/*!

* reveal.js
* http://lab.hakim.se/reveal-js
* MIT licensed
* Version 3.1.0
* Including modifocations to support margin left & height
*
* Copyright (C) 2015 Hakim El Hattab, http://hakim.se
*/

(function( root, factory ) {

if( typeof define === 'function' && define.amd ) {
    // AMD. Register as an anonymous module.
    define( function() {
        root.Reveal = factory();
        return root.Reveal;
    } );
} else if( typeof exports === 'object' ) {
    // Node. Does not work with strict CommonJS.
    module.exports = factory();
} else {
    // Browser globals.
    root.Reveal = factory();
}

}( this, function() {

'use strict';

var Reveal;

var SLIDES_SELECTOR = '.slides section',
    HORIZONTAL_SLIDES_SELECTOR = '.slides>section',
    VERTICAL_SLIDES_SELECTOR = '.slides>section.present>section',
    HOME_SLIDE_SELECTOR = '.slides>section:first-of-type',

// Configuration defaults, can be overridden at initialization time
    config = {

        // The "normal" size of the presentation, aspect ratio will be preserved
        // when the presentation is scaled to fit different resolutions
        width: 960,
        height: 700,

        // Factor of the display size that should remain empty around the content
        margin: 0.1,

        // Top and Left margins to reposition the slides
        marginTop: '',
        marginLeft: '',

        // Bounds for smallest/largest possible scale to apply to content
        minScale: 0.2,
        maxScale: 1.5,

        // Display controls in the bottom right corner
        controls: true,

        // Display a presentation progress bar
        progress: true,

        // Display the page number of the current slide
        slideNumber: false,

        // Push each slide change to the browser history
        history: false,

        // Enable keyboard shortcuts for navigation
        keyboard: true,

        // Optional function that blocks keyboard events when retuning false
        keyboardCondition: null,

        // Enable the slide overview mode
        overview: true,

        // Vertical centering of slides
        center: true,

        // Enables touch navigation on devices with touch input
        touch: true,

        // Loop the presentation
        loop: false,

        // Change the presentation direction to be RTL
        rtl: false,

        // Turns fragments on and off globally
        fragments: true,

        // Flags if the presentation is running in an embedded mode,
        // i.e. contained within a limited portion of the screen
        embedded: false,

        // Flags if we should show a help overlay when the questionmark
        // key is pressed
        help: true,

        // Flags if it should be possible to pause the presentation (blackout)
        pause: true,

        // Number of milliseconds between automatically proceeding to the
        // next slide, disabled when set to 0, this value can be overwritten
        // by using a data-autoslide attribute on your slides
        autoSlide: 0,

        // Stop auto-sliding after user input
        autoSlideStoppable: true,

        // Enable slide navigation via mouse wheel
        mouseWheel: false,

        // Apply a 3D roll to links on hover
        rollingLinks: false,

        // Hides the address bar on mobile devices
        hideAddressBar: true,

        // Opens links in an iframe preview overlay
        previewLinks: false,

        // Exposes the reveal.js API through window.postMessage
        postMessage: true,

        // Dispatches all reveal.js events to the parent window through postMessage
        postMessageEvents: false,

        // Focuses body when page changes visiblity to ensure keyboard shortcuts work
        focusBodyOnPageVisibilityChange: true,

        // Transition style
        transition: 'slide', // none/fade/slide/convex/concave/zoom

        // Transition speed
        transitionSpeed: 'default', // default/fast/slow

        // Transition style for full page slide backgrounds
        backgroundTransition: 'fade', // none/fade/slide/convex/concave/zoom

        // Parallax background image
        parallaxBackgroundImage: '', // CSS syntax, e.g. "a.jpg"

        // Parallax background size
        parallaxBackgroundSize: '', // CSS syntax, e.g. "3000px 2000px"

        // Amount of pixels to move the parallax background per slide step
        parallaxBackgroundHorizontal: null,
        parallaxBackgroundVertical: null,

        // Number of slides away from the current that are visible
        viewDistance: 3,

        // Script dependencies to load
        dependencies: []

    },

// Flags if reveal.js is loaded (has dispatched the 'ready' event)
    loaded = false,

// Flags if the overview mode is currently active
    overview = false,

// The horizontal and vertical index of the currently active slide
    indexh,
    indexv,

// The previous and current slide HTML elements
    previousSlide,
    currentSlide,

    previousBackground,

// Slides may hold a data-state attribute which we pick up and apply
// as a class to the body. This list contains the combined state of
// all current slides.
    state = [],

// The current scale of the presentation (see width/height config)
    scale = 1,

// CSS transform that is currently applied to the slides container,
// split into two groups
    slidesTransform = { layout: '', overview: '' },

// Cached references to DOM elements
    dom = {},

// Features supported by the browser, see #checkCapabilities()
    features = {},

// Client is a mobile device, see #checkCapabilities()
    isMobileDevice,

// Throttles mouse wheel navigation
    lastMouseWheelStep = 0,

// Delays updates to the URL due to a Chrome thumbnailer bug
    writeURLTimeout = 0,

// Flags if the interaction event listeners are bound
    eventsAreBound = false,

// The current auto-slide duration
    autoSlide = 0,

// Auto slide properties
    autoSlidePlayer,
    autoSlideTimeout = 0,
    autoSlideStartTime = -1,
    autoSlidePaused = false,

// Holds information about the currently ongoing touch input
    touch = {
        startX: 0,
        startY: 0,
        startSpan: 0,
        startCount: 0,
        captured: false,
        threshold: 40
    },

// Holds information about the keyboard shortcuts
    keyboardShortcuts = {
        'N  ,  SPACE':                      'Next slide',
        'P':                                        'Previous slide',
        '←  ,  H':            'Navigate left',
        '→  ,  L':            'Navigate right',
        '↑  ,  K':            'Navigate up',
        '↓  ,  J':            'Navigate down',
        'Home':                                     'First slide',
        'End':                                      'Last slide',
        'B  ,  .':                          'Pause',
        'F':                                        'Fullscreen',
        'ESC, O':                           'Slide overview'
    };

/**
 * Starts up the presentation if the client is capable.
 */
function initialize( options ) {

    checkCapabilities();

    if( !features.transforms2d && !features.transforms3d ) {
        document.body.setAttribute( 'class', 'no-transforms' );

        // Since JS won't be running any further, we load all lazy
        // loading elements upfront
        var images = toArray( document.getElementsByTagName( 'img' ) ),
            iframes = toArray( document.getElementsByTagName( 'iframe' ) );

        var lazyLoadable = images.concat( iframes );

        for( var i = 0, len = lazyLoadable.length; i < len; i++ ) {
            var element = lazyLoadable[i];
            if( element.getAttribute( 'data-src' ) ) {
                element.setAttribute( 'src', element.getAttribute( 'data-src' ) );
                element.removeAttribute( 'data-src' );
            }
        }

        // If the browser doesn't support core features we won't be
        // using JavaScript to control the presentation
        return;
    }

    // Cache references to key DOM elements
    dom.wrapper = document.querySelector( '.reveal' );
    dom.slides = document.querySelector( '.reveal .slides' );

    // Force a layout when the whole page, incl fonts, has loaded
    window.addEventListener( 'load', layout, false );

    var query = Reveal.getQueryHash();

    // Do not accept new dependencies via query config to avoid
    // the potential of malicious script injection
    if( typeof query['dependencies'] !== 'undefined' ) delete query['dependencies'];

    // Copy options over to our config object
    extend( config, options );
    extend( config, query );

    // Hide the address bar in mobile browsers
    hideAddressBar();

    // Loads the dependencies and continues to #start() once done
    load();

}

/**
 * Inspect the client to see what it's capable of, this
 * should only happens once per runtime.
 */
function checkCapabilities() {

    features.transforms3d = 'WebkitPerspective' in document.body.style ||
        'MozPerspective' in document.body.style ||
        'msPerspective' in document.body.style ||
        'OPerspective' in document.body.style ||
        'perspective' in document.body.style;

    features.transforms2d = 'WebkitTransform' in document.body.style ||
        'MozTransform' in document.body.style ||
        'msTransform' in document.body.style ||
        'OTransform' in document.body.style ||
        'transform' in document.body.style;

    features.requestAnimationFrameMethod = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame;
    features.requestAnimationFrame = typeof features.requestAnimationFrameMethod === 'function';

    features.canvas = !!document.createElement( 'canvas' ).getContext;

    features.touch = !!( 'ontouchstart' in window );

    // Transitions in the overview are disabled in desktop and
    // mobile Safari due to lag
    features.overviewTransitions = !/Version\/[\d\.]+.*Safari/.test( navigator.userAgent );

    isMobileDevice = /(iphone|ipod|ipad|android)/gi.test( navigator.userAgent );

}

/**
 * Loads the dependencies of reveal.js. Dependencies are
 * defined via the configuration option 'dependencies'
 * and will be loaded prior to starting/binding reveal.js.
 * Some dependencies may have an 'async' flag, if so they
 * will load after reveal.js has been started up.
 */
function load() {

    var scripts = [],
        scriptsAsync = [],
        scriptsToPreload = 0;

    // Called once synchronous scripts finish loading
    function proceed() {
        if( scriptsAsync.length ) {
            // Load asynchronous scripts
            head.js.apply( null, scriptsAsync );
        }

        start();
    }

    function loadScript( s ) {
        head.ready( s.src.match( /([\w\d_\-]*)\.?js$|[^\\\/]*$/i )[0], function() {
            // Extension may contain callback functions
            if( typeof s.callback === 'function' ) {
                s.callback.apply( this );
            }

            if( --scriptsToPreload === 0 ) {
                proceed();
            }
        });
    }

    for( var i = 0, len = config.dependencies.length; i < len; i++ ) {
        var s = config.dependencies[i];

        // Load if there's no condition or the condition is truthy
        if( !s.condition || s.condition() ) {
            if( s.async ) {
                scriptsAsync.push( s.src );
            }
            else {
                scripts.push( s.src );
            }

            loadScript( s );
        }
    }

    if( scripts.length ) {
        scriptsToPreload = scripts.length;

        // Load synchronous scripts
        head.js.apply( null, scripts );
    }
    else {
        proceed();
    }

}

/**
 * Starts up reveal.js by binding input events and navigating
 * to the current URL deeplink if there is one.
 */
function start() {

    // Make sure we've got all the DOM elements we need
    setupDOM();

    // Listen to messages posted to this window
    setupPostMessage();

    // Prevent iframes from scrolling the slides out of view
    setupIframeScrollPrevention();

    // Resets all vertical slides so that only the first is visible
    resetVerticalSlides();

    // Updates the presentation to match the current configuration values
    configure();

    // Read the initial hash
    readURL();

    // Update all backgrounds
    updateBackground( true );

    // Notify listeners that the presentation is ready but use a 1ms
    // timeout to ensure it's not fired synchronously after #initialize()
    setTimeout( function() {
        // Enable transitions now that we're loaded
        dom.slides.classList.remove( 'no-transition' );

        loaded = true;

        dispatchEvent( 'ready', {
            'indexh': indexh,
            'indexv': indexv,
            'currentSlide': currentSlide
        } );
    }, 1 );

    // Special setup and config is required when printing to PDF
    if( isPrintingPDF() ) {
        removeEventListeners();

        // The document needs to have loaded for the PDF layout
        // measurements to be accurate
        if( document.readyState === 'complete' ) {
            setupPDF();
        }
        else {
            window.addEventListener( 'load', setupPDF );
        }
    }

}

/**
 * Finds and stores references to DOM elements which are
 * required by the presentation. If a required element is
 * not found, it is created.
 */
function setupDOM() {

    // Prevent transitions while we're loading
    dom.slides.classList.add( 'no-transition' );

    // Background element
    dom.background = createSingletonNode( dom.wrapper, 'div', 'backgrounds', null );

    // Progress bar
    dom.progress = createSingletonNode( dom.wrapper, 'div', 'progress', '<span></span>' );
    dom.progressbar = dom.progress.querySelector( 'span' );

    // Arrow controls
    createSingletonNode( dom.wrapper, 'aside', 'controls',
        '<div class="navigate-left"></div>' +
        '<div class="navigate-right"></div>' +
        '<div class="navigate-up"></div>' +
        '<div class="navigate-down"></div>' );

    // Slide number
    dom.slideNumber = createSingletonNode( dom.wrapper, 'div', 'slide-number', '' );

    // Overlay graphic which is displayed during the paused mode
    createSingletonNode( dom.wrapper, 'div', 'pause-overlay', null );

    // Cache references to elements
    dom.controls = document.querySelector( '.reveal .controls' );
    dom.theme = document.querySelector( '#theme' );

    dom.wrapper.setAttribute( 'role', 'application' );

    // There can be multiple instances of controls throughout the page
    dom.controlsLeft = toArray( document.querySelectorAll( '.navigate-left' ) );
    dom.controlsRight = toArray( document.querySelectorAll( '.navigate-right' ) );
    dom.controlsUp = toArray( document.querySelectorAll( '.navigate-up' ) );
    dom.controlsDown = toArray( document.querySelectorAll( '.navigate-down' ) );
    dom.controlsPrev = toArray( document.querySelectorAll( '.navigate-prev' ) );
    dom.controlsNext = toArray( document.querySelectorAll( '.navigate-next' ) );

    dom.statusDiv = createStatusDiv();
}

/**
 * Creates a hidden div with role aria-live to announce the
 * current slide content. Hide the div off-screen to make it
 * available only to Assistive Technologies.
 */
function createStatusDiv() {

    var statusDiv = document.getElementById( 'aria-status-div' );
    if( !statusDiv ) {
        statusDiv = document.createElement( 'div' );
        statusDiv.style.position = 'absolute';
        statusDiv.style.height = '1px';
        statusDiv.style.width = '1px';
        statusDiv.style.overflow ='hidden';
        statusDiv.style.clip = 'rect( 1px, 1px, 1px, 1px )';
        statusDiv.setAttribute( 'id', 'aria-status-div' );
        statusDiv.setAttribute( 'aria-live', 'polite' );
        statusDiv.setAttribute( 'aria-atomic','true' );
        dom.wrapper.appendChild( statusDiv );
    }
    return statusDiv;

