​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

  print(mouseX, mouseY);

  if (buttonDown) {

    fill(0); 

  } else {

    fill(255); 

  }

  rect(150, 150, 100, 100);

}

​

function mousePressed() {

​

  if (mouseX > 150 && mouseX < 250 && mouseY > 150 && mouseY < 250) {

    buttonDown = !buttonDown; 

  }

}

​