The colorful Hoberman Mini Sphere comes out of the box looking like a futuristic Christmas-tree ornament. It's a cross between a ball and a star, and measures 5.5 inches across. But pick it up by any one of its dozens of plastic points and this amazing little feat of engineering, or imagineering, expands neatly into a lattice-like globe that's 12 inches in diameter. The inventor calls it a trapezoidal icosatetrahedron. The structure is rigid enough to roll and throw, yet if touched in the right way, it will suddenly collapse again, curling in on itself like a defensive hedgehog. An enclosed pamphlet describes various tricks you can do--if you're prepared to practice. And it's so aesthetically pleasing that Mom or Dad may swipe it for a desk ornament.