}

/**
 * Configures the presentation for printing to a static
 * PDF.
 */
function setupPDF() {

    var slideSize = getComputedSlideSize( window.innerWidth, window.innerHeight );

    // Dimensions of the PDF pages
    var pageWidth = Math.floor( slideSize.width * ( 1 + config.margin ) ),
        pageHeight = Math.floor( slideSize.height * ( 1 + config.margin  ) );

    // Dimensions of slides within the pages
    var slideWidth = slideSize.width,
        slideHeight = slideSize.height;

    // Let the browser know what page size we want to print
    injectStyleSheet( '@page{size:'+ pageWidth +'px '+ pageHeight +'px; margin: 0;}' );

    // Limit the size of certain elements to the dimensions of the slide
    injectStyleSheet( '.reveal section>img, .reveal section>video, .reveal section>iframe{max-width: '+ slideWidth +'px; max-height:'+ slideHeight +'px}' );

    document.body.classList.add( 'print-pdf' );
    document.body.style.width = pageWidth + 'px';
    document.body.style.height = pageHeight + 'px';

    // Slide and slide background layout
    toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) ).forEach( function( slide ) {

        // Vertical stacks are not centred since their section
        // children will be
        if( slide.classList.contains( 'stack' ) === false ) {
            // Center the slide inside of the page, giving the slide some margin
            var left = ( pageWidth - slideWidth ) / 2,
                top = ( pageHeight - slideHeight ) / 2;

            var contentHeight = getAbsoluteHeight( slide );
            var numberOfPages = Math.max( Math.ceil( contentHeight / pageHeight ), 1 );

            // Center slides vertically
            if( numberOfPages === 1 && config.center || slide.classList.contains( 'center' ) ) {
                top = Math.max( ( pageHeight - contentHeight ) / 2, 0 );
            }

            // Position the slide inside of the page
            slide.style.left = left + 'px';
            slide.style.top = top + 'px';
            slide.style.width = slideWidth + 'px';

            // TODO Backgrounds need to be multiplied when the slide
            // stretches over multiple pages
            var background = slide.querySelector( '.slide-background' );
            if( background ) {
                background.style.width = pageWidth + 'px';
                background.style.height = ( pageHeight * numberOfPages ) + 'px';
                background.style.top = -top + 'px';
                background.style.left = -left + 'px';
            }
        }

    } );

    // Show all fragments
    toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' .fragment' ) ).forEach( function( fragment ) {
        fragment.classList.add( 'visible' );
    } );

}

/**
 * This is an unfortunate necessity. Iframes can trigger the
 * parent window to scroll, for example by focusing an input.
 * This scrolling can not be prevented by hiding overflow in
 * CSS so we have to resort to repeatedly checking if the
 * browser has decided to offset our slides :(
 */
function setupIframeScrollPrevention() {

    if( dom.slides.querySelector( 'iframe' ) ) {
        setInterval( function() {
            if( dom.wrapper.scrollTop !== 0 || dom.wrapper.scrollLeft !== 0 ) {
                dom.wrapper.scrollTop = 0;
                dom.wrapper.scrollLeft = 0;
            }
        }, 500 );
    }

}

/**
 * Creates an HTML element and returns a reference to it.
 * If the element already exists the existing instance will
 * be returned.
 */
function createSingletonNode( container, tagname, classname, innerHTML ) {

    // Find all nodes matching the description
    var nodes = container.querySelectorAll( '.' + classname );

    // Check all matches to find one which is a direct child of
    // the specified container
    for( var i = 0; i < nodes.length; i++ ) {
        var testNode = nodes[i];
        if( testNode.parentNode === container ) {
            return testNode;
        }
    }

    // If no node was found, create it now
    var node = document.createElement( tagname );
    node.classList.add( classname );
    if( typeof innerHTML === 'string' ) {
        node.innerHTML = innerHTML;
    }
    container.appendChild( node );

    return node;

}

/**
 * Creates the slide background elements and appends them
 * to the background container. One element is created per
 * slide no matter if the given slide has visible background.
 */
function createBackgrounds() {

    var printMode = isPrintingPDF();

    // Clear prior backgrounds
    dom.background.innerHTML = '';
    dom.background.classList.add( 'no-transition' );

    // Iterate over all horizontal slides
    toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( slideh ) {

        var backgroundStack;

        if( printMode ) {
            backgroundStack = createBackground( slideh, slideh );
        }
        else {
            backgroundStack = createBackground( slideh, dom.background );
        }

        // Iterate over all vertical slides
        toArray( slideh.querySelectorAll( 'section' ) ).forEach( function( slidev ) {

            if( printMode ) {
                createBackground( slidev, slidev );
            }
            else {
                createBackground( slidev, backgroundStack );
            }

            backgroundStack.classList.add( 'stack' );

        } );

    } );

    // Add parallax background if specified
    if( config.parallaxBackgroundImage ) {

        dom.background.style.backgroundImage = 'url("' + config.parallaxBackgroundImage + '")';
        dom.background.style.backgroundSize = config.parallaxBackgroundSize;

        // Make sure the below properties are set on the element - these properties are
        // needed for proper transitions to be set on the element via CSS. To remove
        // annoying background slide-in effect when the presentation starts, apply
        // these properties after short time delay
        setTimeout( function() {
            dom.wrapper.classList.add( 'has-parallax-background' );
        }, 1 );

    }
    else {

        dom.background.style.backgroundImage = '';
        dom.wrapper.classList.remove( 'has-parallax-background' );

    }

}

/**
 * Creates a background for the given slide.
 *
 * @param {HTMLElement} slide
 * @param {HTMLElement} container The element that the background
 * should be appended to
 */
function createBackground( slide, container ) {

    var data = {
        background: slide.getAttribute( 'data-background' ),
        backgroundSize: slide.getAttribute( 'data-background-size' ),
        backgroundImage: slide.getAttribute( 'data-background-image' ),
        backgroundVideo: slide.getAttribute( 'data-background-video' ),
        backgroundIframe: slide.getAttribute( 'data-background-iframe' ),
        backgroundColor: slide.getAttribute( 'data-background-color' ),
        backgroundRepeat: slide.getAttribute( 'data-background-repeat' ),
        backgroundPosition: slide.getAttribute( 'data-background-position' ),
        backgroundTransition: slide.getAttribute( 'data-background-transition' )
    };

    var element = document.createElement( 'div' );

    // Carry over custom classes from the slide to the background
    element.className = 'slide-background ' + slide.className.replace( /present|past|future/, '' );

    if( data.background ) {
        // Auto-wrap image urls in url(...)
        if( /^(http|file|\/\/)/gi.test( data.background ) || /\.(svg|png|jpg|jpeg|gif|bmp)$/gi.test( data.background ) ) {
            slide.setAttribute( 'data-background-image', data.background );
        }
        else {
            element.style.background = data.background;
        }
    }

    // Create a hash for this combination of background settings.
    // This is used to determine when two slide backgrounds are
    // the same.
    if( data.background || data.backgroundColor || data.backgroundImage || data.backgroundVideo || data.backgroundIframe ) {
        element.setAttribute( 'data-background-hash', data.background +
            data.backgroundSize +
            data.backgroundImage +
            data.backgroundVideo +
            data.backgroundIframe +
            data.backgroundColor +
            data.backgroundRepeat +
            data.backgroundPosition +
            data.backgroundTransition );
    }

    // Additional and optional background properties
    if( data.backgroundSize ) element.style.backgroundSize = data.backgroundSize;
    if( data.backgroundColor ) element.style.backgroundColor = data.backgroundColor;
    if( data.backgroundRepeat ) element.style.backgroundRepeat = data.backgroundRepeat;
    if( data.backgroundPosition ) element.style.backgroundPosition = data.backgroundPosition;
    if( data.backgroundTransition ) element.setAttribute( 'data-background-transition', data.backgroundTransition );

    container.appendChild( element );

    // If backgrounds are being recreated, clear old classes
    slide.classList.remove( 'has-dark-background' );
    slide.classList.remove( 'has-light-background' );

    // If this slide has a background color, add a class that
    // signals if it is light or dark. If the slide has no background
    // color, no class will be set
    var computedBackgroundColor = window.getComputedStyle( element ).backgroundColor;
    if( computedBackgroundColor ) {
        var rgb = colorToRgb( computedBackgroundColor );

        // Ignore fully transparent backgrounds. Some browsers return
        // rgba(0,0,0,0) when reading the computed background color of
        // an element with no background
        if( rgb && rgb.a !== 0 ) {
            if( colorBrightness( computedBackgroundColor ) < 128 ) {
                slide.classList.add( 'has-dark-background' );
            }
            else {
                slide.classList.add( 'has-light-background' );
            }
        }
    }

    return element;

}

/**
 * Registers a listener to postMessage events, this makes it
 * possible to call all reveal.js API methods from another
 * window. For example:
 *
 * revealWindow.postMessage( JSON.stringify({
     *   method: 'slide',
     *   args: [ 2 ]
     * }), '*' );
 */
function setupPostMessage() {

    if( config.postMessage ) {
        window.addEventListener( 'message', function ( event ) {
            var data = event.data;

            // Make sure we're dealing with JSON
            if( typeof data === 'string' && data.charAt( 0 ) === '{' && data.charAt( data.length - 1 ) === '}' ) {
                data = JSON.parse( data );

                // Check if the requested method can be found
                if( data.method && typeof Reveal[data.method] === 'function' ) {
                    Reveal[data.method].apply( Reveal, data.args );
                }
            }
        }, false );
    }

}

/**
 * Applies the configuration settings from the config
 * object. May be called multiple times.
 */
function configure( options ) {

    var numberOfSlides = dom.wrapper.querySelectorAll( SLIDES_SELECTOR ).length;

    dom.wrapper.classList.remove( config.transition );

    // New config options may be passed when this method
    // is invoked through the API after initialization
    if( typeof options === 'object' ) extend( config, options );

    // Force linear transition based on browser capabilities
    if( features.transforms3d === false ) config.transition = 'linear';

    dom.wrapper.classList.add( config.transition );

    dom.wrapper.setAttribute( 'data-transition-speed', config.transitionSpeed );
    dom.wrapper.setAttribute( 'data-background-transition', config.backgroundTransition );

    dom.controls.style.display = config.controls ? 'block' : 'none';
    dom.progress.style.display = config.progress ? 'block' : 'none';

    if( config.rtl ) {
        dom.wrapper.classList.add( 'rtl' );
    }
    else {
        dom.wrapper.classList.remove( 'rtl' );
    }

    if( config.center ) {
        dom.wrapper.classList.add( 'center' );
    }
    else {
        dom.wrapper.classList.remove( 'center' );
    }

    // Exit the paused mode if it was configured off
    if( config.pause === false ) {
        resume();
    }

    if( config.mouseWheel ) {
        document.addEventListener( 'DOMMouseScroll', onDocumentMouseScroll, false ); // FF
        document.addEventListener( 'mousewheel', onDocumentMouseScroll, false );
    }
    else {
        document.removeEventListener( 'DOMMouseScroll', onDocumentMouseScroll, false ); // FF
        document.removeEventListener( 'mousewheel', onDocumentMouseScroll, false );
    }

    // Rolling 3D links
    if( config.rollingLinks ) {
        enableRollingLinks();
    }
    else {
        disableRollingLinks();
    }

    // Iframe link previews
    if( config.previewLinks ) {
        enablePreviewLinks();
    }
    else {
        disablePreviewLinks();
        enablePreviewLinks( '[data-preview-link]' );
    }

    // Remove existing auto-slide controls
    if( autoSlidePlayer ) {
        autoSlidePlayer.destroy();
        autoSlidePlayer = null;
    }

    // Generate auto-slide controls if needed
    if( numberOfSlides > 1 && config.autoSlide && config.autoSlideStoppable && features.canvas && features.requestAnimationFrame ) {
        autoSlidePlayer = new Playback( dom.wrapper, function() {
            return Math.min( Math.max( ( Date.now() - autoSlideStartTime ) / autoSlide, 0 ), 1 );
        } );

        autoSlidePlayer.on( 'click', onAutoSlidePlayerClick );
        autoSlidePaused = false;
    }

    // When fragments are turned off they should be visible
    if( config.fragments === false ) {
        toArray( dom.slides.querySelectorAll( '.fragment' ) ).forEach( function( element ) {
            element.classList.add( 'visible' );
            element.classList.remove( 'current-fragment' );
        } );
    }

    sync();

}

/**
 * Binds all event listeners.
 */
function addEventListeners() {

    eventsAreBound = true;

    window.addEventListener( 'hashchange', onWindowHashChange, false );
    window.addEventListener( 'resize', onWindowResize, false );

    if( config.touch ) {
        dom.wrapper.addEventListener( 'touchstart', onTouchStart, false );
        dom.wrapper.addEventListener( 'touchmove', onTouchMove, false );
        dom.wrapper.addEventListener( 'touchend', onTouchEnd, false );

