let direction = 1;

​

let d2 = 0;

let direction2 = 1;

​

function setup() {

  createCanvas(400, 400);

  angleMode(DEGREES);

}

​

function draw() {

  background(220);

  noFill();

  strokeWeight(3);

  translate(width/2, height/2);

  rotate(180);

  let dis = 30+d;

  let dis2= 90+d2;

  if (dis > 180 || dis <= 0) {

    direction = direction * -1;

  }

  if (dis2 > 180 || dis2 <= 0) {

    direction2 = direction2 * -1;

  }

  arc(0, 0, 200, 200, 0, dis);

  arc(0, 0, 100, 100, 0, dis2);

  d = d + direction; 

  d2 = d2 + direction2;

}