# How to Play Sudoku for Fun and Mental Alertness

Use a pencil and good eraser.
Fill in the easy ones first. Notice that the circled 8 can only go in that square.
These circled numbers were found almost at a glance. I enjoy the pattern of never two of the same number in a line or square.
Twins. These tiny 2s are notes to help me remember that the 2 will fall in one of these two squares.
Pairs. This note means that these two squares will be a 2 and a 9 or a 9 and a two.
When you sketch all possible answers into a single square it can get crowded but in time you'll erase the notes and fill in just one number.

Sudoku has lately become a popular solitary pastime and group internet sport. The simple puzzle has certainly captured me. For those who are not familiar with the game, Sudoku consists of a large square divided into 27 boxes, 9 by 9 small squares, or 3 by 3 small boxes to make up a medium sized box. This makes more sense when you look at the pictures. The object of the game is to place the numerals 1 through 9 in vertical lines, horizontal lines, and boxes, including every number once and no number more than once.

1) It’s not math. The numbers are only symbols. You could use 9 animals or 9 fruits, but then you would have to draw, say, a bear every time a bear belonged in a certain square. Numbers are easier. (I understand they make Sudoku games for kids with cards to use, bears and such printed.)

2) Although a Sudoku puzzle looks a little like a crossword puzzle, you don’t solve it in areas, attacking one corner at a time as you might a crossword puzzle. A number in a far corner can influence others at a distance. So even if you are working on the upper left corner, you have your eye on the clues elsewhere.

3) If you try to play Sudoku on the internet you are competing with the whole world, which may be fun for the geniuses but hard on the rest of us. I prefer to play alone with paper and pencil.

4) Get a number 2 pencil and a good eraser. You’ll want to jot possible numbers in some of the squares until it becomes clear which one fits. Then you’ll need to erase your notes.

Strategies. I’m sure many people have used these strategies, but since they are methods I’ve worked out for myself, I will give them as my own.

a) The easy ones. Scan the puzzle to see what numbers are given to start you off. Notice where you have numbers already in the puzzle that make only one conclusion possible for a given square. Catch as many of these easy fill-ins as you can before you go on to other strategies.

b) Twins. Next, you will notice that sometimes the correct answer comes down to only two possible squares in a single line or box. I call this twins and I like to pencil in some small numbers. See the twin 2s in the picture.

c) Pairs. Sometimes you can narrow the possible answers for each square down to just two numbers, which I call pairs. See the pair of 29s. Even though you still don’t know which will be the 2 and which will be the 9, you can now eliminate the 2 and the 9 from all other boxes in that square and line.

d) Triplets. You can pencil in all boxes in a row of three as in the row of 4s pictured. This way you know not to put a 4 in the boxes not in that row. (I was stretching a point here since there is a 4 opposite the middle box, so that box cannot be a 4. I often make mistakes and notice them later, good for a laugh.)

e) One box at a time. When all other strategies have been used and I still need answers I will take one box at a time and pencil in any number that could go there. Somewhere along the way I’ll find a box where only one number will fit. Only with the very hardest Sudoku has this strategy not produced consistent results. Sometimes I get stumped. But it’s fun to have my skills challenged.

Like crosswords, Sudoku keeps you mentally fit. It can make you chuckle—and chuckling, like laughter, promotes longevity. May you grow as old as you wish and stay as smart as you wish.