(function($) {

    $.fn.ko = function(callback, code) {
        if(code == undefined) code = "38,40,40,37,39,37,39,66";
       
        return this.each(function() {
            var kkeys = [];
            $(this).keydown(function(e)
            {
                kkeys.push( e.keyCode );
                if ( kkeys.toString().indexOf( code ) >= 0 ){
                    $(this).unbind('keydown', arguments.callee);
                    callback(e);
                }
            }, true);
        });
    }   
})(jQuery);

$(document).ready(function() {
   
    $(window).ko(function(){
        $("body").css("background", "url('http://media.giantbomb.com/uploads/0/25/11444-Donkey%20Kong_640_super.jpg')");
    });
   
});