These are the Professor Noggin' subjects dealing with geography in North America, as well as the world! The Countries of the World card games are one of the best selling Professor Noggin' games and you do not have to have series 1 in order to play series 2, but you can put them together to make a super deck!  The Fifty States card game is our only Special Edition double sized Professor Noggin' card game that we offer and it includes double the cards for..you guessed it, double the fun!