They walk down stairs, work out on treadmills, and freeze in mid-air, but have you ever wondered how a simple steel torsion spring became one of the world's best-selling toys? Join us as we take a look inside the curious history of the Slinky -- surely the world's most famous coiled-metal device. (OK, it's got some competition from the paper clip and the plumber's snake, but it's up there, right?)

A graphic designer by training, videographer 'Brusspup' got into the illusion business three years ago, bringing his technical know-how to bear on a lifelong fascination.

"I love the challenge of trying to come up with a new twist on each illusion," he told Yahoo! Games -- and his latest effort does just that by giving a classic perspective trick some new flavor.

Not unlike sidewalk art, the illusion is anamorphic -- it's drawn in a distorted way so that, from a specific perspective, it looks like a normal object.  But because this illusion has been captured on video, you can see the object take shape in real-time. It's pretty awesome when it all comes together:

"There is only one 'perfect'

No matter how exciting the prospect of a long, hot summer vacation might be, there comes a point where school suddenly doesn't look quite so bad. Right about mid-July, in fact. By now we're betting the kids are thoroughly fed up with TV, video games, books and outings, and have resorted to staring slack-jawed at the walls in boredom. And there's still over a month to go.

What's a parent to do but head to the toy store? Here are five new summer-suitable offerings that'll perk up even the most morose of vacation-weary youngsters.

(Credit: Getty Images)How many hot dogs can you scarf in one sitting? Four? Six? More? Sure, maybe, if you take your time.

So spare a thought for superhuman scoffer Joey Chestnut, who won last week's Nathan's Hot Dog Eating Contest by eating a staggering 68 hot dogs, buns and all, in just ten minutes. Talk about a gutsy performance.

But just how do pro eaters go about preparing their bodies for that sort of abuse? What separates a pig-out prince from a chowdown chump? Even if you're just thinking of entering the pie-eating contest at your local county fair this summer, consider gulping down these handy tips.

The perfect companion to a boring cross-country flight, Sudoku puzzles are now as ubiquitous as crosswords. If you love logic, you probably love a good Sudoku.

If you love sanity, however, you probably won't love Arto Inkala, the Finnish creator of what's being called the hardest Sudoku puzzle in the world.

It works just like any other Sudoku puzzle: fill the 9x9 grid with numbers so that each column, each row, and each of the nine smaller 3x3 squares contain all of the digits 1 through 9. But solving this particular brain-melter is significantly tougher than the cakewalk you'll find in an in-flight magazine.

Summer's finally here -- and it's already a hot one. Whether you're at the beach, by the pool, or just relaxing in the yard, there's nothing quite like a spontaneous water gun battle to liven up the afternoon and cool things down a bit.

These days, though, you won't have to worry about wearing out your trigger finger with a cheap, dime-store doohickey. Stock your armory with one or two of these high-powered aquatic weapons, and you're all but guaranteed to squirt victory right in the eye.

Stairs? Where this Slinky is going, we won't need stairs.

The science junkies at Veritasium decided to drop a Slinky and capture its descent on high-speed video, and the result is impossibly cool.

The Chinese used them for communication, taking measurements, and commanding troops. The Wright brothers used them to test their theories about flight. And Ben Franklin famously (and possibly apocryphally) flew them during a thunderstorm in an attempt to prove that lightning is really just a gigantic electrical spark.

But nowadays there are kites out there that would make old Ben drop his string, polish his glasses, and do history's biggest double-take. Next time you go fly a kite, take one of these along -- and the sky will  really be the limit.