Choose your values for r1, r2 to draw an ellipse (as in project http://scratch.mit.edu/projects/41640002/). Ellipses are then drawn with the same centre but rotated by 'step' degrees. Once a complete figure is drawn it is rotated. Changes to r1, r2 and step will immediately change the drawn figure.
Inspired by @hppavilion asking for help with with angled ellipses. All done with the pen.
