let x;

​

function setup() {

  createCanvas(400, 400);

  // Initialize the position in the center

  x = width / 2;

}

​

function draw() {

  background(220);

​

  // When I'm at the left border

  if (x == 0) {

    // Go right

    x++;

  }

​

  // When I'm at the right border

  if (x == width) {

    console.log("YAY I've reached the right side!", x);

    // Go left

    x--;

    console.log("Now I'm going left.", x);

  }

​

  // Draw the ball

  ellipse(x, height / 2, 50, 50);

}

​