The good old animated drawing where points move in a direction and hitting a border change x or y direction to bounce against it is basically what I have created here. I use requestAnimationFrame to get smooth changes (animation). I have made the number of points and the maximum delta speed for each bound to a pair of range sliders. I wanted to remove and add "at the end" but it was too late in the night for my brain to figure out how to do that. Later I guess.. :-)