Bouncing Ball - The Essential Guide to HTML5 - page 92

Code Explanation

var cwidth = 400;

var cheight = 300;

var ballrad = 10;

var boxx = 20;

var boxy = 30;

var boxwidth = 350;

var boxheight = 250;

var boxboundx = boxwidth+boxx-ballrad;

var boxboundy = boxheight+boxy-ballrad;

var inboxboundx = boxx+ballrad;

var inboxboundy = boxy+ballrad;

var ballx = 50;

var bally = 60;

var ctx;

var ballvx = 4;

var ballvy = 8;

function init(){

ctx = document.getElementById('canvas').
getContext('2d');

ctx.lineWidth = ballrad;

moveball();