// ページの先頭へ
function backToTop() {
	var x1 = x2 = x3 = 0;
	var y1 = y2 = y3 = 0;
	if (document.documentElement) {
		x1 = document.documentElement.scrollLeft || 0;
		y1 = document.documentElement.scrollTop || 0;
	}
	if (document.body) {
		x2 = document.body.scrollLeft || 0;
		y2 = document.body.scrollTop || 0;
	}
	x3 = window.scrollX || 0;
	y3 = window.scrollY || 0;
	var x = Math.max(x1, Math.max(x2, x3));
	var y = Math.max(y1, Math.max(y2, y3));
	window.scrollTo(Math.floor(x * 0.9), Math.floor(y * 0.9));
	if (x > 0 || y > 0) {
		window.setTimeout("backToTop()", 10);
	}
}


var preloadImageArray = new Array();

function pushImage(imageSrc){
	var image = new Image();
	image.src = imageSrc;
	preloadImageArray.push(image);
}

function swapBackground(obj){
	if(arguments[1] == null){
		obj.style.background = obj["tmp"];
	}
	else{
		obj["tmp"] = obj.style.background;
		obj.style.background = "url("+ arguments[1] +")";
	}
}

function preload(){
	var path = "/img/";
	pushImage(path + "menu_top.jpg");
	pushImage(path + "menu_story.jpg");
	pushImage(path + "menu_character.jpg");
	pushImage(path + "menu_download.jpg");
	pushImage(path + "menu_contact.jpg");
	pushImage(path + "goto_top.jpg");
}

window.onload = function(){
	preload();
}