The simplicity of the Rubik's Cube puzzle is what makes it so devilishly difficult to solve at times. It's just a bunch of colored squares, but getting them to group together can be a life's pursuit for many people. So who in their right mind thought that taking the Rubik's Cube formula and adding mathematical patterns of numbers into the mix was a good idea? Clearly someone with a deep love of mathematics, or a sincere hatred for humanity.

At first glance you might assume the rules of Sudoku might come into play here, but they don't. Solving the six sides of this puzzle cube instead requires you to group the numbers into well-known mathematical patterns or collectionsâ€”including a Fibonacci series, a prime number series, and even the digits of Pi.

In other words, unless you've memorized these numberical formations, solving this puzzle will be all but impossible for anyone other than practising mathematicians. But it's great news for anyone with a math professor on their holiday shopping list, and a $20 limit. [ThinkGeek]