var y = 0;
var inc = 250;
var scroll;
var upOpacity;
var downOpacity;

window.addEvent('domready', function() {
	scroll = new Fx.Scroll('content_holder', {
		wait: false,
		duration: 1200
	});
	
	upOpacity = new Fx.Style('up','opacity', { duration: 500 } );
	downOpacity = new Fx.Style('down','opacity', { duration: 500 } );
	shippingOpacity = new Fx.Style('shipping_info_body','opacity', { duration: 250 } );
	
	if ($('down')) {
		$('down').addEvent('click',function(event) {
			event = new Event(event).stop();
			y += inc;
			runScroll();
		});
	}

	if ($('up')) {
		$('up').addEvent('click',function(event) {
			event = new Event(event).stop();
			y -= inc;
			runScroll();
		});
	}
	
	if ($('up') || $('down')) {
		scroll.scrollTo(0,y);
		
		if ($('content').getSize().size.y > 250) {
			$('slider_controls').style.visibility = 'visible';
			upOpacity.set(.2);		
		}
	}
});


function runScroll() {
	if (y < 0) y = 0;
	if ((y + 250) >= $('content').getSize().size.y) y = $('content').getSize().size.y - 250;

	scroll.scrollTo(0,y);

	if (!y) {
		upOpacity.start(.2);
	}
	else {
		upOpacity.start(1);
	}
	
	if ((y + 250) >= $('content').getSize().size.y) {
		downOpacity.start(.2);
	}
	else {
		downOpacity.start(1);
	}
}

function isNumberKey(evt) {
	var charCode = (evt.which) ? evt.which : event.keyCode
		
	if (charCode > 31 && (charCode < 48 || charCode > 57))
		return false;

	return true;
}