        // Support pointer-style touch interaction as well
        if( window.navigator.pointerEnabled ) {
            // IE 11 uses un-prefixed version of pointer events
            dom.wrapper.addEventListener( 'pointerdown', onPointerDown, false );
            dom.wrapper.addEventListener( 'pointermove', onPointerMove, false );
            dom.wrapper.addEventListener( 'pointerup', onPointerUp, false );
        }
        else if( window.navigator.msPointerEnabled ) {
            // IE 10 uses prefixed version of pointer events
            dom.wrapper.addEventListener( 'MSPointerDown', onPointerDown, false );
            dom.wrapper.addEventListener( 'MSPointerMove', onPointerMove, false );
            dom.wrapper.addEventListener( 'MSPointerUp', onPointerUp, false );
        }
    }

    if( config.keyboard ) {
        document.addEventListener( 'keydown', onDocumentKeyDown, false );
        document.addEventListener( 'keypress', onDocumentKeyPress, false );
    }

    if( config.progress && dom.progress ) {
        dom.progress.addEventListener( 'click', onProgressClicked, false );
    }

    if( config.focusBodyOnPageVisibilityChange ) {
        var visibilityChange;

        if( 'hidden' in document ) {
            visibilityChange = 'visibilitychange';
        }
        else if( 'msHidden' in document ) {
            visibilityChange = 'msvisibilitychange';
        }
        else if( 'webkitHidden' in document ) {
            visibilityChange = 'webkitvisibilitychange';
        }

        if( visibilityChange ) {
            document.addEventListener( visibilityChange, onPageVisibilityChange, false );
        }
    }

    // Listen to both touch and click events, in case the device
    // supports both
    var pointerEvents = [ 'touchstart', 'click' ];

    // Only support touch for Android, fixes double navigations in
    // stock browser
    if( navigator.userAgent.match( /android/gi ) ) {
        pointerEvents = [ 'touchstart' ];
    }

    pointerEvents.forEach( function( eventName ) {
        dom.controlsLeft.forEach( function( el ) { el.addEventListener( eventName, onNavigateLeftClicked, false ); } );
        dom.controlsRight.forEach( function( el ) { el.addEventListener( eventName, onNavigateRightClicked, false ); } );
        dom.controlsUp.forEach( function( el ) { el.addEventListener( eventName, onNavigateUpClicked, false ); } );
        dom.controlsDown.forEach( function( el ) { el.addEventListener( eventName, onNavigateDownClicked, false ); } );
        dom.controlsPrev.forEach( function( el ) { el.addEventListener( eventName, onNavigatePrevClicked, false ); } );
        dom.controlsNext.forEach( function( el ) { el.addEventListener( eventName, onNavigateNextClicked, false ); } );
    } );

}

/**
 * Unbinds all event listeners.
 */
function removeEventListeners() {

    eventsAreBound = false;

    document.removeEventListener( 'keydown', onDocumentKeyDown, false );
    document.removeEventListener( 'keypress', onDocumentKeyPress, false );
    window.removeEventListener( 'hashchange', onWindowHashChange, false );
    window.removeEventListener( 'resize', onWindowResize, false );

    dom.wrapper.removeEventListener( 'touchstart', onTouchStart, false );
    dom.wrapper.removeEventListener( 'touchmove', onTouchMove, false );
    dom.wrapper.removeEventListener( 'touchend', onTouchEnd, false );

    // IE11
    if( window.navigator.pointerEnabled ) {
        dom.wrapper.removeEventListener( 'pointerdown', onPointerDown, false );
        dom.wrapper.removeEventListener( 'pointermove', onPointerMove, false );
        dom.wrapper.removeEventListener( 'pointerup', onPointerUp, false );
    }
    // IE10
    else if( window.navigator.msPointerEnabled ) {
        dom.wrapper.removeEventListener( 'MSPointerDown', onPointerDown, false );
        dom.wrapper.removeEventListener( 'MSPointerMove', onPointerMove, false );
        dom.wrapper.removeEventListener( 'MSPointerUp', onPointerUp, false );
    }

    if ( config.progress && dom.progress ) {
        dom.progress.removeEventListener( 'click', onProgressClicked, false );
    }

    [ 'touchstart', 'click' ].forEach( function( eventName ) {
        dom.controlsLeft.forEach( function( el ) { el.removeEventListener( eventName, onNavigateLeftClicked, false ); } );
        dom.controlsRight.forEach( function( el ) { el.removeEventListener( eventName, onNavigateRightClicked, false ); } );
        dom.controlsUp.forEach( function( el ) { el.removeEventListener( eventName, onNavigateUpClicked, false ); } );
        dom.controlsDown.forEach( function( el ) { el.removeEventListener( eventName, onNavigateDownClicked, false ); } );
        dom.controlsPrev.forEach( function( el ) { el.removeEventListener( eventName, onNavigatePrevClicked, false ); } );
        dom.controlsNext.forEach( function( el ) { el.removeEventListener( eventName, onNavigateNextClicked, false ); } );
    } );

}

/**
 * Extend object a with the properties of object b.
 * If there's a conflict, object b takes precedence.
 */
function extend( a, b ) {

    for( var i in b ) {
        a[ i ] = b[ i ];
    }

}

/**
 * Converts the target object to an array.
 */
function toArray( o ) {

    return Array.prototype.slice.call( o );

}

/**
 * Utility for deserializing a value.
 */
function deserialize( value ) {

    if( typeof value === 'string' ) {
        if( value === 'null' ) return null;
        else if( value === 'true' ) return true;
        else if( value === 'false' ) return false;
        else if( value.match( /^\d+$/ ) ) return parseFloat( value );
    }

    return value;

}

/**
 * Measures the distance in pixels between point a
 * and point b.
 *
 * @param {Object} a point with x/y properties
 * @param {Object} b point with x/y properties
 */
function distanceBetween( a, b ) {

    var dx = a.x - b.x,
        dy = a.y - b.y;

    return Math.sqrt( dx*dx + dy*dy );

}

/**
 * Applies a CSS transform to the target element.
 */
function transformElement( element, transform ) {

    element.style.WebkitTransform = transform;
    element.style.MozTransform = transform;
    element.style.msTransform = transform;
    element.style.transform = transform;

}

/**
 * Applies CSS transforms to the slides container. The container
 * is transformed from two separate sources: layout and the overview
 * mode.
 */
function transformSlides( transforms ) {

    // Pick up new transforms from arguments
    if( typeof transforms.layout === 'string' ) slidesTransform.layout = transforms.layout;
    if( typeof transforms.overview === 'string' ) slidesTransform.overview = transforms.overview;

    // Apply the transforms to the slides container
    if( slidesTransform.layout ) {
        transformElement( dom.slides, slidesTransform.layout + ' ' + slidesTransform.overview );
    }
    else {
        transformElement( dom.slides, slidesTransform.overview );
    }

}

/**
 * Injects the given CSS styles into the DOM.
 */
function injectStyleSheet( value ) {

    var tag = document.createElement( 'style' );
    tag.type = 'text/css';
    if( tag.styleSheet ) {
        tag.styleSheet.cssText = value;
    }
    else {
        tag.appendChild( document.createTextNode( value ) );
    }
    document.getElementsByTagName( 'head' )[0].appendChild( tag );

}

/**
 * Converts various color input formats to an {r:0,g:0,b:0} object.
 *
 * @param {String} color The string representation of a color,
 * the following formats are supported:
 * - #000
 * - #000000
 * - rgb(0,0,0)
 */
function colorToRgb( color ) {

    var hex3 = color.match( /^#([0-9a-f]{3})$/i );
    if( hex3 && hex3[1] ) {
        hex3 = hex3[1];
        return {
            r: parseInt( hex3.charAt( 0 ), 16 ) * 0x11,
            g: parseInt( hex3.charAt( 1 ), 16 ) * 0x11,
            b: parseInt( hex3.charAt( 2 ), 16 ) * 0x11
        };
    }

    var hex6 = color.match( /^#([0-9a-f]{6})$/i );
    if( hex6 && hex6[1] ) {
        hex6 = hex6[1];
        return {
            r: parseInt( hex6.substr( 0, 2 ), 16 ),
            g: parseInt( hex6.substr( 2, 2 ), 16 ),
            b: parseInt( hex6.substr( 4, 2 ), 16 )
        };
    }

    var rgb = color.match( /^rgb\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)$/i );
    if( rgb ) {
        return {
            r: parseInt( rgb[1], 10 ),
            g: parseInt( rgb[2], 10 ),
            b: parseInt( rgb[3], 10 )
        };
    }

    var rgba = color.match( /^rgba\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\,\s*([\d]+|[\d]*.[\d]+)\s*\)$/i );
    if( rgba ) {
        return {
            r: parseInt( rgba[1], 10 ),
            g: parseInt( rgba[2], 10 ),
            b: parseInt( rgba[3], 10 ),
            a: parseFloat( rgba[4] )
        };
    }

    return null;

}

/**
 * Calculates brightness on a scale of 0-255.
 *
 * @param color See colorStringToRgb for supported formats.
 */
function colorBrightness( color ) {

    if( typeof color === 'string' ) color = colorToRgb( color );

    if( color ) {
        return ( color.r * 299 + color.g * 587 + color.b * 114 ) / 1000;
    }

    return null;

}

/**
 * Retrieves the height of the given element by looking
 * at the position and height of its immediate children.
 */
function getAbsoluteHeight( element ) {

    var height = 0;

    if( element ) {
        var absoluteChildren = 0;

        toArray( element.childNodes ).forEach( function( child ) {

            if( typeof child.offsetTop === 'number' && child.style ) {
                // Count # of abs children
                if( window.getComputedStyle( child ).position === 'absolute' ) {
                    absoluteChildren += 1;
                }

                height = Math.max( height, child.offsetTop + child.offsetHeight );
            }

        } );

        // If there are no absolute children, use offsetHeight
        if( absoluteChildren === 0 ) {
            height = element.offsetHeight;
        }

    }

    return height;

}

/**
 * Returns the remaining height within the parent of the
 * target element.
 *
 * remaining height = [ configured parent height ] - [ current parent height ]
 */
function getRemainingHeight( element, height ) {

    height = height || 0;

    if( element ) {
        var newHeight, oldHeight = element.style.height;

        // Change the .stretch element height to 0 in order find the height of all
        // the other elements
        element.style.height = '0px';
        newHeight = height - element.parentNode.offsetHeight;

        // Restore the old height, just in case
        element.style.height = oldHeight + 'px';

        return newHeight;
    }

    return height;

}

/**
 * Checks if this instance is being used to print a PDF.
 */
function isPrintingPDF() {

    return ( /print-pdf/gi ).test( window.location.search );

}

/**
 * Hides the address bar if we're on a mobile device.
 */
function hideAddressBar() {

    if( config.hideAddressBar && isMobileDevice ) {
        // Events that should trigger the address bar to hide
        window.addEventListener( 'load', removeAddressBar, false );
        window.addEventListener( 'orientationchange', removeAddressBar, false );
    }

}

/**
 * Causes the address bar to hide on mobile devices,
 * more vertical space ftw.
 */
function removeAddressBar() {

    setTimeout( function() {
        window.scrollTo( 0, 1 );
    }, 10 );

}

/**
 * Dispatches an event of the specified type from the
 * reveal DOM element.
 */
function dispatchEvent( type, args ) {

    var event = document.createEvent( 'HTMLEvents', 1, 2 );
    event.initEvent( type, true, true );
    extend( event, args );
    dom.wrapper.dispatchEvent( event );

    // If we're in an iframe, post each reveal.js event to the
    // parent window. Used by the notes plugin
    if( config.postMessageEvents && window.parent !== window.self ) {
        window.parent.postMessage( JSON.stringify({ namespace: 'reveal', eventName: type, state: getState() }), '*' );
    }

}

/**
 * Wrap all links in 3D goodness.
 */
function enableRollingLinks() {

    if( features.transforms3d && !( 'msPerspective' in document.body.style ) ) {
        var anchors = dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' a' );

        for( var i = 0, len = anchors.length; i < len; i++ ) {
            var anchor = anchors[i];

            if( anchor.textContent && !anchor.querySelector( '*' ) && ( !anchor.className || !anchor.classList.contains( anchor, 'roll' ) ) ) {
                var span = document.createElement('span');
                span.setAttribute('data-title', anchor.text);
                span.innerHTML = anchor.innerHTML;

                anchor.classList.add( 'roll' );
                anchor.innerHTML = '';
                anchor.appendChild(span);
            }
        }
    }

}

/**
 * Unwrap all 3D links.
 */
function disableRollingLinks() {

    var anchors = dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' a.roll' );

    for( var i = 0, len = anchors.length; i < len; i++ ) {
        var anchor = anchors[i];
        var span = anchor.querySelector( 'span' );

        if( span ) {
            anchor.classList.remove( 'roll' );
            anchor.innerHTML = span.innerHTML;
        }
    }

}

/**
 * Bind preview frame links.
 */
function enablePreviewLinks( selector ) {

    var anchors = toArray( document.querySelectorAll( selector ? selector : 'a' ) );

    anchors.forEach( function( element ) {
        if( /^(http|www)/gi.test( element.getAttribute( 'href' ) ) ) {
            element.addEventListener( 'click', onPreviewLinkClicked, false );
        }
    } );

}

/**
 * Unbind preview frame links.
 */
function disablePreviewLinks() {

    var anchors = toArray( document.querySelectorAll( 'a' ) );

    anchors.forEach( function( element ) {
        if( /^(http|www)/gi.test( element.getAttribute( 'href' ) ) ) {
            element.removeEventListener( 'click', onPreviewLinkClicked, false );
        }
    } );

}

/**
 * Opens a preview window for the target URL.
 */
function showPreview( url ) {

    closeOverlay();

    dom.overlay = document.createElement( 'div' );
    dom.overlay.classList.add( 'overlay' );
    dom.overlay.classList.add( 'overlay-preview' );
    dom.wrapper.appendChild( dom.overlay );

    dom.overlay.innerHTML = [
        '<header>',
        '<a class="close" href="#"><span class="icon"></span></a>',
        '<a class="external" href="'+ url +'" target="_blank"><span class="icon"></span></a>',
        '</header>',
        '<div class="spinner"></div>',
        '<div class="viewport">',
        '<iframe src="'+ url +'"></iframe>',
        '</div>'
    ].join('');

    dom.overlay.querySelector( 'iframe' ).addEventListener( 'load', function( event ) {
        dom.overlay.classList.add( 'loaded' );
    }, false );

    dom.overlay.querySelector( '.close' ).addEventListener( 'click', function( event ) {
        closeOverlay();
        event.preventDefault();
    }, false );

    dom.overlay.querySelector( '.external' ).addEventListener( 'click', function( event ) {
        closeOverlay();
    }, false );

    setTimeout( function() {
        dom.overlay.classList.add( 'visible' );
    }, 1 );

