Each group spent about 15 minutes with me. When not with me, each group played chess games supervised by the Chess Program Director. I taught the Game Theory Challenge from pages 41-43 of my just-published book Thinking with Chess: Teaching Children Ages 5-14. For the Beginner and Experienced groups, I taught the rules of castling and we discussed why chess players castle. Then I called on students to answer whether or not one could castle in a given demonstration board position and, if so, what squares do the king and rook end up on. For the Advanced group, who were familiar with castling, I went straight to “why castle?” and the questions about specific demonstration board positions. After the lecture with questions, all groups had a chance to play the kingside and queenside versions of the Game Theory Challenge in pairs.