let x;

​

// Declare a variable for the horizontal speed of the ball

let xspeed = 1;

​

function setup() {

  createCanvas(400, 400);

  // Initialize the position in the center

  x = width / 2;

}

​

function draw() {

  background(220);

​

  // Move the ball ball, either right or left

  x += xspeed;

  // Simplified Version:

  // When the ball is at either left or right border

  if (x <= 0 || x >= width) {

    // Flip the sign of the direction

    xspeed *= -1;

  }

​

  // Draw the ball

  ellipse(x, height / 2, 50, 50);

}

​