var ns4 = (document.layers)?true:false;
var ie5 = (document.all)?true:false;

var interval = 10; //Move 10px every initialization;

var x = interval;  //Starting Location - left;
var y = interval;  //Starting Location - top;

var dest_x = 0;
var dest_y = 0;

var maxwidth    = 0; // Window Width
var maxheight   = 0; // Window Height
var imagewidth  = 0; // Image Width
var imageheight = 0; // Image Height

var verDir = 'down';
var horDir = 'right';

var ufo;

function preloadImage($src){
	var img = new Image();
	img.src=$src;

	imagewidth  = img.width;
	imageheight = img.height;
}

function windowSize() {
	if( typeof(window.innerWidth) == 'number' ) {
		//Non-IE
		maxwidth = window.innerWidth;
		maxheight = window.innerHeight;
	} else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
		//IE 6+ in 'standards compliant mode'
		maxwidth = document.documentElement.clientWidth;
		maxheight = document.documentElement.clientHeight;
	} else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
		//IE 4 compatible
		maxwidth = document.body.clientWidth;
		maxheight = document.body.clientHeight;
	}

	maxwidth-=imagewidth;
	maxheight-=imageheight;
}

function moveImage(){
	// Vertical
	y=(verDir == 'down') ? ((y+interval)>dest_y) ? dest_y : (y+interval) : ((y-interval)<interval) ? interval : (y-interval);
	ufo.style.top=y+'px';

	if ((y==dest_y) && (verDir == 'down')) {
		dest_y=0;
		verDir='up';
		while ((dest_y>parseInt((maxheight/2))) || (dest_y<interval)) { dest_y=(parseInt((Math.random() * maxheight))); }
	} else if ((y==interval) && (verDir == 'up')) {
		verDir='down';
		while (dest_y<parseInt((maxheight/2))) { dest_y=(parseInt((Math.random() * maxheight))); }
	}

	x=(horDir == 'right') ? ((x+interval)>dest_x) ? dest_x : (x+interval) : ((x-interval)<interval) ? interval : (x-interval);
	ufo.style.left=x+'px';

	if ((x==dest_x) && (horDir == 'right')) {
		dest_x=0;
		horDir='left';
		while ((dest_x>parseInt((maxwidth/2))) || (dest_x<interval)) { dest_x=(parseInt((Math.random() * maxwidth))); }
	} else if ((x==interval) && (horDir == 'left')) {
		horDir='right';
		while (dest_x<parseInt((maxwidth/2))) { dest_x=(parseInt((Math.random() * maxwidth))); }
	}
}

function moveImageHorizontal(){
	x=(horDir == 'right') ? ((x+interval)>dest_x) ? dest_x : (x+interval) : ((x-interval)<interval) ? interval : (x-interval);
	ufo.style.left=x+'px';

	if ((x==dest_x) && (horDir == 'right')) {
		dest_x=0;
		horDir='left';
		dest_x=interval;
	} else if ((x==interval) && (horDir == 'left')) {
		horDir='right';
		dest_x=maxwidth;
	}
}


function start($id,$src,$opacity,$mode){
	ufo=document.getElementById ? document.getElementById($id) :
	    document.all ? document.all[$id] : document.layers[$id];

	preloadImage($src);
	windowSize();

	ufo.style.filter='alpha(opacity='+$opacity+');';
	setInterval('windowSize()',100);

	switch ($mode) {
		case 'both':
			ufo.style.top=y+'px';
			while (dest_y<parseInt((maxheight/2))){ dest_y=(parseInt((Math.random() * maxheight))); }

			ufo.style.left=x+'px';
			while (dest_x<parseInt((maxwidth/2))) { dest_x=(parseInt((Math.random() * maxwidth))); }

			setInterval('moveImage()', 250);
			break;
		case 'horizontal':
			ufo.style.left=x+'px';
			dest_x=maxwidth;

			setInterval('moveImageHorizontal()', 250);
			break;
	}
}