Normally when someone builds something in canvas, they set the canvas to clear between each frame. But that isn’t required. In fact, the default of canvas is to not clear. That’s what’s going on here, and the effect is bloody and awesome.
Canvas is Awesome
Roughly 60 lines of JavasScript to create 200 beautiful particles. The result is something more than a little hypnotic. I love restarting it over and over again to see what different colors I end up with.