var menu_height = 0;
var now_margin = 0;
var target_margin = 0;
var timer = -1;

window.onload = function() {
	Position.prepare();
	menu_height = Position.cumulativeOffset($('MoveMenu'))[1];
	Event.observe(window, 'scroll', onScroll);
}

function onScroll(e) {
	var scr = getScrollPosY();
	var tmp = scr - menu_height;
	if (tmp < 0) {
		tmp = 0;
	}
	target_margin = tmp;
	if (timer == -1) {
		timer = setInterval("resize()", 15);
	}
}

function resize() {
	if (now_margin > target_margin) {
		now_margin -= 5;
		if (now_margin < target_margin) {
			now_margin = target_margin;
		}
	} else if (now_margin < target_margin) {
		now_margin += 5;
		if (now_margin > target_margin) {
			now_margin = target_margin;
		}
	} else {
		clearTimeout(timer);
		timer = -1;
	}
	$('MoveMenu').style.height = now_margin + "px";
}

function getScrollPosY() {
	if (typeof window.pageYOffset != 'undefined') {
		return window.pageYOffset;
	} else if (typeof document.documentElement.scrollTop != 'undefined' && document.documentElement.scrollTop > 0) {
		return document.documentElement.scrollTop;
	} else if (typeof document.body.scrollTop != 'undefined') {
		return document.body.scrollTop;
	}
	return 0;
}

function getHeight() {
	if (typeof document.documentElement.clientHeight != 'undefined') {
		return document.documentElement.clientHeight;
	} else if (typeof document.body.clientHeight != 'undefined') {
		return document.body.clientHeight;
	} else if (typeof window.innerHeight != 'undefined') {
		return window.innerHeight;
	}
	return 0;
}