at the University of Alberta and Carnegie Mellon University worked to develop poker playing programs utilizing techniques in game theory and artificial intelligence. In January 2015, the AAAS journal Science reported that the group at the University of Alberta had succeeded in coding a computer program called Cepheus that can learn from its playing experience to optimize its CFR algorithm and approach playing perfection when opposing strong players in the variant known as heads-up limit Texas Hold ’em, which involves only two players. Although it does not win every hand, it is unbeatable on average over a large number of hands. The program exhibits more variation in its tactics than professional players do, for instance bluffing with weak hands that professional players tend to fold. Public web access to observe and play against Cepheus is available. Starting hands Because only two cards are dealt to each player, it is easy to characterize all of the starting hands. There are (52 × 51)/2 = 1,326 distinct possible combinations of two cards from a standard 52-card deck. Because no suit is more powerful than another, many of these can be equated for the analysis of starting-hand strategy. For example, although and are distinct combinations of cards by rank and suit, they are of equal value as starting hands. Because of this equivalence, there are only 169 effectively different hole-card combinations. Thirteen of these are pairs, from deuces (twos) to aces. There are 78 ways to have two cards of different rank (12 possible hands containing one ace, 11 possible hands containing one king but no ace, 10 possible hands containing one queen but no ace or king, etc.). Both hole cards can be used in a flush if they are suited, but pairs are never suited, so there would be 13 possible pairs, 78 possible suited non-pairs, and 78 possible unsuited ("off-suit") non-pairs, for a total of 169 possible hands. Suited starting hands are stronger than their unsuited counterparts, although the magnitude of this strength advantage in different games is debated. Because of the limited number of starting hands, most strategy guides include a detailed discussion of each of them. This distinguishes hold 'em from other poker games where the number of starting card combinations forces strategy guides to group hands into broad categories. Another result of this small number is the proliferation of colloquial names for individual hands. Strategic differences in