Throughout the history of puzzles and games, many of the biggest successes have come as complete surprises, because they've broken all the "rules."
Parker Bros. famously turned down the rights to the game Monopoly in 1934, because it had "52 design errors." It was too complicated, they said, it had too many pieces, and it took too long to play. So the inventor, Charles B. Darrow, produced and sold 5,000 handmade copies of Monopoly, they quickly sold out, and--once Parker Bros. finally bought the rights--it became the biggest game hit of 1935.
Similarly, the "experts" initially pooh-poohed Scrabble, Trivial Pursuit, crossword puzzles, and many other game and puzzle successes over the years.
Hardly anyone thought sudoku would be popular when it was introduced in Britain in late 2004 and the U.S. in 2005. The public was not interested in number puzzles, according to conventional wisdom. Yet we all know what happened. In less than a year, sudoku has become one of the most popular puzzles in history. Virtually every newspaper has made room for a daily sudoku, sudoku books have been bestsellers for six straight months, and sudoku tournaments have been held across the country and around the world. The Language Report named "sudoku" the Word of the Year for 2005.
The craze goes on and, to everyone's surprise, shows little sign of abating.
What's So Great About Sudoku?
The appeal of sudoku comes partly from the simplicity of the rules, which can be stated in a single sentence, and the compactness of the grid, just 9 x 9 squares--combined with some unexpectedly subtle logic. Even longtime enthusiasts may not understand all the techniques needed to work it. Sudoku packs a lot of punch for so small a feature.
Sudoku is a flexible puzzle. It can be easy, medium, or hard, which you can select according to your skills and mood. And the amount of time needed to solve one--generally between 10 and 30 minutes, for most people for most puzzles--is about perfect in order to feed a daily addiction. If sudoku took less time, it wouldn't pose enough challenge, and if it took more, you might lose interest or simply not be able to fit sudoku into your schedule.
Like crosswords, sudoku puzzles have blank squares that are inviting to fill in. It's said nature abhors a vacuum. We as human beings seem to have a natural compulsion to fill up empty spaces. A sudoku addict has difficulty turning a page that has empty puzzle squares begging to be completed.
Sudoku also provides an appealing rhythm of solving. Generally the first few numbers are easy to enter. Then, in the harder examples at least, you can get stymied and maybe a bit frustrated. Once you make the critical breakthrough (or breakthroughs), though, the final numbers can come quickly, giving you a rush and a heady sense of achievement--often tempting you to start another sudoku immediately. Hence the addictiveness of sudoku, which is the "crack cocaine" of puzzles.
On the following pages are 100 brand-spanking-new sudoku puzzles rated easy (#1-#90) and moderate (#91-#100). Every one has been checked, rechecked, and then re-rechecked to ensure that it has a unique solution, and that it can be solved using step-by-step logic. You never have to guess here.
As usual, all the puzzles in this book were created by my colleague Peter Ritmeester and the staff of PZZL.com.
Try them. And as one correspondent wrote me recently, you, too, will go "sudoku kuku."
Copyright © 2006 by Will Shortz Will Shortz has been crossword editor of The New York Times since 1993. He is also the puzzlemaster on NPR's Weekend Edition Sunday and the founder and director of the annual American Crossword Puzzle Tournament.