Diezemann got hooked on the puzzle when one of his sons gave him a book on it for Christmas a couple of years ago. “I just take to it when I have nothing else [to do] or I’m looking to kill some time,” Diezemann says—for example, when he’s waiting for his wife to finish up shopping. “I could spend a lot of time on it, but I don’t; it can become very addictive,” he adds. Though it may be  addictive, research has long pointed to the mental benefits of puzzles of this nature. “It’s a wonderful thing; it makes you think,” he says.

Method to the madness
In the first hour-and-a-half session of his spring course, Diezemann begins by explaining his method of solving a Sudoku puzzle, which he had written on the classroom’s white board. Though there are many ways to come to a solution, Diezemann suggests beginning with the top three boxes and looking for numbers that can be put in easily. He goes through the puzzle, looking at each column after having gone through the rows and boxes.

Once he puts a num ber in, he checks that the number cannot go anywhere else, and then he circles it. When there are two possible places for a number within one box, Diezemann suggests writing the number in pencil in the corner of both squares. In more difficult puzzles, there may be four possible numbers  or any one square; Diezemann will use the same method of writing each number with his pencil, so he can erase numbers as he eliminates them as options.

There’s always the temptation to speed up—and put numbers in without  checking them—but Diezemann warns against this: “There’s no substitute for step-by-step work.” Of course, there’s fun in it too.

As Diezemann puts the final number in the last empty square of the puzzle, the class erupts in cheers, having made it through three puzzles with the promise of more tomorrow.