let speedX = 1;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

}

​

function draw() {

  background(220);

​

  posX = posX + speedX;

​

  if (posX < 25 || posX > width-25) {

    console.log('bounce');

    speedX = speedX * -1;

  }

  ellipse(posX, 200, 50, 50);

}

​