let r, g, b;

​

var xpos = 100;

var speed = 1;

​

function setup() {

  createCanvas(400, 400);

  // Pick colors randomly

  r = random(255);

  g = random(255);

  b = random(255);

}

​

function draw() {

  background(127);

    xpos = xpos + speed;

​

  if ((xpos > width - 100) || (xpos < 100)) {

    speed = speed * -1;

  }

  // Draw a circle

  strokeWeight(2);

  stroke(r, g, b);

  fill(r, g, b, 127);

  ellipse(xpos, 200, 200);

}

​

// When the user clicks the mouse

function mousePressed() {

  // Check if mouse is inside the circle

  let d = dist(mouseX, mouseY, xpos, 200);

  if (d < 100) {

    // Pick new random color values

    r = random(255);

    g = random(255);

    b = random(255);

  }

}