​

function setup() {

  createCanvas(600, 400);

}

​

function draw() {

  if (on) {

    background(255, 255, 0);

  } else {

    background(20);

  }

  stroke(255);

  strokeWeight(5);

  noFill();

  if (mouseX > 250 && mouseX < 350 && mouseY > 175 && mouseY < 225) {

    fill(180, 0, 100, 180);

  }

  rectMode(CENTER);

  rect(300, 200, 100, 50);

  if (mouseIsPressed) {

    if (mouseX > 250 && mouseX < 350 && mouseY > 175 && mouseY < 225) {

      background(20);

      fill(180, 0, 100, 255);

      rect(300, 200, 90, 40);

    }

  }

}

​

function mousePressed() {

  if (mouseX > 250 && mouseX < 350 && mouseY > 175 && mouseY < 225) {

    on = !on

  }

}