createCanvas(windowWidth, windowHeight);

  initialize();

}

​

function initialize() {

  background(0);

  noFill();

  stroke(255);

  strokeWeight(2);

  let diameter = min(width, height);

  drawCircle(width / 2, height / 2, diameter);

}

​

function drawCircle(x, y, d) {

  circle(x, y, d);

​

  let new_d = d / 2;

​

  if (new_d >= 4) {

    drawCircle(x, y, new_d);

  }

}

​

function windowResized() {

  resizeCanvas(windowWidth, windowHeight);

  initialize();

}

​