var oAnimate    = document.getElementById("ID_ANIMATE");

var nWidth      = oAnimate.offsetWidth;
var nHeight     = oAnimate.offsetHeight;
var nFSize      = 9;
var nCount      = 30;
var nMaxSpeed   = 4;
var strFlakeURL = "img/snowflake.gif";

// --

var aoFlakes    = new Array(nCount);

// --

function UpdateFlakePos(nNum)
{
     var oImg = aoFlakes[nNum];
     oImg.style.top = oImg.m_nY.toString(10) + "px";
     oImg.style.left = oImg.m_nX.toString(10) + "px";
}

function ResetFlake(nNum, bRandY)
{
     var oImg = aoFlakes[nNum];

     oImg.m_nX           = Math.ceil(Math.random() * nWidth);
     oImg.m_nY           = bRandY ? Math.ceil(Math.random() * nHeight) : -nFSize;
     oImg.m_nSpeed       = Math.ceil(Math.random() * nMaxSpeed) + 1;
}

function OnTimer()
{
     for(var i = 0; i < nCount; i++)
     {
         var oImg = aoFlakes[i];

         oImg.m_nX += Math.ceil(Math.random() * 3 - 2);
         oImg.m_nY += oImg.m_nSpeed;

         if(oImg.m_nY > nHeight)
             ResetFlake(i, false);

         UpdateFlakePos(i);
     }
}

// --

for(var i = 0; i < nCount; i++)
{
     var oImg = document.createElement("IMG");

     oImg.src = strFlakeURL;
     oAnimate.appendChild(oImg);

     aoFlakes[i] = oImg;

     ResetFlake(i, true);
     UpdateFlakePos(i);
}

window.setInterval(OnTimer, 50);