function gameFullScreen () {

	xwidth = $(document.body).getSize().x;
	xheight = $(document.body).getSize().y;
	availx = xwidth-300;
	availy = Math.round (availx / (640/480));
	if (availy+100 > xheight) {
		availy = xheight-50;
		availx = Math.round((640/480) * availy);
	}

	posx = Math. round ((xwidth-availx)/2);
	try {
		oldx = $('myContent').getPosition().x;
		oldy = $('myContent').getPosition().y;
	} catch (e) {
		oldx = 0;
		oldy = 0;
	}
	if (!$chk($('curtain_div'))) {
		rBody = $(document.body);
	   rCurtainDiv = document.createElement ('div');
	   rBody.appendChild (rCurtainDiv);
	   rCurtainDiv.setAttribute ('id', 'curtain_div');
		with ($('curtain_div').style) {
			display = 'none';
			position = 'absolute';
			top = '0px';
			left = '0px';
			width = rBody.getScrollSize().x+'px';
			height = rBody.getScrollSize().y+'px';
			backgroundColor = 'black';
			zIndex = '900';
			textAlign = 'center';
			verticalAlign = 'top';
		}
		$('curtain_div').innerHTML = '<div style="float:right;color:white;padding-right:8px;padding-top:3px;font-family:arial;font-size:9px;cursor:pointer">zamknij</div>';
		$('curtain_div').setOpacity(0);
	   $('curtain_div').addEvent('click',
			function (event) {
				with ($('myContent').style) {
					width = '640px';
					height = '480px';
					position = 'relative';
					left = '0px';
					top = '0px';
				}
				var myFx = new Fx.Morph ('curtain_div', {
					duration: 200,
					onComplete: function() {
						$('curtain_div').setStyle('display','none');
					}
				});
				myFx.start ({
				 'opacity': 0
				});
			}
	   );
	}

		$('curtain_div').setOpacity(0);
		$('curtain_div').setStyle('display','block');
		var myFx = new Fx.Morph ('curtain_div', {
		duration: 1000,
		onComplete: function () {
			with ($('myContent').style) {
				width = availx+'px';
				height = availy+'px';
				position = 'absolute';
				left = posx+'px';
				top = 25+'px';
			}
		}
		});
		myFx.start({
			'opacity':[0,0.9]
		});

}