(function( $ ) {
    var stop;
    var index;

    var slides;

    $.fn.slider = function() {
        slides = this.find(".slide");

        index = 0;
        stop = slides.size;
    };

    $.fn.back = function() {
        var lastindex = index;

        if(index == 0)
            index = slides.size;
        else
            index--;


        slides[lastindex].addClass('hidden');
        slides[index].removeClass('hidden');
    }

    $.fn.next = function() {
        var lastindex = index;

        alert(index);

        if(index == stop)
            index = 0;
        else
            index++;

        slides[lastindex].addClass('hidden');
        slides[index].removeClass('hidden');
    }

}( jQuery ));