}

/**
 * Opens a overlay window with help material.
 */
function showHelp() {

    if( config.help ) {

        closeOverlay();

        dom.overlay = document.createElement( 'div' );
        dom.overlay.classList.add( 'overlay' );
        dom.overlay.classList.add( 'overlay-help' );
        dom.wrapper.appendChild( dom.overlay );

        var html = '<p class="title">Keyboard Shortcuts</p><br/>';

        html += '<table><th>KEY</th><th>ACTION</th>';
        for( var key in keyboardShortcuts ) {
            html += '<tr><td>' + key + '</td><td>' + keyboardShortcuts[ key ] + '</td></tr>';
        }

        html += '</table>';

        dom.overlay.innerHTML = [
            '<header>',
            '<a class="close" href="#"><span class="icon"></span></a>',
            '</header>',
            '<div class="viewport">',
            '<div class="viewport-inner">'+ html +'</div>',
            '</div>'
        ].join('');

        dom.overlay.querySelector( '.close' ).addEventListener( 'click', function( event ) {
            closeOverlay();
            event.preventDefault();
        }, false );

        setTimeout( function() {
            dom.overlay.classList.add( 'visible' );
        }, 1 );

    }

}

/**
 * Closes any currently open overlay.
 */
function closeOverlay() {

    if( dom.overlay ) {
        dom.overlay.parentNode.removeChild( dom.overlay );
        dom.overlay = null;
    }

}

/**
 * Applies JavaScript-controlled layout rules to the
 * presentation.
 */
function layout() {

    if( dom.wrapper && !isPrintingPDF() ) {

        var size = getComputedSlideSize();

        var slidePadding = 20; // TODO Dig this out of DOM

        // Layout the contents of the slides
        layoutSlideContents( config.width, config.height, slidePadding );

        dom.slides.style.width = size.width + 'px';
        dom.slides.style.height = size.height + 'px';

        // Determine scale of content to fit within available space
        scale = Math.min( size.presentationWidth / size.width, size.presentationHeight / size.height );

        // Respect max/min scale settings
        scale = Math.max( scale, config.minScale );
        scale = Math.min( scale, config.maxScale );

        // Don't apply any scaling styles if scale is 1
        if( scale === 1 ) {
            dom.slides.style.zoom = '';
            dom.slides.style.left = '';
            dom.slides.style.top = '';
            dom.slides.style.bottom = '';
            dom.slides.style.right = '';
            transformSlides( { layout: '' } );
        }
        else {
            // Prefer zooming in desktop Chrome so that content remains crisp
            if( !isMobileDevice && /chrome/i.test( navigator.userAgent ) && typeof dom.slides.style.zoom !== 'undefined' ) {
                dom.slides.style.zoom = scale;
                dom.slides.style.marginTop = config.marginTop;
                dom.slides.style.marginLeft = config.marginLeft;
                transformSlides( { layout: '' } );
            }
            // Apply scale transform as a fallback
            else {
                // dom.slides.style.left = '50%';
                // dom.slides.style.top = '44%';
                // dom.slides.style.bottom = 'auto';
                // dom.slides.style.right = 'auto';
                dom.slides.style.marginTop = config.marginTop;
                dom.slides.style.marginLeft = config.marginLeft;
                dom.slides.style.marginBottom = 'auto';
                dom.slides.style.marginRight = 'auto';
                transformSlides( { layout: 'translate(-50%, -50%) scale('+ scale +') translate(50%, 50%)' } );
            }
        }

        // Select all slides, vertical and horizontal
        var slides = toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) );

        for( var i = 0, len = slides.length; i < len; i++ ) {
            var slide = slides[ i ];

            // Don't bother updating invisible slides
            if( slide.style.display === 'none' ) {
                continue;
            }

            if( config.center || slide.classList.contains( 'center' ) ) {
                // Vertical stacks are not centred since their section
                // children will be
                if( slide.classList.contains( 'stack' ) ) {
                    slide.style.top = 0;
                }
                else {
                    slide.style.top = Math.max( ( ( size.height - getAbsoluteHeight( slide ) ) / 2 ) - slidePadding, 0 ) + 'px';
                }
            }
            else {
                slide.style.top = '';
            }

        }

        updateProgress();
        updateParallax();

    }

}

/**
 * Applies layout logic to the contents of all slides in
 * the presentation.
 */
function layoutSlideContents( width, height, padding ) {

    // Handle sizing of elements with the 'stretch' class
    toArray( dom.slides.querySelectorAll( 'section > .stretch' ) ).forEach( function( element ) {

        // Determine how much vertical space we can use
        var remainingHeight = getRemainingHeight( element, height );

        // Consider the aspect ratio of media elements
        if( /(img|video)/gi.test( element.nodeName ) ) {
            var nw = element.naturalWidth || element.videoWidth,
                nh = element.naturalHeight || element.videoHeight;

            var es = Math.min( width / nw, remainingHeight / nh );

            element.style.width = ( nw * es ) + 'px';
            element.style.height = ( nh * es ) + 'px';

        }
        else {
            element.style.width = width + 'px';
            element.style.height = remainingHeight + 'px';
        }

    } );

}

/**
 * Calculates the computed pixel size of our slides. These
 * values are based on the width and height configuration
 * options.
 */
function getComputedSlideSize( presentationWidth, presentationHeight ) {

    var size = {
        // Slide size
        width: config.width,
        height: config.height,

        // Presentation size
        presentationWidth: presentationWidth || dom.wrapper.offsetWidth,
        presentationHeight: presentationHeight || dom.wrapper.offsetHeight
    };

    // Reduce available space by margin
    size.presentationWidth -= ( size.presentationWidth * config.margin );
    size.presentationHeight -= ( size.presentationHeight * config.margin );

    // Slide width may be a percentage of available width
    if( typeof size.width === 'string' && /%$/.test( size.width ) ) {
        size.width = parseInt( size.width, 10 ) / 100 * size.presentationWidth;
    }

    // Slide height may be a percentage of available height
    if( typeof size.height === 'string' && /%$/.test( size.height ) ) {
        size.height = parseInt( size.height, 10 ) / 100 * size.presentationHeight;
    }

    return size;

}

/**
 * Stores the vertical index of a stack so that the same
 * vertical slide can be selected when navigating to and
 * from the stack.
 *
 * @param {HTMLElement} stack The vertical stack element
 * @param {int} v Index to memorize
 */
function setPreviousVerticalIndex( stack, v ) {

    if( typeof stack === 'object' && typeof stack.setAttribute === 'function' ) {
        stack.setAttribute( 'data-previous-indexv', v || 0 );
    }

}

/**
 * Retrieves the vertical index which was stored using
 * #setPreviousVerticalIndex() or 0 if no previous index
 * exists.
 *
 * @param {HTMLElement} stack The vertical stack element
 */
function getPreviousVerticalIndex( stack ) {

    if( typeof stack === 'object' && typeof stack.setAttribute === 'function' && stack.classList.contains( 'stack' ) ) {
        // Prefer manually defined start-indexv
        var attributeName = stack.hasAttribute( 'data-start-indexv' ) ? 'data-start-indexv' : 'data-previous-indexv';

        return parseInt( stack.getAttribute( attributeName ) || 0, 10 );
    }

    return 0;

}

/**
 * Displays the overview of slides (quick nav) by scaling
 * down and arranging all slide elements.
 */
function activateOverview() {

    // Only proceed if enabled in config
    if( config.overview && !isOverview() ) {

        overview = true;

        dom.wrapper.classList.add( 'overview' );
        dom.wrapper.classList.remove( 'overview-deactivating' );

        if( features.overviewTransitions ) {
            setTimeout( function() {
                dom.wrapper.classList.add( 'overview-animated' );
            }, 1 );
        }

        // Don't auto-slide while in overview mode
        cancelAutoSlide();

        // Move the backgrounds element into the slide container to
        // that the same scaling is applied
        dom.slides.appendChild( dom.background );

        // Clicking on an overview slide navigates to it
        toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) ).forEach( function( slide ) {
            if( !slide.classList.contains( 'stack' ) ) {
                slide.addEventListener( 'click', onOverviewSlideClicked, true );
            }
        } );

        updateSlidesVisibility();
        layoutOverview();
        updateOverview();

        layout();

        // Notify observers of the overview showing
        dispatchEvent( 'overviewshown', {
            'indexh': indexh,
            'indexv': indexv,
            'currentSlide': currentSlide
        } );

    }

}

/**
 * Uses CSS transforms to position all slides in a grid for
 * display inside of the overview mode.
 */
function layoutOverview() {

    var margin = 70;
    var slideWidth = config.width + margin,
        slideHeight = config.height + margin;

    // Reverse in RTL mode
    if( config.rtl ) {
        slideWidth = -slideWidth;
    }

    // Layout slides
    toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( hslide, h ) {
        hslide.setAttribute( 'data-index-h', h );
        transformElement( hslide, 'translate3d(' + ( h * slideWidth ) + 'px, 0, 0)' );

        if( hslide.classList.contains( 'stack' ) ) {

            toArray( hslide.querySelectorAll( 'section' ) ).forEach( function( vslide, v ) {
                vslide.setAttribute( 'data-index-h', h );
                vslide.setAttribute( 'data-index-v', v );

                transformElement( vslide, 'translate3d(0, ' + ( v * slideHeight ) + 'px, 0)' );
            } );

        }
    } );

    // Layout slide backgrounds
    toArray( dom.background.childNodes ).forEach( function( hbackground, h ) {
        transformElement( hbackground, 'translate3d(' + ( h * slideWidth ) + 'px, 0, 0)' );

        toArray( hbackground.querySelectorAll( '.slide-background' ) ).forEach( function( vbackground, v ) {
            transformElement( vbackground, 'translate3d(0, ' + ( v * slideHeight ) + 'px, 0)' );
        } );
    } );

}

/**
 * Moves the overview viewport to the current slides.
 * Called each time the current slide changes.
 */
function updateOverview() {

    var margin = 70;
    var slideWidth = config.width + margin,
        slideHeight = config.height + margin;

    // Reverse in RTL mode
    if( config.rtl ) {
        slideWidth = -slideWidth;
    }

    transformSlides( {
        overview: [
            'translateX('+ ( -indexh * slideWidth ) +'px)',
            'translateY('+ ( -indexv * slideHeight ) +'px)',
            'translateZ('+ ( window.innerWidth < 400 ? -1000 : -2500 ) +'px)'
        ].join( ' ' )
    } );

}

/**
 * Exits the slide overview and enters the currently
 * active slide.
 */
function deactivateOverview() {

    // Only proceed if enabled in config
    if( config.overview ) {

        overview = false;

        dom.wrapper.classList.remove( 'overview' );
        dom.wrapper.classList.remove( 'overview-animated' );

        // Temporarily add a class so that transitions can do different things
        // depending on whether they are exiting/entering overview, or just
        // moving from slide to slide
        dom.wrapper.classList.add( 'overview-deactivating' );

        setTimeout( function () {
            dom.wrapper.classList.remove( 'overview-deactivating' );
        }, 1 );

        // Move the background element back out
        dom.wrapper.appendChild( dom.background );

        // Clean up changes made to slides
        toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) ).forEach( function( slide ) {
            transformElement( slide, '' );

            slide.removeEventListener( 'click', onOverviewSlideClicked, true );
        } );

        // Clean up changes made to backgrounds
        toArray( dom.background.querySelectorAll( '.slide-background' ) ).forEach( function( background ) {
            transformElement( background, '' );
        } );

        transformSlides( { overview: '' } );

        slide( indexh, indexv );

        layout();

        cueAutoSlide();

        // Notify observers of the overview hiding
        dispatchEvent( 'overviewhidden', {
            'indexh': indexh,
            'indexv': indexv,
            'currentSlide': currentSlide
        } );

    }
}

/**
 * Toggles the slide overview mode on and off.
 *
 * @param {Boolean} override Optional flag which overrides the
 * toggle logic and forcibly sets the desired state. True means
 * overview is open, false means it's closed.
 */
function toggleOverview( override ) {

    if( typeof override === 'boolean' ) {
        override ? activateOverview() : deactivateOverview();
    }
    else {
        isOverview() ? deactivateOverview() : activateOverview();
    }

}

/**
 * Checks if the overview is currently active.
 *
 * @return {Boolean} true if the overview is active,
 * false otherwise
 */
function isOverview() {

    return overview;

}

/**
 * Checks if the current or specified slide is vertical
 * (nested within another slide).
 *
 * @param {HTMLElement} slide [optional] The slide to check
 * orientation of
 */
function isVerticalSlide( slide ) {

    // Prefer slide argument, otherwise use current slide
    slide = slide ? slide : currentSlide;

    return slide && slide.parentNode && !!slide.parentNode.nodeName.match( /section/i );

}

/**
 * Handling the fullscreen functionality via the fullscreen API
 *
 * @see http://fullscreen.spec.whatwg.org/
 * @see https://developer.mozilla.org/en-US/docs/DOM/Using_fullscreen_mode
 */
function enterFullscreen() {

    var element = document.body;

    // Check which implementation is available
    var requestMethod = element.requestFullScreen ||
        element.webkitRequestFullscreen ||
        element.webkitRequestFullScreen ||
        element.mozRequestFullScreen ||
        element.msRequestFullscreen;

    if( requestMethod ) {
        requestMethod.apply( element );
    }

}

/**
 * Enters the paused mode which fades everything on screen to
 * black.
 */
function pause() {

    if( config.pause ) {
        var wasPaused = dom.wrapper.classList.contains( 'paused' );

        cancelAutoSlide();
        dom.wrapper.classList.add( 'paused' );

        if( wasPaused === false ) {
            dispatchEvent( 'paused' );
        }
    }

