let speed= 3;

​

function setup() {

  createCanvas(600, 400);

}

​

function draw() {

  background(220);

  stroke (0);

  strokeWeight (3);

  noFill();

  ellipse (x, 200, 100, 100)

     x= x+speed

  if (x > width) {

    //print("OFF THE SCREEN!")

 speed= -3

  }

 else if (x<0) {

   speed=3

 }

    //and is like an intersection

    // or is having y happen if either x happens to be true

}