There are two principal reasons to continue to do research on games ... First, human fascination with game playing is long-standing and pervasive. Anthropologists have catalogued popular games in almost every culture....Games intrigue us because they address important cognitive functions....The second reason...is that some difficult games remain to be won, games that people play very well but computers do not. These games clarify what our current approach lacks. They set challenges for us to meet, and they promise ample rewards