}

/**
 * Exits from the paused mode.
 */
function resume() {

    var wasPaused = dom.wrapper.classList.contains( 'paused' );
    dom.wrapper.classList.remove( 'paused' );

    cueAutoSlide();

    if( wasPaused ) {
        dispatchEvent( 'resumed' );
    }

}

/**
 * Toggles the paused mode on and off.
 */
function togglePause( override ) {

    if( typeof override === 'boolean' ) {
        override ? pause() : resume();
    }
    else {
        isPaused() ? resume() : pause();
    }

}

/**
 * Checks if we are currently in the paused mode.
 */
function isPaused() {

    return dom.wrapper.classList.contains( 'paused' );

}

/**
 * Toggles the auto slide mode on and off.
 *
 * @param {Boolean} override Optional flag which sets the desired state.
 * True means autoplay starts, false means it stops.
 */

function toggleAutoSlide( override ) {

    if( typeof override === 'boolean' ) {
        override ? resumeAutoSlide() : pauseAutoSlide();
    }

    else {
        autoSlidePaused ? resumeAutoSlide() : pauseAutoSlide();
    }

}

/**
 * Checks if the auto slide mode is currently on.
 */
function isAutoSliding() {

    return !!( autoSlide && !autoSlidePaused );

}

/**
 * Steps from the current point in the presentation to the
 * slide which matches the specified horizontal and vertical
 * indices.
 *
 * @param {int} h Horizontal index of the target slide
 * @param {int} v Vertical index of the target slide
 * @param {int} f Optional index of a fragment within the
 * target slide to activate
 * @param {int} o Optional origin for use in multimaster environments
 */
function slide( h, v, f, o ) {

    // Remember where we were at before
    previousSlide = currentSlide;

    // Query all horizontal slides in the deck
    var horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR );

    // If no vertical index is specified and the upcoming slide is a
    // stack, resume at its previous vertical index
    if( v === undefined && !isOverview() ) {
        v = getPreviousVerticalIndex( horizontalSlides[ h ] );
    }

    // If we were on a vertical stack, remember what vertical index
    // it was on so we can resume at the same position when returning
    if( previousSlide && previousSlide.parentNode && previousSlide.parentNode.classList.contains( 'stack' ) ) {
        setPreviousVerticalIndex( previousSlide.parentNode, indexv );
    }

    // Remember the state before this slide
    var stateBefore = state.concat();

    // Reset the state array
    state.length = 0;

    var indexhBefore = indexh || 0,
        indexvBefore = indexv || 0;

    // Activate and transition to the new slide
    indexh = updateSlides( HORIZONTAL_SLIDES_SELECTOR, h === undefined ? indexh : h );
    indexv = updateSlides( VERTICAL_SLIDES_SELECTOR, v === undefined ? indexv : v );

    // Update the visibility of slides now that the indices have changed
    updateSlidesVisibility();

    layout();

    // Apply the new state
    stateLoop: for( var i = 0, len = state.length; i < len; i++ ) {
        // Check if this state existed on the previous slide. If it
        // did, we will avoid adding it repeatedly
        for( var j = 0; j < stateBefore.length; j++ ) {
            if( stateBefore[j] === state[i] ) {
                stateBefore.splice( j, 1 );
                continue stateLoop;
            }
        }

        document.documentElement.classList.add( state[i] );

        // Dispatch custom event matching the state's name
        dispatchEvent( state[i] );
    }

    // Clean up the remains of the previous state
    while( stateBefore.length ) {
        document.documentElement.classList.remove( stateBefore.pop() );
    }

    // Update the overview if it's currently active
    if( isOverview() ) {
        updateOverview();
    }

    // Find the current horizontal slide and any possible vertical slides
    // within it
    var currentHorizontalSlide = horizontalSlides[ indexh ],
        currentVerticalSlides = currentHorizontalSlide.querySelectorAll( 'section' );

    // Store references to the previous and current slides
    currentSlide = currentVerticalSlides[ indexv ] || currentHorizontalSlide;

    // Show fragment, if specified
    if( typeof f !== 'undefined' ) {
        navigateFragment( f );
    }

    // Dispatch an event if the slide changed
    var slideChanged = ( indexh !== indexhBefore || indexv !== indexvBefore );
    if( slideChanged ) {
        dispatchEvent( 'slidechanged', {
            'indexh': indexh,
            'indexv': indexv,
            'previousSlide': previousSlide,
            'currentSlide': currentSlide,
            'origin': o
        } );
    }
    else {
        // Ensure that the previous slide is never the same as the current
        previousSlide = null;
    }

    // Solves an edge case where the previous slide maintains the
    // 'present' class when navigating between adjacent vertical
    // stacks
    if( previousSlide ) {
        previousSlide.classList.remove( 'present' );
        previousSlide.setAttribute( 'aria-hidden', 'true' );

        // Reset all slides upon navigate to home
        // Issue: #285
        if ( dom.wrapper.querySelector( HOME_SLIDE_SELECTOR ).classList.contains( 'present' ) ) {
            // Launch async task
            setTimeout( function () {
                var slides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.stack') ), i;
                for( i in slides ) {
                    if( slides[i] ) {
                        // Reset stack
                        setPreviousVerticalIndex( slides[i], 0 );
                    }
                }
            }, 0 );
        }
    }

    // Handle embedded content
    if( slideChanged || !previousSlide ) {
        stopEmbeddedContent( previousSlide );
        startEmbeddedContent( currentSlide );
    }

    // Announce the current slide contents, for screen readers
    dom.statusDiv.textContent = currentSlide.textContent;

    updateControls();
    updateProgress();
    updateBackground();
    updateParallax();
    updateSlideNumber();

    // Update the URL hash
    writeURL();

    cueAutoSlide();

}

/**
 * Syncs the presentation with the current DOM. Useful
 * when new slides or control elements are added or when
 * the configuration has changed.
 */
function sync() {

    // Subscribe to input
    removeEventListeners();
    addEventListeners();

    // Force a layout to make sure the current config is accounted for
    layout();

    // Reflect the current autoSlide value
    autoSlide = config.autoSlide;

    // Start auto-sliding if it's enabled
    cueAutoSlide();

    // Re-create the slide backgrounds
    createBackgrounds();

    // Write the current hash to the URL
    writeURL();

    sortAllFragments();

    updateControls();
    updateProgress();
    updateBackground( true );
    updateSlideNumber();
    updateSlidesVisibility();

    formatEmbeddedContent();
    startEmbeddedContent( currentSlide );

    if( isOverview() ) {
        layoutOverview();
    }

}

/**
 * Resets all vertical slides so that only the first
 * is visible.
 */
function resetVerticalSlides() {

    var horizontalSlides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
    horizontalSlides.forEach( function( horizontalSlide ) {

        var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) );
        verticalSlides.forEach( function( verticalSlide, y ) {

            if( y > 0 ) {
                verticalSlide.classList.remove( 'present' );
                verticalSlide.classList.remove( 'past' );
                verticalSlide.classList.add( 'future' );
                verticalSlide.setAttribute( 'aria-hidden', 'true' );
            }

        } );

    } );

}

/**
 * Sorts and formats all of fragments in the
 * presentation.
 */
function sortAllFragments() {

    var horizontalSlides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
    horizontalSlides.forEach( function( horizontalSlide ) {

        var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) );
        verticalSlides.forEach( function( verticalSlide, y ) {

            sortFragments( verticalSlide.querySelectorAll( '.fragment' ) );

        } );

        if( verticalSlides.length === 0 ) sortFragments( horizontalSlide.querySelectorAll( '.fragment' ) );

    } );

}

/**
 * Updates one dimension of slides by showing the slide
 * with the specified index.
 *
 * @param {String} selector A CSS selector that will fetch
 * the group of slides we are working with
 * @param {Number} index The index of the slide that should be
 * shown
 *
 * @return {Number} The index of the slide that is now shown,
 * might differ from the passed in index if it was out of
 * bounds.
 */
function updateSlides( selector, index ) {

    // Select all slides and convert the NodeList result to
    // an array
    var slides = toArray( dom.wrapper.querySelectorAll( selector ) ),
        slidesLength = slides.length;

    var printMode = isPrintingPDF();

    if( slidesLength ) {

        // Should the index loop?
        if( config.loop ) {
            index %= slidesLength;

            if( index < 0 ) {
                index = slidesLength + index;
            }
        }

        // Enforce max and minimum index bounds
        index = Math.max( Math.min( index, slidesLength - 1 ), 0 );

        for( var i = 0; i < slidesLength; i++ ) {
            var element = slides[i];

            var reverse = config.rtl && !isVerticalSlide( element );

            element.classList.remove( 'past' );
            element.classList.remove( 'present' );
            element.classList.remove( 'future' );

            // http://www.w3.org/html/wg/drafts/html/master/editing.html#the-hidden-attribute
            element.setAttribute( 'hidden', '' );
            element.setAttribute( 'aria-hidden', 'true' );

            // If this element contains vertical slides
            if( element.querySelector( 'section' ) ) {
                element.classList.add( 'stack' );
            }

            // If we're printing static slides, all slides are "present"
            if( printMode ) {
                element.classList.add( 'present' );
                continue;
            }

            if( i < index ) {
                // Any element previous to index is given the 'past' class
                element.classList.add( reverse ? 'future' : 'past' );

                if( config.fragments ) {
                    var pastFragments = toArray( element.querySelectorAll( '.fragment' ) );

                    // Show all fragments on prior slides
                    while( pastFragments.length ) {
                        var pastFragment = pastFragments.pop();
                        pastFragment.classList.add( 'visible' );
                        pastFragment.classList.remove( 'current-fragment' );
                    }
                }
            }
            else if( i > index ) {
                // Any element subsequent to index is given the 'future' class
                element.classList.add( reverse ? 'past' : 'future' );

                if( config.fragments ) {
                    var futureFragments = toArray( element.querySelectorAll( '.fragment.visible' ) );

                    // No fragments in future slides should be visible ahead of time
                    while( futureFragments.length ) {
                        var futureFragment = futureFragments.pop();
                        futureFragment.classList.remove( 'visible' );
                        futureFragment.classList.remove( 'current-fragment' );
                    }
                }
            }
        }

        // Mark the current slide as present
        slides[index].classList.add( 'present' );
        slides[index].removeAttribute( 'hidden' );
        slides[index].removeAttribute( 'aria-hidden' );

        // If this slide has a state associated with it, add it
        // onto the current state of the deck
        var slideState = slides[index].getAttribute( 'data-state' );
        if( slideState ) {
            state = state.concat( slideState.split( ' ' ) );
        }

    }
    else {
        // Since there are no slides we can't be anywhere beyond the
        // zeroth index
        index = 0;
    }

    return index;

}

/**
 * Optimization method; hide all slides that are far away
 * from the present slide.
 */
function updateSlidesVisibility() {

    // Select all slides and convert the NodeList result to
    // an array
    var horizontalSlides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ),
        horizontalSlidesLength = horizontalSlides.length,
        distanceX,
        distanceY;

    if( horizontalSlidesLength && typeof indexh !== 'undefined' ) {

        // The number of steps away from the present slide that will
        // be visible
        var viewDistance = isOverview() ? 10 : config.viewDistance;

        // Limit view distance on weaker devices
        if( isMobileDevice ) {
            viewDistance = isOverview() ? 6 : 2;
        }

        // All slides need to be visible when exporting to PDF
        if( isPrintingPDF() ) {
            viewDistance = Number.MAX_VALUE;
        }

        for( var x = 0; x < horizontalSlidesLength; x++ ) {
            var horizontalSlide = horizontalSlides[x];

            var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) ),
                verticalSlidesLength = verticalSlides.length;

            // Determine how far away this slide is from the present
            distanceX = Math.abs( ( indexh || 0 ) - x ) || 0;

            // If the presentation is looped, distance should measure
            // 1 between the first and last slides
            if( config.loop ) {
                distanceX = Math.abs( ( ( indexh || 0 ) - x ) % ( horizontalSlidesLength - viewDistance ) ) || 0;
            }

            // Show the horizontal slide if it's within the view distance
            if( distanceX < viewDistance ) {
                showSlide( horizontalSlide );
            }
            else {
                hideSlide( horizontalSlide );
            }

            if( verticalSlidesLength ) {

                var oy = getPreviousVerticalIndex( horizontalSlide );

                for( var y = 0; y < verticalSlidesLength; y++ ) {
                    var verticalSlide = verticalSlides[y];

                    distanceY = x === ( indexh || 0 ) ? Math.abs( ( indexv || 0 ) - y ) : Math.abs( y - oy );

                    if( distanceX + distanceY < viewDistance ) {
                        showSlide( verticalSlide );
                    }
                    else {
                        hideSlide( verticalSlide );
                    }
                }

            }
        }

    }

}

/**
 * Updates the progress bar to reflect the current slide.
 */
function updateProgress() {

    // Update progress if enabled
    if( config.progress && dom.progressbar ) {

        dom.progressbar.style.width = getProgress() * dom.wrapper.offsetWidth + 'px';

    }

}

/**
 * Updates the slide number div to reflect the current slide.
 *
 * Slide number format can be defined as a string using the
 * following variables:
 *  h: current slide's horizontal index
 *  v: current slide's vertical index
 *  c: current slide index (flattened)
 *  t: total number of slides (flattened)
 */
function updateSlideNumber() {

    // Update slide number if enabled
    if( config.slideNumber && dom.slideNumber) {

        // Default to only showing the current slide number
        var format = 'c';

        // Check if a custom slide number format is available
        if( typeof config.slideNumber === 'string' ) {
            format = config.slideNumber;
        }

        dom.slideNumber.innerHTML = format.replace( /h/g, indexh )
            .replace( /v/g, indexv )
            .replace( /c/g, getSlidePastCount() + 1 )
            .replace( /t/g, getTotalSlides() );
    }

