//

// By Jon Froehlich

// http://makeabilitylab.io

// 

// See:

//  - https://learning.oreilly.com/library/view/make-getting-started/9781457186769/ch08.html#motion

​

​

let x;

let y;

let xSpeed = 3; // moves 3 pixels per frame

let diameter = 40;

​

function setup() {

  createCanvas(400, 400);

  x = width / 2;

  y = height / 2;

  fill(200, 0, 0);

  noStroke();

}

​

function draw() {

  background(220);

  x += xSpeed;

  ellipse(x, y, diameter);

  // check to make sure it doesn't go offscreen

  let radius = diameter / 2;

  if(x - radius < 0 || x + radius > width){

    xSpeed = xSpeed * -1;

  }

}