It was an interesting move. My friend Christopher Rose, 10, had placed his knight in a position that I hadn't even considered. The knight was threatening me from a spot two inches off the chessboard.
"Christopher," I said in a sportsmanlike tone, "your knight is off the board."
"I know," he said. "Checkmate."
"But what if I just do this?" I said, lifting my king and placing him down on the carpet by my foot.
"You can't do that," he said.
"Because he can only move one square at a time."
It was true my king had been more than one square away from the edge of the board, whereas Christopher's knight had been poised right on the border, in position to lunge. I conceded.
"Anyway, a horse could jump off the board. A king wouldn't," he added as we put the pieces into their little plastic storage bags. It was a natural conclusion to our game, and Christopher headed off to his bedroom, moving toward the staircase like a knight—one step over and two steps forward.