So very pointless, yet unquestionably spectacular. The best kind of "art" performs no other function than to delight the viewer, and Japanese YouTube user Denha's complex marble machines do just that. But are marble machines art? You can call them that—or toys, scientific contraptions, engineering feats—but however you choose to label them, the best marble machines are complicated, skillfully crafted, and driven by the principles of potential energy, kinetic energy and gravity.