When covering the conversion of binary codes to gray codes and vice versa, textbooks on digital design almost invariably show implementations based on XOR gates, but the books' authors rarely explain ...

Using an old chessboard, eyelets, rings, weights, and string, [Alex] has designed a system that can show off all of the logic gates. This includes: NOT, BUFFER, NAND, AND, OR, NOR, XOR, XNOR.