}

/**
 * Updates the state of all control/navigation arrows.
 */
function updateControls() {

    var routes = availableRoutes();
    var fragments = availableFragments();

    // Remove the 'enabled' class from all directions
    dom.controlsLeft.concat( dom.controlsRight )
        .concat( dom.controlsUp )
        .concat( dom.controlsDown )
        .concat( dom.controlsPrev )
        .concat( dom.controlsNext ).forEach( function( node ) {
            node.classList.remove( 'enabled' );
            node.classList.remove( 'fragmented' );
        } );

    // Add the 'enabled' class to the available routes
    if( routes.left ) dom.controlsLeft.forEach( function( el ) { el.classList.add( 'enabled' );     } );
    if( routes.right ) dom.controlsRight.forEach( function( el ) { el.classList.add( 'enabled' ); } );
    if( routes.up ) dom.controlsUp.forEach( function( el ) { el.classList.add( 'enabled' ); } );
    if( routes.down ) dom.controlsDown.forEach( function( el ) { el.classList.add( 'enabled' ); } );

    // Prev/next buttons
    if( routes.left || routes.up ) dom.controlsPrev.forEach( function( el ) { el.classList.add( 'enabled' ); } );
    if( routes.right || routes.down ) dom.controlsNext.forEach( function( el ) { el.classList.add( 'enabled' ); } );

    // Highlight fragment directions
    if( currentSlide ) {

        // Always apply fragment decorator to prev/next buttons
        if( fragments.prev ) dom.controlsPrev.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
        if( fragments.next ) dom.controlsNext.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );

        // Apply fragment decorators to directional buttons based on
        // what slide axis they are in
        if( isVerticalSlide( currentSlide ) ) {
            if( fragments.prev ) dom.controlsUp.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
            if( fragments.next ) dom.controlsDown.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
        }
        else {
            if( fragments.prev ) dom.controlsLeft.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
            if( fragments.next ) dom.controlsRight.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
        }

    }

}

/**
 * Updates the background elements to reflect the current
 * slide.
 *
 * @param {Boolean} includeAll If true, the backgrounds of
 * all vertical slides (not just the present) will be updated.
 */
function updateBackground( includeAll ) {

    var currentBackground = null;

    // Reverse past/future classes when in RTL mode
    var horizontalPast = config.rtl ? 'future' : 'past',
        horizontalFuture = config.rtl ? 'past' : 'future';

    // Update the classes of all backgrounds to match the
    // states of their slides (past/present/future)
    toArray( dom.background.childNodes ).forEach( function( backgroundh, h ) {

        backgroundh.classList.remove( 'past' );
        backgroundh.classList.remove( 'present' );
        backgroundh.classList.remove( 'future' );

        if( h < indexh ) {
            backgroundh.classList.add( horizontalPast );
        }
        else if ( h > indexh ) {
            backgroundh.classList.add( horizontalFuture );
        }
        else {
            backgroundh.classList.add( 'present' );

            // Store a reference to the current background element
            currentBackground = backgroundh;
        }

        if( includeAll || h === indexh ) {
            toArray( backgroundh.querySelectorAll( '.slide-background' ) ).forEach( function( backgroundv, v ) {

                backgroundv.classList.remove( 'past' );
                backgroundv.classList.remove( 'present' );
                backgroundv.classList.remove( 'future' );

                if( v < indexv ) {
                    backgroundv.classList.add( 'past' );
                }
                else if ( v > indexv ) {
                    backgroundv.classList.add( 'future' );
                }
                else {
                    backgroundv.classList.add( 'present' );

                    // Only if this is the present horizontal and vertical slide
                    if( h === indexh ) currentBackground = backgroundv;
                }

            } );
        }

    } );

    // Stop any currently playing video background
    if( previousBackground ) {

        var previousVideo = previousBackground.querySelector( 'video' );
        if( previousVideo ) previousVideo.pause();

    }

    if( currentBackground ) {

        // Start video playback
        var currentVideo = currentBackground.querySelector( 'video' );
        if( currentVideo ) {
            currentVideo.currentTime = 0;
            currentVideo.play();
        }

        var backgroundImageURL = currentBackground.style.backgroundImage || '';

        // Restart GIFs (doesn't work in Firefox)
        if( /\.gif/i.test( backgroundImageURL ) ) {
            currentBackground.style.backgroundImage = '';
            window.getComputedStyle( currentBackground ).opacity;
            currentBackground.style.backgroundImage = backgroundImageURL;
        }

        // Don't transition between identical backgrounds. This
        // prevents unwanted flicker.
        var previousBackgroundHash = previousBackground ? previousBackground.getAttribute( 'data-background-hash' ) : null;
        var currentBackgroundHash = currentBackground.getAttribute( 'data-background-hash' );
        if( currentBackgroundHash && currentBackgroundHash === previousBackgroundHash && currentBackground !== previousBackground ) {
            dom.background.classList.add( 'no-transition' );
        }

        previousBackground = currentBackground;

    }

    // If there's a background brightness flag for this slide,
    // bubble it to the .reveal container
    if( currentSlide ) {
        [ 'has-light-background', 'has-dark-background' ].forEach( function( classToBubble ) {
            if( currentSlide.classList.contains( classToBubble ) ) {
                dom.wrapper.classList.add( classToBubble );
            }
            else {
                dom.wrapper.classList.remove( classToBubble );
            }
        } );
    }

    // Allow the first background to apply without transition
    setTimeout( function() {
        dom.background.classList.remove( 'no-transition' );
    }, 1 );

}

/**
 * Updates the position of the parallax background based
 * on the current slide index.
 */
function updateParallax() {

    if( config.parallaxBackgroundImage ) {

        var horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
            verticalSlides = dom.wrapper.querySelectorAll( VERTICAL_SLIDES_SELECTOR );

        var backgroundSize = dom.background.style.backgroundSize.split( ' ' ),
            backgroundWidth, backgroundHeight;

        if( backgroundSize.length === 1 ) {
            backgroundWidth = backgroundHeight = parseInt( backgroundSize[0], 10 );
        }
        else {
            backgroundWidth = parseInt( backgroundSize[0], 10 );
            backgroundHeight = parseInt( backgroundSize[1], 10 );
        }

        var slideWidth = dom.background.offsetWidth,
            horizontalSlideCount = horizontalSlides.length,
            horizontalOffsetMultiplier,
            horizontalOffset;

        if( typeof config.parallaxBackgroundHorizontal === 'number' ) {
            horizontalOffsetMultiplier = config.parallaxBackgroundHorizontal;
        }
        else {
            horizontalOffsetMultiplier = ( backgroundWidth - slideWidth ) / ( horizontalSlideCount-1 );
        }

        horizontalOffset = horizontalOffsetMultiplier * indexh * -1;

        var slideHeight = dom.background.offsetHeight,
            verticalSlideCount = verticalSlides.length,
            verticalOffsetMultiplier,
            verticalOffset;

        if( typeof config.parallaxBackgroundVertical === 'number' ) {
            verticalOffsetMultiplier = config.parallaxBackgroundVertical;
        }
        else {
            verticalOffsetMultiplier = ( backgroundHeight - slideHeight ) / ( verticalSlideCount-1 );
        }

        verticalOffset = verticalSlideCount > 0 ?  verticalOffsetMultiplier * indexv * 1 : 0;

        dom.background.style.backgroundPosition = horizontalOffset + 'px ' + -verticalOffset + 'px';

    }

}

/**
 * Called when the given slide is within the configured view
 * distance. Shows the slide element and loads any content
 * that is set to load lazily (data-src).
 */
function showSlide( slide ) {

    // Show the slide element
    slide.style.display = 'block';

    // Media elements with data-src attributes
    toArray( slide.querySelectorAll( 'img[data-src], video[data-src], audio[data-src]' ) ).forEach( function( element ) {
        element.setAttribute( 'src', element.getAttribute( 'data-src' ) );
        element.removeAttribute( 'data-src' );
    } );

    // Media elements with <source> children
    toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( media ) {
        var sources = 0;

        toArray( media.querySelectorAll( 'source[data-src]' ) ).forEach( function( source ) {
            source.setAttribute( 'src', source.getAttribute( 'data-src' ) );
            source.removeAttribute( 'data-src' );
            sources += 1;
        } );

        // If we rewrote sources for this video/audio element, we need
        // to manually tell it to load from its new origin
        if( sources > 0 ) {
            media.load();
        }
    } );

    // Show the corresponding background element
    var indices = getIndices( slide );
    var background = getSlideBackground( indices.h, indices.v );
    if( background ) {
        background.style.display = 'block';

        // If the background contains media, load it
        if( background.hasAttribute( 'data-loaded' ) === false ) {
            background.setAttribute( 'data-loaded', 'true' );

            var backgroundImage = slide.getAttribute( 'data-background-image' ),
                backgroundVideo = slide.getAttribute( 'data-background-video' ),
                backgroundVideoLoop = slide.hasAttribute( 'data-background-video-loop' ),
                backgroundIframe = slide.getAttribute( 'data-background-iframe' );

            // Images
            if( backgroundImage ) {
                background.style.backgroundImage = 'url('+ backgroundImage +')';
            }
            // Videos
            else if ( backgroundVideo && !isSpeakerNotes() ) {
                var video = document.createElement( 'video' );

                if( backgroundVideoLoop ) {
                    video.setAttribute( 'loop', '' );
                }

                // Support comma separated lists of video sources
                backgroundVideo.split( ',' ).forEach( function( source ) {
                    video.innerHTML += '<source src="'+ source +'">';
                } );

                background.appendChild( video );
            }
            // Iframes
            else if( backgroundIframe ) {
                var iframe = document.createElement( 'iframe' );
                iframe.setAttribute( 'src', backgroundIframe );
                iframe.style.width  = '100%';
                iframe.style.height = '100%';
                iframe.style.maxHeight = '100%';
                iframe.style.maxWidth = '100%';

                background.appendChild( iframe );
            }
        }
    }

}

/**
 * Called when the given slide is moved outside of the
 * configured view distance.
 */
function hideSlide( slide ) {

    // Hide the slide element
    slide.style.display = 'none';

    // Hide the corresponding background element
    var indices = getIndices( slide );
    var background = getSlideBackground( indices.h, indices.v );
    if( background ) {
        background.style.display = 'none';
    }

}

/**
 * Determine what available routes there are for navigation.
 *
 * @return {Object} containing four booleans: left/right/up/down
 */
function availableRoutes() {

    var horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
        verticalSlides = dom.wrapper.querySelectorAll( VERTICAL_SLIDES_SELECTOR );

    var routes = {
        left: indexh > 0 || config.loop,
        right: indexh < horizontalSlides.length - 1 || config.loop,
        up: indexv > 0,
        down: indexv < verticalSlides.length - 1
    };

    // reverse horizontal controls for rtl
    if( config.rtl ) {
        var left = routes.left;
        routes.left = routes.right;
        routes.right = left;
    }

    return routes;

}

/**
 * Returns an object describing the available fragment
 * directions.
 *
 * @return {Object} two boolean properties: prev/next
 */
function availableFragments() {

    if( currentSlide && config.fragments ) {
        var fragments = currentSlide.querySelectorAll( '.fragment' );
        var hiddenFragments = currentSlide.querySelectorAll( '.fragment:not(.visible)' );

        return {
            prev: fragments.length - hiddenFragments.length > 0,
            next: !!hiddenFragments.length
        };
    }
    else {
        return { prev: false, next: false };
    }

}

/**
 * Enforces origin-specific format rules for embedded media.
 */
function formatEmbeddedContent() {

    var _appendParamToIframeSource = function( sourceAttribute, sourceURL, param ) {
        toArray( dom.slides.querySelectorAll( 'iframe['+ sourceAttribute +'*="'+ sourceURL +'"]' ) ).forEach( function( el ) {
            var src = el.getAttribute( sourceAttribute );
            if( src && src.indexOf( param ) === -1 ) {
                el.setAttribute( sourceAttribute, src + ( !/\?/.test( src ) ? '?' : '&' ) + param );
            }
        });
    };

    // YouTube frames must include "?enablejsapi=1"
    _appendParamToIframeSource( 'src', 'youtube.com/embed/', 'enablejsapi=1' );
    _appendParamToIframeSource( 'data-src', 'youtube.com/embed/', 'enablejsapi=1' );

    // Vimeo frames must include "?api=1"
    _appendParamToIframeSource( 'src', 'player.vimeo.com/', 'api=1' );
    _appendParamToIframeSource( 'data-src', 'player.vimeo.com/', 'api=1' );

}

/**
 * Start playback of any embedded content inside of
 * the targeted slide.
 */
function startEmbeddedContent( slide ) {

    if( slide && !isSpeakerNotes() ) {
        // Restart GIFs
        toArray( slide.querySelectorAll( 'img[src$=".gif"]' ) ).forEach( function( el ) {
            // Setting the same unchanged source like this was confirmed
            // to work in Chrome, FF & Safari
            el.setAttribute( 'src', el.getAttribute( 'src' ) );
        } );

        // HTML5 media elements
        toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
            if( el.hasAttribute( 'data-autoplay' ) && typeof el.play === 'function' ) {
                el.play();
            }
        } );

        // Normal iframes
        toArray( slide.querySelectorAll( 'iframe[src]' ) ).forEach( function( el ) {
            startEmbeddedIframe( { target: el } );
        } );

        // Lazy loading iframes
        toArray( slide.querySelectorAll( 'iframe[data-src]' ) ).forEach( function( el ) {
            if( el.getAttribute( 'src' ) !== el.getAttribute( 'data-src' ) ) {
                el.removeEventListener( 'load', startEmbeddedIframe ); // remove first to avoid dupes
                el.addEventListener( 'load', startEmbeddedIframe );
                el.setAttribute( 'src', el.getAttribute( 'data-src' ) );
            }
        } );
    }

