Even experienced puzzlers have described the Quartet puzzle as "too hard" and "nearly impossible." But if you're looking for an enormous mental challenge that can fit in your pocket, this is the puzzle for you. No undue force is required to separate the four pieces, just a complex sequence of moves that mindless fidgeting will never unravel. The good news is, it's not quite as screamingly difficult to get the pieces apart as it is the get them back together. If you reach your wit's end, don't despair. We'll be happy to send you the solution diagrams if you ask nicely.

Designed by Mineyuki Uyematsu for Hanayama of Japan.