var viewportwidth=0;
var viewportheight=0;
var dir=0;
var glide_mover=0;
var glider_step=1;

var minheight=60;
var maxheight=180;

function glide()
{
	if(dir==0)
	{
		if(parseInt(document.getElementById('glider').style.left)<viewportwidth+50)
		{
			document.getElementById('glider').style.left=parseInt(document.getElementById('glider').style.left)+glider_step+"px";

			up=Math.random();
			if(up>0.5 && parseInt(document.getElementById('glider').style.top)>minheight)
				document.getElementById('glider').style.top=parseInt(document.getElementById('glider').style.top)-glider_step+"px";
			else
			{
				if(parseInt(document.getElementById('glider').style.top)<maxheight)
					document.getElementById('glider').style.top=parseInt(document.getElementById('glider').style.top)+1+"px";
			}

		}
		else
		{
			document.getElementById('glider').innerHTML="<img src=\""+ smf_images_url + "/trex2.png\" height=\"34px\" width=\"120px\">";
			dir=1;
		}
	}
	else
	{
		if(parseInt(document.getElementById('glider').style.left)>-50)
		{
			document.getElementById('glider').style.left=parseInt(document.getElementById('glider').style.left)-glider_step+"px";

			up=Math.random();
			if(up>=0.5 && parseInt(document.getElementById('glider').style.top)>minheight)
				document.getElementById('glider').style.top=parseInt(document.getElementById('glider').style.top)-glider_step+"px";
			else
			{
				if(parseInt(document.getElementById('glider').style.top)<maxheight)
					document.getElementById('glider').style.top=parseInt(document.getElementById('glider').style.top)+1+"px";
			}
		}
		else
		{
			document.getElementById('glider').innerHTML="<img src=\""+ smf_images_url + "/trex.png\" height=\"34px\" width=\"120px\">";
			dir=0;
		}
	}

}

function GetViewPort()
{
	if (typeof window.innerWidth != 'undefined')
	{
    	viewportwidth = window.innerWidth;
      	viewportheight = window.innerHeight;
 	}
 
	// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)

 	else 
	{
 		if (typeof document.documentElement != 'undefined' && typeof document.documentElement.clientWidth !='undefined' && document.documentElement.clientWidth != 0)
	 	{
    		viewportwidth = document.documentElement.clientWidth;
       		viewportheight = document.documentElement.clientHeight;
	 	}

 	// older versions of IE
 
	 	else
 		{
    		viewportwidth = document.getElementsByTagName('body')[0].clientWidth;
	       	viewportheight = document.getElementsByTagName('body')[0].clientHeight;
 		}
	}
}

GetViewPort();
glide_mover=setInterval("glide();",5);