createCanvas(400, 400);

    background(40);

    noStroke();

    fill(255, 50);

}

​

function draw() {

    // no mirror

  ellipse(mouseX, mouseY, 10, 10);

    // mirror horizontally

    ellipse(width-mouseX, mouseY, 10, 10);

    // mirror vertically

    ellipse(mouseX, height-mouseY, 10, 10);

    // mirror both

    ellipse(width-mouseX, height-mouseY, 10, 10);

}