This is our new daily carry toy: the Invixiball, a featherlight, Grade 5 titanium 30mm bouncy ball. Developed by Aaron Chow at Vixiv in Ohio, it uses a network of rhombic holes in a hollow titanium sphere to create a sufficiently compliant skin that happily bounces off hard things with a pleasant “tink.” About 308 years ago, a guy named Abraham Sharp wrote a book titled “Geometry Imrpov’d” on the topic of, amongst other things, cool polyhedra. On Plate II at the end of this book, you will find a