Physicsy puzzles are a bit in vogue just now – the ones where you’ve given a bunch of bits and bobs and told to create a device to turn on a light or press a button. Here’s a demo of another, and it’s pretty cute. And best of all, it’s got Professor Heinz Wolff’s name on it. Remember him? Off of The Great Egg Race? It’s Professor Heinz Wolff’s Gravity.