}

/**
 * "Starts" the content of an embedded iframe using the
 * postmessage API.
 */
function startEmbeddedIframe( event ) {

    var iframe = event.target;

    // YouTube postMessage API
    if( /youtube\.com\/embed\//.test( iframe.getAttribute( 'src' ) ) && iframe.hasAttribute( 'data-autoplay' ) ) {
        iframe.contentWindow.postMessage( '{"event":"command","func":"playVideo","args":""}', '*' );
    }
    // Vimeo postMessage API
    else if( /player\.vimeo\.com\//.test( iframe.getAttribute( 'src' ) ) && iframe.hasAttribute( 'data-autoplay' ) ) {
        iframe.contentWindow.postMessage( '{"method":"play"}', '*' );
    }
    // Generic postMessage API
    else {
        iframe.contentWindow.postMessage( 'slide:start', '*' );
    }

}

/**
 * Stop playback of any embedded content inside of
 * the targeted slide.
 */
function stopEmbeddedContent( slide ) {

    if( slide && slide.parentNode ) {
        // HTML5 media elements
        toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
            if( !el.hasAttribute( 'data-ignore' ) && typeof el.pause === 'function' ) {
                el.pause();
            }
        } );

        // Generic postMessage API for non-lazy loaded iframes
        toArray( slide.querySelectorAll( 'iframe' ) ).forEach( function( el ) {
            el.contentWindow.postMessage( 'slide:stop', '*' );
            el.removeEventListener( 'load', startEmbeddedIframe );
        });

        // YouTube postMessage API
        toArray( slide.querySelectorAll( 'iframe[src*="youtube.com/embed/"]' ) ).forEach( function( el ) {
            if( !el.hasAttribute( 'data-ignore' ) && typeof el.contentWindow.postMessage === 'function' ) {
                el.contentWindow.postMessage( '{"event":"command","func":"pauseVideo","args":""}', '*' );
            }
        });

        // Vimeo postMessage API
        toArray( slide.querySelectorAll( 'iframe[src*="player.vimeo.com/"]' ) ).forEach( function( el ) {
            if( !el.hasAttribute( 'data-ignore' ) && typeof el.contentWindow.postMessage === 'function' ) {
                el.contentWindow.postMessage( '{"method":"pause"}', '*' );
            }
        });

        // Lazy loading iframes
        toArray( slide.querySelectorAll( 'iframe[data-src]' ) ).forEach( function( el ) {
            // Only removing the src doesn't actually unload the frame
            // in all browsers (Firefox) so we set it to blank first
            el.setAttribute( 'src', 'about:blank' );
            el.removeAttribute( 'src' );
        } );
    }

}

/**
 * Returns the number of past slides. This can be used as a global
 * flattened index for slides.
 */
function getSlidePastCount() {

    var horizontalSlides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );

    // The number of past slides
    var pastCount = 0;

    // Step through all slides and count the past ones
    mainLoop: for( var i = 0; i < horizontalSlides.length; i++ ) {

        var horizontalSlide = horizontalSlides[i];
        var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) );

        for( var j = 0; j < verticalSlides.length; j++ ) {

            // Stop as soon as we arrive at the present
            if( verticalSlides[j].classList.contains( 'present' ) ) {
                break mainLoop;
            }

            pastCount++;

        }

        // Stop as soon as we arrive at the present
        if( horizontalSlide.classList.contains( 'present' ) ) {
            break;
        }

        // Don't count the wrapping section for vertical slides
        if( horizontalSlide.classList.contains( 'stack' ) === false ) {
            pastCount++;
        }

    }

    return pastCount;

}

/**
 * Returns a value ranging from 0-1 that represents
 * how far into the presentation we have navigated.
 */
function getProgress() {

    // The number of past and total slides
    var totalCount = getTotalSlides();
    var pastCount = getSlidePastCount();

    if( currentSlide ) {

        var allFragments = currentSlide.querySelectorAll( '.fragment' );

        // If there are fragments in the current slide those should be
        // accounted for in the progress.
        if( allFragments.length > 0 ) {
            var visibleFragments = currentSlide.querySelectorAll( '.fragment.visible' );

            // This value represents how big a portion of the slide progress
            // that is made up by its fragments (0-1)
            var fragmentWeight = 0.9;

            // Add fragment progress to the past slide count
            pastCount += ( visibleFragments.length / allFragments.length ) * fragmentWeight;
        }

    }

    return pastCount / ( totalCount - 1 );

}

/**
 * Checks if this presentation is running inside of the
 * speaker notes window.
 */
function isSpeakerNotes() {

    return !!window.location.search.match( /receiver/gi );

}

/**
 * Reads the current URL (hash) and navigates accordingly.
 */
function readURL() {

    var hash = window.location.hash;

    // Attempt to parse the hash as either an index or name
    var bits = hash.slice( 2 ).split( '/' ),
        name = hash.replace( /#|\//gi, '' );

    // If the first bit is invalid and there is a name we can
    // assume that this is a named link
    if( isNaN( parseInt( bits[0], 10 ) ) && name.length ) {
        var element;

        // Ensure the named link is a valid HTML ID attribute
        if( /^[a-zA-Z][\w:.-]*$/.test( name ) ) {
            // Find the slide with the specified ID
            element = document.getElementById( name );
        }

        if( element ) {
            // Find the position of the named slide and navigate to it
            var indices = Reveal.getIndices( element );
            slide( indices.h, indices.v );
        }
        // If the slide doesn't exist, navigate to the current slide
        else {
            slide( indexh || 0, indexv || 0 );
        }
    }
    else {
        // Read the index components of the hash
        var h = parseInt( bits[0], 10 ) || 0,
            v = parseInt( bits[1], 10 ) || 0;

        if( h !== indexh || v !== indexv ) {
            slide( h, v );
        }
    }

}

/**
 * Updates the page URL (hash) to reflect the current
 * state.
 *
 * @param {Number} delay The time in ms to wait before
 * writing the hash
 */
function writeURL( delay ) {

    if( config.history ) {

        // Make sure there's never more than one timeout running
        clearTimeout( writeURLTimeout );

        // If a delay is specified, timeout this call
        if( typeof delay === 'number' ) {
            writeURLTimeout = setTimeout( writeURL, delay );
        }
        else if( currentSlide ) {
            var url = '/';

            // Attempt to create a named link based on the slide's ID
            var id = currentSlide.getAttribute( 'id' );
            if( id ) {
                id = id.toLowerCase();
                id = id.replace( /[^a-zA-Z0-9\-\_\:\.]/g, '' );
            }

            // If the current slide has an ID, use that as a named link
            if( typeof id === 'string' && id.length ) {
                url = '/' + id;
            }
            // Otherwise use the /h/v index
            else {
                if( indexh > 0 || indexv > 0 ) url += indexh;
                if( indexv > 0 ) url += '/' + indexv;
            }

            window.location.hash = url;
        }
    }

}

/**
 * Retrieves the h/v location of the current, or specified,
 * slide.
 *
 * @param {HTMLElement} slide If specified, the returned
 * index will be for this slide rather than the currently
 * active one
 *
 * @return {Object} { h: <int>, v: <int>, f: <int> }
 */
function getIndices( slide ) {

    // By default, return the current indices
    var h = indexh,
        v = indexv,
        f;

    // If a slide is specified, return the indices of that slide
    if( slide ) {
        var isVertical = isVerticalSlide( slide );
        var slideh = isVertical ? slide.parentNode : slide;

        // Select all horizontal slides
        var horizontalSlides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );

        // Now that we know which the horizontal slide is, get its index
        h = Math.max( horizontalSlides.indexOf( slideh ), 0 );

        // Assume we're not vertical
        v = undefined;

        // If this is a vertical slide, grab the vertical index
        if( isVertical ) {
            v = Math.max( toArray( slide.parentNode.querySelectorAll( 'section' ) ).indexOf( slide ), 0 );
        }
    }

    if( !slide && currentSlide ) {
        var hasFragments = currentSlide.querySelectorAll( '.fragment' ).length > 0;
        if( hasFragments ) {
            var currentFragment = currentSlide.querySelector( '.current-fragment' );
            if( currentFragment && currentFragment.hasAttribute( 'data-fragment-index' ) ) {
                f = parseInt( currentFragment.getAttribute( 'data-fragment-index' ), 10 );
            }
            else {
                f = currentSlide.querySelectorAll( '.fragment.visible' ).length - 1;
            }
        }
    }

    return { h: h, v: v, f: f };

}

/**
 * Retrieves the total number of slides in this presentation.
 */
function getTotalSlides() {

    return dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ':not(.stack)' ).length;

}

/**
 * Returns the slide element matching the specified index.
 */
function getSlide( x, y ) {

    var horizontalSlide = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR )[ x ];
    var verticalSlides = horizontalSlide && horizontalSlide.querySelectorAll( 'section' );

    if( verticalSlides && verticalSlides.length && typeof y === 'number' ) {
        return verticalSlides ? verticalSlides[ y ] : undefined;
    }

    return horizontalSlide;

}

/**
 * Returns the background element for the given slide.
 * All slides, even the ones with no background properties
 * defined, have a background element so as long as the
 * index is valid an element will be returned.
 */
function getSlideBackground( x, y ) {

    // When printing to PDF the slide backgrounds are nested
    // inside of the slides
    if( isPrintingPDF() ) {
        var slide = getSlide( x, y );
        if( slide ) {
            var background = slide.querySelector( '.slide-background' );
            if( background && background.parentNode === slide ) {
                return background;
            }
        }

        return undefined;
    }

    var horizontalBackground = dom.wrapper.querySelectorAll( '.backgrounds>.slide-background' )[ x ];
    var verticalBackgrounds = horizontalBackground && horizontalBackground.querySelectorAll( '.slide-background' );

    if( verticalBackgrounds && verticalBackgrounds.length && typeof y === 'number' ) {
        return verticalBackgrounds ? verticalBackgrounds[ y ] : undefined;
    }

    return horizontalBackground;

}

/**
 * Retrieves the current state of the presentation as
 * an object. This state can then be restored at any
 * time.
 */
function getState() {

    var indices = getIndices();

    return {
        indexh: indices.h,
        indexv: indices.v,
        indexf: indices.f,
        paused: isPaused(),
        overview: isOverview()
    };

}

/**
 * Restores the presentation to the given state.
 *
 * @param {Object} state As generated by getState()
 */
function setState( state ) {

    if( typeof state === 'object' ) {
        slide( deserialize( state.indexh ), deserialize( state.indexv ), deserialize( state.indexf ) );

        var pausedFlag = deserialize( state.paused ),
            overviewFlag = deserialize( state.overview );

        if( typeof pausedFlag === 'boolean' && pausedFlag !== isPaused() ) {
            togglePause( pausedFlag );
        }

        if( typeof overviewFlag === 'boolean' && overviewFlag !== isOverview() ) {
            toggleOverview( overviewFlag );
        }
    }

}

/**
 * Return a sorted fragments list, ordered by an increasing
 * "data-fragment-index" attribute.
 *
 * Fragments will be revealed in the order that they are returned by
 * this function, so you can use the index attributes to control the
 * order of fragment appearance.
 *
 * To maintain a sensible default fragment order, fragments are presumed
 * to be passed in document order. This function adds a "fragment-index"
 * attribute to each node if such an attribute is not already present,
 * and sets that attribute to an integer value which is the position of
 * the fragment within the fragments list.
 */
function sortFragments( fragments ) {

    fragments = toArray( fragments );

    var ordered = [],
        unordered = [],
        sorted = [];

    // Group ordered and unordered elements
    fragments.forEach( function( fragment, i ) {
        if( fragment.hasAttribute( 'data-fragment-index' ) ) {
            var index = parseInt( fragment.getAttribute( 'data-fragment-index' ), 10 );

            if( !ordered[index] ) {
                ordered[index] = [];
            }

            ordered[index].push( fragment );
        }
        else {
            unordered.push( [ fragment ] );
        }
    } );

    // Append fragments without explicit indices in their
    // DOM order
    ordered = ordered.concat( unordered );

    // Manually count the index up per group to ensure there
    // are no gaps
    var index = 0;

    // Push all fragments in their sorted order to an array,
    // this flattens the groups
    ordered.forEach( function( group ) {
        group.forEach( function( fragment ) {
            sorted.push( fragment );
            fragment.setAttribute( 'data-fragment-index', index );
        } );

        index ++;
    } );

    return sorted;

}

/**
 * Navigate to the specified slide fragment.
 *
 * @param {Number} index The index of the fragment that
 * should be shown, -1 means all are invisible
 * @param {Number} offset Integer offset to apply to the
 * fragment index
 *
 * @return {Boolean} true if a change was made in any
 * fragments visibility as part of this call
 */
function navigateFragment( index, offset ) {

    if( currentSlide && config.fragments ) {

        var fragments = sortFragments( currentSlide.querySelectorAll( '.fragment' ) );
        if( fragments.length ) {

            // If no index is specified, find the current
            if( typeof index !== 'number' ) {
                var lastVisibleFragment = sortFragments( currentSlide.querySelectorAll( '.fragment.visible' ) ).pop();

                if( lastVisibleFragment ) {
                    index = parseInt( lastVisibleFragment.getAttribute( 'data-fragment-index' ) || 0, 10 );
                }
                else {
                    index = -1;
                }
            }

            // If an offset is specified, apply it to the index
            if( typeof offset === 'number' ) {
                index += offset;
            }

            var fragmentsShown = [],
                fragmentsHidden = [];

            toArray( fragments ).forEach( function( element, i ) {

                if( element.hasAttribute( 'data-fragment-index' ) ) {
                    i = parseInt( element.getAttribute( 'data-fragment-index' ), 10 );
                }

                // Visible fragments
                if( i <= index ) {
                    if( !element.classList.contains( 'visible' ) ) fragmentsShown.push( element );
                    element.classList.add( 'visible' );
                    element.classList.remove( 'current-fragment' );

