let myY = 0;

​

//initialize variable for speed

let mySpeed = 1;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

  //use variable for x

  circle(200, myY,200);

  //reverse at bottom and top boundary

  if(myY > height || myY < 0){

    mySpeed = mySpeed*-1;

  }

  //add speed

  myY += mySpeed;

  //set size of text

  textSize(20);

  //display x location as text

  text("y = " + myY, 170, myY + 10);  

}