(function($) {
    $.fn.scrollBox = function(options){
        var defaultOptions = {
            speed: 0.1, //加速
            time: 16,   //移动速度
            top: 200,   //默认顶部
            align: 'right', //浮动位置，可选左、右
            mix: 0          //边距
        };
        
        var options = $.extend(defaultOptions, options);

        this.each(function(){
            var obj = $(this);
            init();
            
            function init(){
                obj.css('display', 'block');
                obj.css('position', 'absolute');
                obj.css(options.align, options.mix);
                obj.css('top', options.top+'px');
                obj.css('z-index', '99');
                
                move();
            }

            function back() {
	            acceleration = options.speed;
	            time = options.time;
	            var x1 = 0;
	            var y1 = 0;
	            var x2 = 0;
	            var y2 = 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;
	            }
	            var x = Math.max(x1, x2);
	            var y = Math.max(y1, y2);
	            var speed = acceleration;
	            return {
		            l: x,
		            t: y,
		            s: speed
	            };
	        };
    	    
            function move(){
                var tip = obj;
                var old = options.top;
                var pos = back().t;

                pos = pos - $(tip).Coordinate().y + options.top;
                pos = $(tip).Coordinate().y + pos / 10;
                if (pos < options.top) {
                    pos = options.top;
                }
                if (pos != old) {
                    tip.css('top',pos + "px");
                }
                old = pos;
                window.setTimeout(function(){move();}, options.time);
            };
        });
    };

    $.fn.Coordinate = function(){
        var E = $(this)[0];
		var C = E.offsetTop;
		var B = E.offsetLeft;
		var A = E.offsetWidth;
		var D = E.offsetHeight;
		while (E = E.offsetParent) {
			C += E.offsetTop;
			B += E.offsetLeft;

		}
		return {
			x: B,
			y: C,
			w: A,
			h: D
		};
    };
})(jQuery);