Six sides. Six colors. Fifty-four squares. You know a Rubik's Cube when you see one.

Or do you? Like just about any product, the Rubik's Cube has seen its share of copycats since it first hit the market in 1974.

Now, it may get a lot harder to fend them off. On November 10, Seven Towns, the British toy company that owns Rubik's Cube, lost a trademark battle in Europe. Seven Towns has owned a trademark on the Rubik's Cube shape since 1999. The European Court of Justice just ruled it invalid.

The ruling came as a result of a lawsuit filed by German company Simba Toys back in 2006. Three-dimensional trademarks can cover iconic and unique shapes. Simba Toys argued that the shape of a Rubik's Cube is a result of its function and the toy should be covered only by a patent. The ECJ agreed, and its decision cannot be appealed.

The trademark loss leaves the door open for other companies to make similar cube-shape puzzles, so long as the inner technical elements aren't the same.

"This judgment sets a damaging precedent for companies wishing to innovate and create strong brands and distinctive marks within the EU," David Kremer, president of Rubik's Brand, told the Financial Times.

To find out more about what this might mean for the iconic toy, I spoke with Ian Scheffler, author of Cracking the Cube, who recently set out on a journey to become a speedcuber. He's since broken an elite barrier of cubing known as "sub-20," so named for the average time taken to solve the cube. (That's seconds, not minutes.)

The Rubik's Cube, Scheffler says, has sold more than 350 million units in its lifetime, making it one of the most popular toys ever made. Since the cube has always been distributed by private companies, exact sales numbers are hard to pin down. Sales dipped throughout the '80s and '90s, but a revival occurred in the early 2000s, which some attribute to the ability to watch strategy videos on sites like YouTube. With the renewed interest, annual worldwide sales reached 15 million in 2008. Scheffler estimates that number currently approaches 10 million units per year.

"It's perennial," Scheffler says, "like Scrabble or Monopoly--a continual feature of the toy market." And as new kids become old enough to play with them each year, millions more of potential first-time customers enter the market.

This is not to say that they're always picking up authentic Rubik's Cubes. There are plenty of knockoffs, Scheffler says, most of them originating in China, which he calls the "Wild West" for patents and trademarks, where laws are few and far between and rarely enforced.

Some of the Chinese products are specially designed speedcubes, intended for the community of elite players who sometimes make up to 14 moves per second. Those cubes might be designed so they can be rotated even if not at a perfect 90-degree angle, or with magnets that allow the individual cubes to lock in place more quickly. In a classic "if you can't beat 'em, join 'em" scenario, Rubik's Cube often licenses its name to speedcubing competitions, where competitors can use other companies' products. Scheffler compares it to athletic competitions that might be sponsored by Nike, where athletes are free to wear footwear made by any company they like.

Now, though, the Rubik brand might be at more risk. Some toy manufacturers were already producing similar rotating puzzles in other shapes, like spheres. It's hard to know exactly what kinds of competitors the lost trademark might inspire, but with no limitation on the cube shape, one would have to think European-based knockoffs are coming. They could spring up online, where most Chinese counterfeits make their sales, or make their way to smaller toy shops across Europe and the U.S.

Should that happen, the Rubik's Cube could lose some of its status as an iconic toy, which happened before, in the 1980s. "There were a lot of pirated cubes that flooded the market to capitalize on the craze," Scheffler says. "They were often of shoddy quality and impossible to twist. So in addition to being frustrated they couldn't solve it, people were disappointed they were using cubes that didn't work very well."

One thing Rubik's has going for it: The cubes are priced around $10, so buying a knockoff brand isn't going to save more than a few bucks, and possibly for an inferior product.

There's also the element of brand recognition. "The image of a twisty puzzle with colorful sides--no one will call that anything but a Rubik's Cube," Scheffler says. Even if the market share for Rubik's Cube does get sliced, it won't happen overnight.

So why is it even worth it for companies to bother making knockoffs?

"I've spent a lot of time thinking about what it is that makes Rubik's Cube such a successful product," Scheffler says. "I think the answer is that there isn't one single answer. Oftentimes if you can reduce a design object or a consumer product to just one feature, that feature is either quickly imitated and surpassed, or it just gets outmoded, or people get tired of it."

The Rubik's Cube, on the other hand, is both incredibly simple to understand and highly difficult to solve. When the toy was first introduced, it was deemed so challenging that its inventor, Hungarian-born Erno Rubik, often had to appear in front of wholesalers to prove the puzzle could be completed before the companies would agree to stock it. The cube can be solved using 43 quintillion (that's 43 billion billion) different moves. Scheffler compares it to a well-designed city transportation system: There are a seemingly endless number of ways to get to the same final destination.

It's that never-ending array of possible routes, and the allure of being part of the select people who can solve the puzzle, that keeps many people coming back.

And it's why one of the most iconic toys of all time should live on, even if its trademark does not.