$(document).ready(function () { //perform actions when DOM is ready
    var z = 0; //for setting the initial z-index's
    var inAnimation = false; //flag for testing if we are in a animation

    $('#pictures img').each(function () { //set the initial z-index's
        z++; //at the end we have the highest z-index value stored in the z variable
        $(this).css('z-index', z); //apply increased z-index to <img>
    });

    function swapFirstLast(isFirst) {
        if (inAnimation) return false; //if already swapping pictures just return
        else inAnimation = true; //set the flag that we process a image

        var processZindex, direction, newZindex, inDeCrease; //change for previous or next image

        if (isFirst) { processZindex = z; direction = '-'; newZindex = 1; inDeCrease = 1; } //set variables for "next" action
        else { processZindex = 1; direction = ''; newZindex = z; inDeCrease = -1; } //set variables for "previous" action

        $('#pictures img').each(function () { //process each image
            if ($(this).css('z-index') == processZindex) { //if its the image we need to process
                $(this).animate({ 'top': direction + $(this).height() + 'px' }, 'slow', function () { //animate the img above/under the gallery (assuming all pictures are equal height)
                    $(this).css('z-index', newZindex) //set new z-index
            .animate({ 'top': '0' }, 'slow', function () { //animate the image back to its original position
                        inAnimation = false; //reset the flag
                    });
                });
            } else { //not the image we need to process, only in/de-crease z-index
                $(this).animate({ 'top': '0' }, 'slow', function () { //make sure to wait swapping the z-index when image is above/under the gallery
                    $(this).css('z-index', parseInt($(this).css('z-index')) + inDeCrease); //in/de-crease the z-index by one
                });
            }
        });

        return false; //don't follow the clicked link
    }

    $('#next a').click(function () {
        return swapFirstLast(true); //swap first image to last position
    });

    $('#prev a').click(function () {
        return swapFirstLast(false); //swap last image to first position
    });


    var intervalID = setInterval(myFunction, 3000);

    function myFunction() {
        return swapFirstLast(true);
    };


    $("#pictures img").hover(function () {

        window.clearInterval(intervalID)
    },
    function () {
        intervalID = setInterval(myFunction, 3000);
    });



});