​

function setup() {

  x = false;

  createCanvas(600, 400);

}

​

function draw() {

  noStroke();

​

  // show background based on value of buttoncOn

​

  if (x) {

    background(255);

  } else {

    background(0);

  }

}

function mousePressed() {

  x = !x;

}

// ! means logical NOT. Pressing the mouse makes X become true

​