let xspeed=1;

​

function setup() {

  createCanvas(400, 400);

  x= width/2

}

​

function draw() {

  background(220);

  //if you are outside of the boundary, turn around. right now we have hitting the boundary

  if (x > width || x<0) {

  xspeed+= -5;

  //move left

    //turn around to go left

​

  //move right

    //turn around to go right

  }

  //move

  //x speed can either be +1 or -1

  x= x+ xspeed

​

  ellipse(x, 200, 20, 20);

}