createCanvas(300, 400)

  background("black")

  noStroke()

}

​

function draw() {

  if (movedX !== 0 && movedY !== 0) {

    fill(random(256), random(256), random(256), 70)

    circle(mouseX, mouseY, random(3, 100))

  }

}

​

function mousePressed() {

  background("black")

}

​