let r = 50; let num = 50; let t = 0; let a = 0;

let radius = [];

​

function setup() {

  createCanvas(400, 400);

  angleMode(DEGREES);

}

​

function draw() {

  background(220);

  translate(width/2, height/2);

  noFill();

  beginShape();

  for (let i=0; i<num; i++) {

    angles[i] = (i/num-1) * 180; 

    startingAngles[i] = 360/num*i;

    radius[i] = map(r*cos(angles[i] + t), -r, r, 50, 100);

    let cx = radius[i]*cos(a + startingAngles[i]);

    let cy = radius[i]*sin(a + startingAngles[i]);

    // line(0, 0, cx, cy);

    vertex(cx, cy);

  }

  endShape(CLOSE);

  // a += 0.1;

  t += 1;

}