Code tạo hiệu ứng Sao rơi theo trỏ chuột

<!-- Sao tuyết rơi theo trỏ chuột -->
<script type='text/javascript'> 
// <![CDATA[ 
var colour="#EF6B7B"; // Mã màu sao rơi
var sparkles=80; 
var x=ox=400; 
var y=oy=300; 
var swide=800; 
var shigh=600; 
var sleft=sdown=0; 
var tiny=new Array(); 
var star=new Array(); 
var starv=new Array(); 
var starx=new Array(); 
var stary=new Array(); 
var tinyx=new Array(); 
var tinyy=new Array(); 
var tinyv=new Array(); 

window.onload=function() { if (document.getElementById) { 

var i, rats, rlef, rdow; 

for (var i=0; i<sparkles; i++) { 

var rats=createDiv(3, 3); 

rats.style.visibility="hidden"; 

document.body.appendChild(tiny[i]=rats); 

starv[i]=0; 

tinyv[i]=0; 

var rats=createDiv(5, 5); 

rats.style.backgroundColor="transparent"; 

rats.style.visibility="hidden"; 

var rlef=createDiv(1, 5); 

var rdow=createDiv(5, 1); 

rats.appendChild(rlef); 

rats.appendChild(rdow); 

rlef.style.top="2px"; 

rlef.style.left="0px"; 

rdow.style.top="0px"; 

rdow.style.left="2px"; 

document.body.appendChild(star[i]=rats);}set_width(); 

sparkle();}} 

function sparkle() {var c; 

if (x!=ox || y!=oy) { 

ox=x;oy=y; 

for (c=0; c<sparkles; c++) if (!starv[c]) { 

star[c].style.left=(starx[c]=x)+"px"; 

star[c].style.top=(stary[c]=y)+"px"; 

star[c].style.clip="rect(0px, 5px, 5px, 0px)"; 

star[c].style.visibility="visible"; 

starv[c]=50; 

break;}}for (c=0; c<sparkles; c++) { 

if (starv[c]) update_star(c); 

if (tinyv[c]) update_tiny(c);} 

setTimeout("sparkle()", 40);}function update_star(i) { 

if (--starv[i]==25) star[i].style.clip="rect(1px, 4px, 4px, 1px)"; 

if (starv[i]) { 

stary[i]+=1+Math.random()*3; 

if (stary[i]<shigh+sdown) { 

star[i].style.top=stary[i]+"px"; 

starx[i]+=(i%5-2)/5; 

star[i].style.left=starx[i]+"px";}else { 

star[i].style.visibility="hidden"; 

starv[i]=0; 

return;}}else {tinyv[i]=50; 

tiny[i].style.top=(tinyy[i]=stary[i])+"px"; 

tiny[i].style.left=(tinyx[i]=starx[i])+"px"; 

tiny[i].style.width="2px"; 

tiny[i].style.height="2px"; 

star[i].style.visibility="hidden"; 

tiny[i].style.visibility="visible"}} 

function update_tiny(i) { 

if (--tinyv[i]==25) { 

tiny[i].style.width="1px"; 

tiny[i].style.height="1px";} 

if (tinyv[i]) { 

tinyy[i]+=1+Math.random()*3; 

if (tinyy[i]<shigh+sdown) { 

tiny[i].style.top=tinyy[i]+"px"; 

tinyx[i]+=(i%5-2)/5; 

tiny[i].style.left=tinyx[i]+"px";}else { 

tiny[i].style.visibility="hidden"; 

tinyv[i]=0; 

return;}}else tiny[i].style.visibility="hidden";} 

document.onmousemove=mouse; 

function mouse(e) { 

set_scroll(); 

y=(e)?e.pageY:event.y+sdown; 

x=(e)?e.pageX:event.x+sleft;} 

function set_scroll() { 

if (typeof(self.pageYOffset)=="number") { 

sdown=self.pageYOffset; 

sleft=self.pageXOffset;} 

else if (document.body.scrollTop || document.body.scrollLeft) { 

sdown=document.body.scrollTop; 

sleft=document.body.scrollLeft;} 

else if (document.documentElement && (document.documentElement.scrollTop || document.documentElement.scrollLeft)) { 

sleft=document.documentElement.scrollLeft; 

sdown=document.documentElement.scrollTop;}else {sdown=0;sleft=0;}} 

window.onresize=set_width; 

function set_width() { 

if (typeof(self.innerWidth)=="number") { 

swide=self.innerWidth; 

shigh=self.innerHeight;} 

else if (document.documentElement && document.documentElement.clientWidth) { 

swide=document.documentElement.clientWidth; 

shigh=document.documentElement.clientHeight;}else if (document.body.clientWidth) { 

swide=document.body.clientWidth; 

shigh=document.body.clientHeight;}} 

function createDiv(height, width) { 

var div=document.createElement("div"); 

div.style.position="absolute"; 

div.style.height=height+"px"; 

div.style.width=width+"px"; 

div.style.overflow="hidden"; 

div.style.backgroundColor=colour; 

return (div);}
// ]]> 
</script>