Attracting much attention from the exhibitgoers, was the "disappearing devil fan." A large replica is on display for people to try and figure out. Designed to rotate in a limited manner, the puzzle is created by fastening two concentric circles together. The idea is that when the puzzle is in its original position, you can count 13 devils. But when you rotate one of the circles just a little bit, one of the devils disappears.

The puzzle, of course, is to figure out how this happens.

The largest display in the exhibition is the collection of block puzzles, which are far from ordinary barrel puzzles.

Some of these block puzzles seem to be works of art as well as a challenge, made of cherry and rosewood, or combinations of fine woods varnished to a high lustre, so that they are almost too pretty to take apart.

Another "artistic" type of puzzle is the puzzle vessel. The idea is to try and find a way to drink the liquid from the vessel assigned to you without making a complete fool of yourself. Sounds simple, until you notice the holes in the sides of the cup near the lip of the vessel, making it impossible to drink in a normal manner.

Usually, the vessel has a secret siphon or straw in the handle (a remarkable feat of ceramic artisanship) with which the patron can imbibe.

But the most colorful type of puzzles (and the favorite of the viewers) are located in the "sequence puzzle" area. Such puzzles make you follow a precise set of rules to solve them.

One kind is the "shifting block" puzzle. One puzzle in the exhibition required the user to move a "car" through "traffic" or even use four "walls" to surround a "dinosaur."

Of course there are also examples of the 15-block puzzles which you now see sold in grocery stores as party favors. This kind of puzzle was actually invented in the 1890's and was used as a manufacturing and contest gimmick.

Four seperate displays are dedicated to three-dimensional geometric sequence puzzles. Perhaps the best-known and most obvious example of this kind is Erno Rubik's cube puzzle. That wonderful cuboid object, first marketed in the U.S. in the early 1980s, swept the globe, selling millions of copies in the process. It not only maddened the people who could not solve the easy-looking puzzle, but it spawned a generation of whiz-kids who could solve it in under a minute. Of course, some of these genuises wanted more. So manufacturers offered Cube spinoffs in odd shapes.

The exhibit has jazzed-up Cubes, with pictures of E.T., world flags, Prince Charles, and even Chex cereal on the sides instead of colors. But the most challenging puzzle in the six-sided genre seemed to be the five-by-five-by-five cube, one of only 20,000 specimens ever made.

For those who portend to have mathematical minds, this cube has about 1,213,783,704,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,00 0,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,00 0,000,000,000,000,000,000,000 combinations.

But only one solution.

There are also puzzles paying tribute to every regular polyhedron-pyramids, octahedrons, dodecahedrons, and those immortal icosahedrons, and all of them were in a blazing rainbow of colors.

Puzzles have been around for centuries, and they have obsessional properties, judging by the number of people participating in the hands-on exhibits on a recent day.

Some were busily trying to remove a wiffle ball from a knotted string, others building ducks from tangram "furniture," others diligently working on all 336 combinations of the six-piece burr puzzle, and others intricately involved with the implications of the geometric money puzzle.

"It's like any challenge: it's so easy to pick up [that] it's addicting," Gray says.