var y = 0;

var xspeed = 3;

var yspeed = 3;

​

function setup() {

  createCanvas(600, 400);

}

​

function draw() {

  background(255, 255, 0);

  display();

  upNdown();

  move();

}

​

function display() {

  stroke(0);

  strokeWeight(4);

  noFill();

  ellipse(x, 200, 64, 64);

  ellipse(300, y, 64, 64);

}

​

function upNdown() {

  if (x > width || x < 0) {

    xspeed = xspeed * -1;

  }

  if (y > height || y < 0) {

    yspeed = yspeed * -1;

  }

}

​

function move() {

  x = x + xspeed;

  y = y + yspeed;

}