There is a long tradition of strategy or war games in which a player cannot see the opponent's field. In these game, like the classic game battleship, players plot their own army or soldier layout, hoping to keep pawns safe. Ideal produced a clever take on this concept in 1972 with Battleboard. Two players place four knights and one king pawn on their side of a "castle wall." But after a move, the opponent "fires a catapult," meaning places a plastic bellows contraption over a free hole on the board. Pushing down on the bellows causes a stream of air to pass under the wall and towards a specific spot on the opposing field. If the opponent has a knight or king there, it gets blown off the board. Clever design very likely led to a fun contest.