createCanvas(400, 400);

  background(0);

}

​

function draw() {

  stroke(255);

  strokeWeight(2);

  ellipse(30,20,30,20);

  if (mouseIsPressed){

    point(mouseX, mouseY);

    if(mouseX>15 && mouseX<45 && mouseY>10 && mouseY<30){

      background(0);

    }

  }

}