let d;

let g;

function setup() {

  cnv = createCanvas(100, 100);

//  cnv.touchStarted(changeGray); // attach listener for

  // canvas click only

  d = 10;

  g = 100;

  background(g);

}

​

function draw() {

​

}

​

// this function fires with any touch anywhere

function touchStarted() {

  d = d + 10;

  ellipse(width / 2, height / 2, d, d);

}

​

// this function fires only when cnv is clicked

function changeGray() {

  g = random(0, 255);

}