It's a lot like Battleships, but with a maze.
Basically you each hide a yellow person on one of the 36 orange squares in your respective grid, and then construct a 6x6 maze around them through which the other player has to blindly search. I say 'blindly', because your opponent cannot see your maze, and has to slowly construct their own copy of it as the game progresses. Like hide-and-seek, whichever one of you lasts the longest without being found wins.
Herschel and I played several games of this this evening, during which I found the best thing about it to be that it's a two-player game, and therefore we didn't have to include Elmo. (who would have been laughing all the way to the champion's podium)
This is the point in the post when I would normally include a link to where you can buy a copy for yourself, but I think it would be more in the spirit of the game to just let you find your own way there...