var time;



function setup() {

  createCanvas(windowWidth,

               windowHeight);

  noFill();

  strokeWeight(3);

  time = 0;

}



function draw() {

  background(0, 300, 300);



  for (var i = 0; i < 100; i = i + 1) {

    var ticktack = 1 + sin(time + i);

    stroke(100, 100, i * (255 / 10));

    strokeWeight(windowWidth / 35 * ticktack);

    ellipse(windowWidth / 2, windowHeight / 2, windowHeight / 10 * i);

  }



  time = time + 0.5;

}