<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3c.org/1999/xhtml">
<head>
<title>Cursor-following canvas circles</title>
<style type='text/css'>
* {
margin:0;
padding:0;
}
canvas {
position:absolute;
top:50%;
left:50%;
margin-top:-200px;
margin-left:-320px;
border:1px solid #000;
}
</style>
<script type='text/javascript'>
function getwh() {
if (self.innerHeight) {
h=self.innerHeight
w=self.innerWidth
}
else if (document.documentElement && document.documentElement.clientHeight) {
h=document.documentElement.clientHeight
w=document.documentElement.clientHeight
}
else if (document.body) {
h=document.body.clientHeight
w=document.body.clientWidth
}
}
function ani() {
var ctx = document.getElementById('canvas').getContext('2d');
ctx.clearRect(0,0,640,400);
for (var i=0;i<num;i++) {
ctx.beginPath();
ctx.arc(a[i],b[i],c[i],0,Math.PI*2,true);
ctx.stroke();
nc=c[i]+Math.floor(Math.random()*3)-1
if (nc<minr) nc=minr
else if (nc>maxr) nc=maxr
c[i]=nc
nb=Math.floor(Math.random()*(diff*2+1))-diff+y
if (nb<c[i]) nb=c[i]
else if (nb>400-c[i]) nb=400-c[i]
b[i]=nb
na=Math.floor(Math.random()*(diff*2+1))-diff+x
if (na<c[i]) na=c[i]
else if (na>640-c[i]) na=640-c[i]
a[i]=na
}
setTimeout("ani()",40)
}
function load() {
x=320
y=200
maxr=75
minr=25
diff=10
num=10
a=new Array()
b=new Array()
c=new Array()
for (var i=0;i<num;i++) {
c[i]=Math.floor(Math.random()*50)+25
b[i]=Math.floor(Math.random()*(400-c[i]*2))+c[i]
a[i]=Math.floor(Math.random()*(640-c[i]*2))+c[i]
}
ani()
}
function mc(e) {
getwh()
x=Math.floor(e.pageX-(w-642)/2-2)
y=Math.floor(e.pageY-(h-402)/2-2)
}
window.onload=load
document.onmousemove=mc
</script>
</head>
<body>
<canvas id='canvas' width='640' height='400'></canvas>
</body>
</html>