you can move any of the 3 points around and the project should re-draw the intermediate "string-art" lines as needed - you may need to move the ball and allow the redraws to happen as you move it, I've used "broadcast and wait" rather than "broadcast" so that the code isn't trying to re-draw to moving end points. You can change the variable "numberOfPoints" in the code to see a lower or higher number of mid-points between the 2 lines between the 3 points. The "string art" effect creates a smooth parabola connecting the end points as the number of points along the lines gets higher.
This is a sample of the "Pixar in a Box" project over on https://www.khanacademy.org/partner-content/pixar/environment-modeling-2/animating-parabolas-ver2/p/string-art-construction which is quite pretty and a lot of fun in conjunction with the discussion of the Pixar materials over on Khan Academy
