Physics games are like National Geographic maps. I could stare at them for hours and feel like I learned something even if I couldn't articulate what I had been doing all this time.
This is Ball Droppings, which, despite its unfortunate name, is a good way to kill time before dinner if you're bored with surfing the web and don't feel like firing up your console for just 20 minutes. The premise - balls drop from a point on the screen, and you create boundaries off which they rebound. When they do, depending on the ball's speed, it creates a tone. It's an experimental game/application for Google's chrome browser but it works in most anything.
You can mess with the gravity and the drop rate to create some spooky-sounding tone patterns. Once I replicate the Close Encounters of the Third Kind signal, I'll move on to something else.