let n = 100;

let m = 1.25;

​

function setup() {

  createCanvas(800, 800);

  background(255);

  ellipse(width/2,width/2,width*r,width*r);

}

​

function draw() {

  if (frameCount<(n*4)){

    stroke(0,255);

    strokeWeight(0.5);

  } else {

    stroke(0,0);

    strokeWeight(1.0);

  }

  translate(width/2,height/2);

  let x1 = r*width/2*cos(frameCount/n*2*PI);

  let y1 = r*width/2*sin(frameCount/n*2*PI);

  let x2 = r*width/2*cos((frameCount*m)/n*2*PI);

  let y2 = r*width/2*sin((frameCount*m)/n*2*PI);  

  line(x1,y1,x2,y2);

}