Long before Google's AlphaGo best Lee SeDol at Go, and IBM's Deep Blue bested Gary Kasparov at chess, there was Chinook: a humble software program that set out to compete with the world's greatest checkers player. Professor Jonathan Schaeffer wrote Chinook in an attempt to use machine learning to outsmart the unbeatable checkers master, Marion Tinsley. But Schaeffer couldn't have imagined how his relationship with Tinsley would affect his program, and how the drama of their matches would change the world of artificial intelligence.