createCanvas(400, 400);

  background(0);

  noStroke();

  colorMode(HSB, width, 100, 100);

}

function draw() {

  //  Init

  let diam = width;

  //  Test

  let circleHue = frameCount % 400;

  while(diam > 0) {

     //  Statement

    fill(circleHue, 100, 100);

    ellipse(width/2, height/2, diam);

    //  Update

    diam = diam - 20;

    circleHue = circleHue + 20;

    if(circleHue > width) {

      circleHue = 0;

    }

  }

}