(function($) {
	$.extend($.fx.step,{
	    backgroundPosition: function(fx) {
            if (fx.state === 0 && typeof fx.end == 'string') {
                var start = $.curCSS(fx.elem,'backgroundPosition');
                start = toArray(start);
                fx.start = [start[0],start[2]];
                var end = toArray(fx.end);
                fx.end = [end[0],end[2]];
                fx.unit = [end[1],end[3]];
			}
            var nowPosX = [];
            nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
            nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
            fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];

           function toArray(strg){
               strg = strg.replace(/left|top/g,'0px');
               strg = strg.replace(/right|bottom/g,'100%');
               strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g,"$1px$2");
               var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
               return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
           }
        }
	});
})(jQuery);




/*Intaraction*/
$(function(){	   
	var tar =$('#index a'),st = -500,en = "(0px 0px)",en2 = "(-500px 0px)",d1 = 200,d2 = 500,d3 = 1000,line = {backgroundPosition: st+"px 0px"},ind = $("#index").fadeIn(d3);
	
	$(window).load(function(){ind})	   
	tar.css( line ).hover(
		function(){$(this).stop().animate({backgroundPosition:en}, {duration:d1})},
		function(){$(this).stop().animate({backgroundPosition:en2}, {duration:d2,complete:function(){$(this).css( line )}})
	})
});