createCanvas(windowWidth, windowHeight);

}

​

let xVel = 4;

let cRadius = 30;

let xPos = cRadius;

​

function draw() {

  background(220, 20, 120);

  ellipse(xPos, height / 2, 2 * cRadius);

  xPos = xPos + xVel;

​

  if (xPos > width - cRadius || xPos < cRadius) {

    xVel *= -1;

  }

}

​