Bouncing Ball - The Essential Guide to HTML5 - page 93

Code Explanation

setInterval(moveball,100);

}

function moveball(){

ctx.clearRect(boxx,boxy,boxwidth,boxheight);

moveandcheck();

ctx.beginPath();

ctx.fillStyle ="rgb(200,0,50)";

ctx.arc(ballx, bally, ballrad,0,Math.PI*2,true);

ctx.fill();

ctx.strokeRect(boxx,boxy,boxwidth,boxheight);

}

function moveandcheck() {

var nballx = ballx + ballvx;

var nbally = bally +ballvy;

if (nballx > boxboundx) {

ballvx =-ballvx;

nballx = boxboundx;

}

if (nballx < inboxboundx) {