because you know where every piece is, nothing is hidden.