He led the team that wrote Chinook, the world's strongest American checkers player, after some relatively good results in writing computer chess programs.

Schaeffer is also a member of the research group that created Polaris, a program designed to play the Texas Hold'em variant of poker.

While Chinook became the world champion, it had never defeated the best checkers player of all time, Tinsley, who was significantly superior to even his closest peer.

The championship continued with Chinook defending its title against Don Lafferty when it lost one game, won one and drew 18.

More recently, the group has focused on the two-player (Heads-Up) variant, and has developed a series of programs that approximate Nash equilibrium strategies for the game.

In July 2007, Schaeffer announced a competition between the group's newest program, Polaris, and two human professionals, Phil Laak and Ali Eslami.