Could one go to a computer software shop to fill a prescription for a product that can reduce the risk of developing or slow the progression of Alzheimer's disease in middle or old age? Apparently so, as many neurologists have suggested that playing Sudoku, the famous mathematical logic game, serves as "brain exercise" that can stave off dementias. Whether it is actually therapeutic or not, the game - whose grids appear in this newspaper and in thousands of others around the world - is a lot of fun for those who like to do mental workouts in their spare time. The worldwide craze, which has spawned strategy books, numerous Internet sites, clubs, videos, cell phone games, chat groups and even an Israeli set with plastic squares for playing on Shabbat without having to pencil in numbers, has now graduated to Israeli software. For just NIS 49, you have more than 1,000 arrays for filling in missing numbers, as well as hints and solutions when you've given up. The word sudoku (SUE-dough-coo, with the first syllable accented) means "numbers singly" in Japanese and is a registered trademark of a Japanese puzzle publisher. Although believed to have been born in the Far East, most experts trace its origins to Dell Magazine's Math Puzzles and Logic Problems workbook produced in the 1970s, which called the game Number Place. In 2004, a retired New Zealand-born, Hong Kong judge named Wayne Gould flew to London to persuade The Times to publish Sudoku puzzles. Gould did it at no charge, and the first puzzle was printed on November 12, 2004. It caught on like wildfire, spreading to newspapers from the US to Australia and Israel and becoming known as the "Rubik's cube of the 21st century" (remember those twistable cubes whose colors had to be shifted to difference surfaces?) and as the "fastest growing puzzle in the world." The best-known form consists of a 9 x 9 square grid divided into 3 x 3 sub-grids or regions, each containing all numbers from 1 through 9; 16 x 16 or even 25 x 25 grids are offered for the geniuses among us. There is no arithmetical relevance to the numbers; they could just as easily be types of fruits and vegetables or letters, and you don't have to have a large vocabulary as for crossword puzzles. Among the 81 squares, some numbers are already given as clues. Your goal is to fill in the remaining empty squares. But the rule is that each of the numbers can appear only once in each column, each row and each region. First check the column, row, and region each empty square is in, disqualify those numbers that appear as candidates for the empty cell and use the process of elimination to decide what number should appear in each. This inexpensive disk offers a short history of the game, instructions and tips in Hebrew only; none of these, unfortunately, can be printed out. If you know how to play Sudoku but don't speak Hebrew, you can manage very well nevertheless. The game offers the option of working against a clock and listening to soft background music. If ambience is important to you, choose any of six differently colored and patterned panels to serve as a frame for the grids. The game comes in easy, intermediate and (sometimes mind-boggling) difficult levels. Surprisingly, the level of difficulty does not depend on the number of numbers given at the outset. Techniques for solving the puzzle are scanning, marking up and analyzing (candidate elimination). Up to three numbers can temporarily be placed in each box to help you in the process of elimination. A light bulb icon can be clicked for hints. While strategies offered in the disk are minimal compared to the reams of material available in books or on Web sites, they are adequate for all but the most ardent players. So buy this game, and your neurons will be firing and your grey matter pulsing. Just be forewarned that Sudoku can be highly addictive.