Simple code. Interesting pattern.

line(.5 * radius * cos(frameCount * .0001) + (frameCount * .01)%width,
.5 * radius * sin(frameCount * .001) + sin(frameCount * .04) + height/2,
-.5 * radius * cos(frameCount * .0001) + (frameCount * .01)%width,
-.5 * radius * sin(frameCount * .001) + sin(frameCount * .04) + height/2);