On the plane out to Chicago this winter the woman in the next seat pulled out a book of Sudoku number puzzles and went to work. I hope there was no smirk on my face, but I was thinking what a waste of time it must be to do the practically the same 1-9 puzzle over and over. Of course, that was before I ever tried to do one myself. What a difference a month makes. On my next plane trip, to Savannah, the woman next to me was doing the day’s newspaper Sudoko, but now I knew enough about these puzzles to recognize that she was basically guessing. (Even a little trial and error is a dead-end line of attack, not to mention that erasing newsprint is distressing.) By the time we arrived at our Elderhostel a few days later, I had gotten in the habit of trying to solve every Sudoku I encountered, and I made so bold as to offer some strategy tips to the woman next to me on the bus who was just learning about Sudoku. Now, most mornings I do at least one newspaper puzzle and one on the Internet. The best site I have found is http://sudoku.com.au/Default.aspx ; it offers new puzzles daily at four levels of difficulty and has several good options to suit a person’s favored strategies. Notice in the accompanying screen capture that all the possible numbers can be arrayed in given slot before the final numbers are figured out definitively; most online programs don’t have this capability and are more suited for printing out, solving, and then checking for accuracy. At this point, I approach each puzzle following a set sequence of solving strategies, although I’m still not too efficient (I may be ready to absorb a new principle soon, though). I can reliably solve puzzles designated Easy, Medium, and Hard, but I sometimes hit a wall on Tough or bail out because it’s not worth investing any more time. However, unlike with crossword puzzles, I’m pretty confident that every Sudoku is solvable and I can easily self-check my effort to feel a sense of closure…until tomorrow morning, that is.