createCanvas(windowWidth, windowHeight);

  background(31);

}

​

function draw() {

  noStroke();

  fill(63, 127, 255, 100);

  circle(mouseX, mouseY, 20);

  fill(255, 127, 63, 100);

  circle(width - mouseX, mouseY, 20);

  fill(255, 63, 127, 100);

  circle(width, height - mouseY, 20);

  fill(63, 255, 127, 100);

  circle(width - mouseX, height - mouseY, 20);

}