Like a sushi roll, a puzzle may taste good, but it won't hold together if it's missing any pieces. Bite into brain toys with today's Groupon: for $19, you get a Mind Cube desk puzzle plus shipping from The Mind Cube (a $39 value).

Comprised of 216 rare earth magnets, The Mind Cube can be twisted and molded into seemingly endless sculptures and patterns to entertain and help ease overworked minds. Made up of 216 three-millimetre balls, buyers can accrue hours of amusement by molding the Mind Cube’s original shape—a six-sided block—into myriad geometric forms, puzzles, and desktop art. Each ball is its own magnet, allowing customers to use the pieces individually or in smaller conglomerations to post notes to a refrigerator or to play cupid with otherwise ambivalent robots.