var bird_nums = 2;	
var bird_speed = 100;	
var bird_step = 20;	
var bird_count = 0;		
var bird_image = null;		
var bird_posX = null;		
var bird_posY = null;		
var bird_direct = null;	
var bird_id = "birdspan";	
var bird_name = "birdimage";
var bird_width = 0;		
var bird_height = 0;		
var browser_ie = "IE";		
var browser_nn = "NN";		
function bird_moveobject()
{
	var xf, yf;
	var theta;
	var docx, docy;
	var docw, doch;

	if (bird_browser == browser_ie)
	{
		docx = document.body.scrollLeft;
		docy = document.body.scrollTop;
		docw = document.body.clientWidth  - bird_width;
		doch = document.body.clientHeight - bird_height;
	}
	else
	if (bird_browser == browser_nn)
	{
		docx = window.pageXOffset;
		docy = window.pageYOffset;
		docw = window.innerWidth  - bird_width;
		doch = window.innerHeight - bird_height;
	}
	for(bird_count=0; bird_count<bird_nums; bird_count++)
	{
		bird_direct[bird_count] += Math.floor(3*Math.random()) - 1;
		if (bird_direct[bird_count] <  0) bird_direct[bird_count] = 23;
		if (bird_direct[bird_count] > 23) bird_direct[bird_count] =  0;
		theta = bird_direct[bird_count] * 15 * 2 * 3.141592 / 360.0;
		xf =  Math.cos(theta) * bird_step;
		yf = -Math.sin(theta) * bird_step;

		if (bird_posX[bird_count] + xf < docx)      bird_posX[bird_count] = docx+docw;
		if (bird_posX[bird_count] + xf > docx+docw) bird_posX[bird_count] = docx;
		if (bird_posY[bird_count] + yf < docy)      bird_posY[bird_count] = docy+doch;
		if (bird_posY[bird_count] + yf > docy+doch) bird_posY[bird_count] = docy;

		bird_posX[bird_count] = bird_posX[bird_count] + xf;
		bird_posY[bird_count] = bird_posY[bird_count] + yf;

		if (bird_browser == browser_ie)
		{
			document.all(bird_id+bird_count).style.posLeft = bird_posX[bird_count];
			document.all(bird_id+bird_count).style.posTop  = bird_posY[bird_count];
			document.images[bird_name+bird_count].src = bird_image[bird_direct[bird_count]].src;
		}
		else
		if (bird_browser == browser_nn)
		{
			document.layers[bird_id+bird_count].moveTo(bird_posX[bird_count], bird_posY[bird_count]);
			document.layers[bird_id+bird_count].document.images[bird_name+bird_count].src = bird_getfile(bird_direct[bird_count]*15);
		}
	}
	setTimeout( "bird_moveobject();", bird_speed );
}

function bird_timerstart()
{
	if (bird_browser == browser_ie || bird_browser == browser_nn)
	{
		setTimeout( "bird_moveobject()", bird_speed );
	}
}

function bird_getfile(bird_angle)
{
	var fname;
	if (bird_angle < 10) {
		fname = "images/bird00" + bird_angle + ".gif";
	} else if (bird_angle < 100) {
		fname = "images/bird0" + bird_angle + ".gif";
	} else {
		fname = "images/bird" + bird_angle + ".gif";
	}
	return fname;
}

function bird_makelayout()
{
	var image_count;
	if (bird_browser == browser_ie)
	{
		document.write("<span id='dummy" +image_count+ "' style='visibility:hidden;'>");
		for(image_count=0; image_count<24; image_count++)
		{
			document.write("<img src='" +bird_getfile(image_count*15)+ "' WIDTH=1 HEIGHT=1>");
		}
		document.write("</span>");

		for(bird_count=0; bird_count<bird_nums; bird_count++)
		{
			document.write("<span id='" +bird_id+bird_count+ "' style='position:absolute;'>");
			document.write("<img src='" +bird_image[0].src+ "' id='" + bird_name+bird_count+ "' name='" +bird_name+bird_count+ "'>");
			document.write("</span>");
		}
	}
	else
	if (bird_browser == browser_nn)
	{
		document.write("<layer id='dummy' width=0 height=0>");
		for(image_count=0; image_count<24; image_count++)
		{
			document.write("<img src='" +bird_getfile(image_count*15)+ "' WIDTH=1 HEIGHT=1>");
		}
		document.write("</layer>");

		for(bird_count=0; bird_count<bird_nums; bird_count++)
		{
			document.write("<layer id='" +bird_id+bird_count+ "'>");
			document.write("<img src='" +bird_image[0].src+ "' id='" + bird_name+bird_count+ "' name='" +bird_name+bird_count+ "'>");
			document.write("</layer>");
		}
	}
}

function bird_standby()
{
	var docx, docy;
	var docw, doch;
	if (bird_browser == browser_ie)
	{
		for(bird_count=0; bird_count<bird_nums; bird_count++)
		{
			if (document.all(bird_id+bird_count).clientWidth  > bird_width ) bird_width  = document.all(bird_id+bird_count).clientWidth;
			if (document.all(bird_id+bird_count).clientHeight > bird_height) bird_height = document.all(bird_id+bird_count).clientHeight;
		}
		docx = document.body.scrollLeft;
		docy = document.body.scrollTop;
		docw = document.body.clientWidth  - bird_width;
		doch = document.body.clientHeight - bird_height;
	}
	else
	if (bird_browser == browser_nn)
	{
		for(bird_count=0; bird_count<bird_nums; bird_count++)
		{
			if (document.layers[bird_count].clip.width  > bird_width ) bird_width  = document.layers[bird_count].clip.width;
			if (document.layers[bird_count].clip.height > bird_height) bird_height = document.layers[bird_count].clip.height;
		}
		docx = window.pageXOffset;
		docy = window.pageYOffset;
		docw = window.innerWidth  - bird_width;
		doch = window.innerHeight - bird_height;
	}
	for(bird_count=0; bird_count<bird_nums; bird_count++)
	{
		bird_direct[bird_count] = Math.floor(24*Math.random());
		bird_posX[bird_count]   = docx + Math.floor(docw*Math.random());
		bird_posY[bird_count]   = docy + Math.floor(doch*Math.random());
	}
}
function bird_initialize()
{
	if (document.layers)
	{
		bird_browser = browser_nn;
	}
	else
	if (document.all)
	{
		bird_browser = browser_ie;
	}

	bird_posX   = new Array();
	bird_posY   = new Array();
	bird_direct = new Array();
	bird_image  = new Array();
	for(bird_count=0; bird_count<bird_nums; bird_count++)
	{
		bird_posX[bird_count] = 0;
		bird_posY[bird_count] = 0;
		bird_direct[bird_count] = 0;
	}
	for(image_count=0; image_count<24; image_count++)
	{
		bird_image[image_count] = new Image();
		bird_image[image_count].src = bird_getfile(image_count*15);
	}
}

function bird_main()
{
	bird_standby();		
	bird_timerstart();	
}