$(document).ready(
		function() {

			var $ul_list = $("#subdiv_item");
			var stop_pos = $ul_list.parent().height() - $ul_list.height();
			var animate_speed = 0.100;
			var $view_section = $("#view_section");

			function start_scroll(direction) {

				var cur_pos = $ul_list.position();
				var top_target;

				if (direction == "up") {
					top_target = 0;
				} else if (direction == "down") {
					top_target = stop_pos;
				} else {
					return false;
				}

				var animate_time = Math.abs(Math.abs(top_target)
						- Math.abs(cur_pos.top))
						/ animate_speed;

				$ul_list.animate( {
					top : top_target + "px"
				}, {
					duration : animate_time,
					complete : setup_scroll_button()
				});
			}

			function stop_scroll() {
				$ul_list.stop();
				setup_scroll_button();
			}

			function setup_scroll_button() {
				var cur_pos = $ul_list.position();

				if (cur_pos.top == 0) {

					$("#a_up").css( {
						visibility : "hidden"
					});
					$("#a_down").css( {
						visibility : "visible"
					});

				} else if (cur_pos.top == stop_pos) {

					$("#a_down").css( {
						visibility : "hidden"
					});
					$("#a_up").css( {
						visibility : "visible"
					});

				} else {
					$("#a_up, #a_down").css( {
						visibility : "visible"
					});
				}
			}

			$("#subdiv_item").parent().css( {
				overflow : "hidden"
			});
			if (stop_pos < 0) {
				$("#a_down").css( {
					visibility : "visible"
				});
			}

			$("#a_up").hover(function() {

				stop_scroll();
				start_scroll("up");

			}, function() {
				stop_scroll();
			});

			$("#a_down").hover(function() {

				stop_scroll();
				start_scroll("down");
			}, function() {
				stop_scroll();
			});

			$("#subdiv_item li a").hover(
					function() {
						var item_id = parseInt($(this).attr("id").replace(
								"item_", ""));
						var new_item = section_list[item_id];

						$view_section.children().fadeOut(
								"fast",
								function() {

									$view_section.find("h3").text(
											new_item.title).end()

									.find("div.picture img").attr("src",
											new_item.icon).attr("alt",
											new_item.title).end()

									.find("div.descr").html(" ").html(
											new_item.text).end();

									$view_section.children().fadeIn("slow");
								});

					}, function() {
					});

		});