                    // Announce the fragments one by one to the Screen Reader
                    dom.statusDiv.textContent = element.textContent;

                    if( i === index ) {
                        element.classList.add( 'current-fragment' );
                    }
                }
                // Hidden fragments
                else {
                    if( element.classList.contains( 'visible' ) ) fragmentsHidden.push( element );
                    element.classList.remove( 'visible' );
                    element.classList.remove( 'current-fragment' );
                }

            } );

            if( fragmentsHidden.length ) {
                dispatchEvent( 'fragmenthidden', { fragment: fragmentsHidden[0], fragments: fragmentsHidden } );
            }

            if( fragmentsShown.length ) {
                dispatchEvent( 'fragmentshown', { fragment: fragmentsShown[0], fragments: fragmentsShown } );
            }

            updateControls();
            updateProgress();

            return !!( fragmentsShown.length || fragmentsHidden.length );

        }

    }

    return false;

}

/**
 * Navigate to the next slide fragment.
 *
 * @return {Boolean} true if there was a next fragment,
 * false otherwise
 */
function nextFragment() {

    return navigateFragment( null, 1 );

}

/**
 * Navigate to the previous slide fragment.
 *
 * @return {Boolean} true if there was a previous fragment,
 * false otherwise
 */
function previousFragment() {

    return navigateFragment( null, -1 );

}

/**
 * Cues a new automated slide if enabled in the config.
 */
function cueAutoSlide() {

    cancelAutoSlide();

    if( currentSlide ) {

        var currentFragment = currentSlide.querySelector( '.current-fragment' );

        var fragmentAutoSlide = currentFragment ? currentFragment.getAttribute( 'data-autoslide' ) : null;
        var parentAutoSlide = currentSlide.parentNode ? currentSlide.parentNode.getAttribute( 'data-autoslide' ) : null;
        var slideAutoSlide = currentSlide.getAttribute( 'data-autoslide' );

        // Pick value in the following priority order:
        // 1. Current fragment's data-autoslide
        // 2. Current slide's data-autoslide
        // 3. Parent slide's data-autoslide
        // 4. Global autoSlide setting
        if( fragmentAutoSlide ) {
            autoSlide = parseInt( fragmentAutoSlide, 10 );
        }
        else if( slideAutoSlide ) {
            autoSlide = parseInt( slideAutoSlide, 10 );
        }
        else if( parentAutoSlide ) {
            autoSlide = parseInt( parentAutoSlide, 10 );
        }
        else {
            autoSlide = config.autoSlide;
        }

        // If there are media elements with data-autoplay,
        // automatically set the autoSlide duration to the
        // length of that media. Not applicable if the slide
        // is divided up into fragments.
        if( currentSlide.querySelectorAll( '.fragment' ).length === 0 ) {
            toArray( currentSlide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
                if( el.hasAttribute( 'data-autoplay' ) ) {
                    if( autoSlide && el.duration * 1000 > autoSlide ) {
                        autoSlide = ( el.duration * 1000 ) + 1000;
                    }
                }
            } );
        }

        // Cue the next auto-slide if:
        // - There is an autoSlide value
        // - Auto-sliding isn't paused by the user
        // - The presentation isn't paused
        // - The overview isn't active
        // - The presentation isn't over
        if( autoSlide && !autoSlidePaused && !isPaused() && !isOverview() && ( !Reveal.isLastSlide() || availableFragments().next || config.loop === true ) ) {
            autoSlideTimeout = setTimeout( navigateNext, autoSlide );
            autoSlideStartTime = Date.now();
        }

        if( autoSlidePlayer ) {
            autoSlidePlayer.setPlaying( autoSlideTimeout !== -1 );
        }

    }

}

/**
 * Cancels any ongoing request to auto-slide.
 */
function cancelAutoSlide() {

    clearTimeout( autoSlideTimeout );
    autoSlideTimeout = -1;

}

function pauseAutoSlide() {

    if( autoSlide && !autoSlidePaused ) {
        autoSlidePaused = true;
        dispatchEvent( 'autoslidepaused' );
        clearTimeout( autoSlideTimeout );

        if( autoSlidePlayer ) {
            autoSlidePlayer.setPlaying( false );
        }
    }

}

function resumeAutoSlide() {

    if( autoSlide && autoSlidePaused ) {
        autoSlidePaused = false;
        dispatchEvent( 'autoslideresumed' );
        cueAutoSlide();
    }

}

function navigateLeft() {

    // Reverse for RTL
    if( config.rtl ) {
        if( ( isOverview() || nextFragment() === false ) && availableRoutes().left ) {
            slide( indexh + 1 );
        }
    }
    // Normal navigation
    else if( ( isOverview() || previousFragment() === false ) && availableRoutes().left ) {
        slide( indexh - 1 );
    }

}

function navigateRight() {

    // Reverse for RTL
    if( config.rtl ) {
        if( ( isOverview() || previousFragment() === false ) && availableRoutes().right ) {
            slide( indexh - 1 );
        }
    }
    // Normal navigation
    else if( ( isOverview() || nextFragment() === false ) && availableRoutes().right ) {
        slide( indexh + 1 );
    }

}

function navigateUp() {

    // Prioritize hiding fragments
    if( ( isOverview() || previousFragment() === false ) && availableRoutes().up ) {
        slide( indexh, indexv - 1 );
    }

}

function navigateDown() {

    // Prioritize revealing fragments
    if( ( isOverview() || nextFragment() === false ) && availableRoutes().down ) {
        slide( indexh, indexv + 1 );
    }

}

/**
 * Navigates backwards, prioritized in the following order:
 * 1) Previous fragment
 * 2) Previous vertical slide
 * 3) Previous horizontal slide
 */
function navigatePrev() {

    // Prioritize revealing fragments
    if( previousFragment() === false ) {
        if( availableRoutes().up ) {
            navigateUp();
        }
        else {
            // Fetch the previous horizontal slide, if there is one
            var previousSlide;

            if( config.rtl ) {
                previousSlide = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.future' ) ).pop();
            }
            else {
                previousSlide = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.past' ) ).pop();
            }

            if( previousSlide ) {
                var v = ( previousSlide.querySelectorAll( 'section' ).length - 1 ) || undefined;
                var h = indexh - 1;
                slide( h, v );
            }
        }
    }

}

/**
 * The reverse of #navigatePrev().
 */
function navigateNext() {

    // Prioritize revealing fragments
    if( nextFragment() === false ) {
        if( availableRoutes().down ) {
            navigateDown();
        }
        else if( config.rtl ) {
            navigateLeft();
        }
        else {
            navigateRight();
        }
    }

    // If auto-sliding is enabled we need to cue up
    // another timeout
    cueAutoSlide();

}

// --------------------------------------------------------------------//
// ----------------------------- EVENTS -------------------------------//
// --------------------------------------------------------------------//

/**
 * Called by all event handlers that are based on user
 * input.
 */
function onUserInput( event ) {

    if( config.autoSlideStoppable ) {
        pauseAutoSlide();
    }

}

/**
 * Handler for the document level 'keypress' event.
 */
function onDocumentKeyPress( event ) {

    // Check if the pressed key is question mark
    if( event.shiftKey && event.charCode === 63 ) {
        if( dom.overlay ) {
            closeOverlay();
        }
        else {
            showHelp( true );
        }
    }

}

/**
 * Handler for the document level 'keydown' event.
 */
function onDocumentKeyDown( event ) {

    // If there's a condition specified and it returns false,
    // ignore this event
    if( typeof config.keyboardCondition === 'function' && config.keyboardCondition() === false ) {
        return true;
    }

    // Remember if auto-sliding was paused so we can toggle it
    var autoSlideWasPaused = autoSlidePaused;

    onUserInput( event );

    // Check if there's a focused element that could be using
    // the keyboard
    var activeElementIsCE = document.activeElement && document.activeElement.contentEditable !== 'inherit';
    var activeElementIsInput = document.activeElement && document.activeElement.tagName && /input|textarea/i.test( document.activeElement.tagName );

    // Disregard the event if there's a focused element or a
    // keyboard modifier key is present
    if( activeElementIsCE || activeElementIsInput || (event.shiftKey && event.keyCode !== 32) || event.altKey || event.ctrlKey || event.metaKey ) return;

    // While paused only allow "unpausing" keyboard events (b and .)
    if( isPaused() && [66,190,191].indexOf( event.keyCode ) === -1 ) {
        return false;
    }

    var triggered = false;

    // 1. User defined key bindings
    if( typeof config.keyboard === 'object' ) {

        for( var key in config.keyboard ) {

            // Check if this binding matches the pressed key
            if( parseInt( key, 10 ) === event.keyCode ) {

                var value = config.keyboard[ key ];

                // Callback function
                if( typeof value === 'function' ) {
                    value.apply( null, [ event ] );
                }
                // String shortcuts to reveal.js API
                else if( typeof value === 'string' && typeof Reveal[ value ] === 'function' ) {
                    Reveal[ value ].call();
                }

                triggered = true;

            }

        }

    }

    // 2. System defined key bindings
    if( triggered === false ) {

        // Assume true and try to prove false
        triggered = true;

        switch( event.keyCode ) {
            // p, page up
            case 80: case 33: navigatePrev(); break;
            // n, page down
            case 78: case 34: navigateNext(); break;
            // h, left
            case 72: case 37: navigateLeft(); break;
            // l, right
            case 76: case 39: navigateRight(); break;
            // k, up
            case 75: case 38: navigateUp(); break;
            // j, down
            case 74: case 40: navigateDown(); break;
            // home
            case 36: slide( 0 ); break;
            // end
            case 35: slide( Number.MAX_VALUE ); break;
            // space
            case 32: isOverview() ? deactivateOverview() : event.shiftKey ? navigatePrev() : navigateNext(); break;
            // return
            case 13: isOverview() ? deactivateOverview() : triggered = false; break;
            // two-spot, semicolon, b, period, Logitech presenter tools "black screen" button
            case 58: case 59: case 66: case 190: case 191: togglePause(); break;
            // f
            case 70: enterFullscreen(); break;
            // a
            case 65: if ( config.autoSlideStoppable ) toggleAutoSlide( autoSlideWasPaused ); break;
            default:
                triggered = false;
        }

    }

    // If the input resulted in a triggered action we should prevent
    // the browsers default behavior
    if( triggered ) {
        event.preventDefault && event.preventDefault();
    }
    // ESC or O key
    else if ( ( event.keyCode === 27 || event.keyCode === 79 ) && features.transforms3d ) {
        if( dom.overlay ) {
            closeOverlay();
        }
        else {
            toggleOverview();
        }

        event.preventDefault && event.preventDefault();
    }

    // If auto-sliding is enabled we need to cue up
    // another timeout
    cueAutoSlide();

}

/**
 * Handler for the 'touchstart' event, enables support for
 * swipe and pinch gestures.
 */
function onTouchStart( event ) {

    touch.startX = event.touches[0].clientX;
    touch.startY = event.touches[0].clientY;
    touch.startCount = event.touches.length;

    // If there's two touches we need to memorize the distance
    // between those two points to detect pinching
    if( event.touches.length === 2 && config.overview ) {
        touch.startSpan = distanceBetween( {
            x: event.touches[1].clientX,
            y: event.touches[1].clientY
        }, {
            x: touch.startX,
            y: touch.startY
        } );
    }

}

/**
 * Handler for the 'touchmove' event.
 */
function onTouchMove( event ) {

    // Each touch should only trigger one action
    if( !touch.captured ) {
        onUserInput( event );

        var currentX = event.touches[0].clientX;
        var currentY = event.touches[0].clientY;

        // If the touch started with two points and still has
        // two active touches; test for the pinch gesture
        if( event.touches.length === 2 && touch.startCount === 2 && config.overview ) {

            // The current distance in pixels between the two touch points
            var currentSpan = distanceBetween( {
                x: event.touches[1].clientX,
                y: event.touches[1].clientY
            }, {
                x: touch.startX,
                y: touch.startY
            } );

            // If the span is larger than the desire amount we've got
            // ourselves a pinch
            if( Math.abs( touch.startSpan - currentSpan ) > touch.threshold ) {
                touch.captured = true;

                if( currentSpan < touch.startSpan ) {
                    activateOverview();
                }
                else {
                    deactivateOverview();
                }
            }

            event.preventDefault();

        }
        // There was only one touch point, look for a swipe
        else if( event.touches.length === 1 && touch.startCount !== 2 ) {

            var deltaX = currentX - touch.startX,
                deltaY = currentY - touch.startY;

            if( deltaX > touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
                touch.captured = true;
                navigateLeft();
            }
            else if( deltaX < -touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
                touch.captured = true;
                navigateRight();
            }
            else if( deltaY > touch.threshold ) {
                touch.captured = true;
                navigateUp();
            }
            else if( deltaY < -touch.threshold ) {
                touch.captured = true;
                navigateDown();
            }

            // If we're embedded, only block touch events if they have
            // triggered an action
            if( config.embedded ) {
                if( touch.captured || isVerticalSlide( currentSlide ) ) {
                    event.preventDefault();
                }
            }
            // Not embedded? Block them all to avoid needless tossing
            // around of the viewport in iOS
            else {
                event.preventDefault();
            }

        }
    }
    // There's a bug with swiping on some Android devices unless
    // the default action is always prevented
    else if( navigator.userAgent.match( /android/gi ) ) {
        event.preventDefault();
    }

}

/**
 * Handler for the 'touchend' event.
 */
function onTouchEnd( event ) {

    touch.captured = false;

}

/**
 * Convert pointer down to touch start.
 */
function onPointerDown( event ) {

    if( event.pointerType === event.MSPOINTER_TYPE_TOUCH || event.pointerType === "touch" ) {
        event.touches = [{ clientX: event.clientX, clientY: event.clientY }];
        onTouchStart( event );
    }

}

/**
 * Convert pointer move to touch move.
 */
function onPointerMove( event ) {

    if( event.pointerType === event.MSPOINTER_TYPE_TOUCH || event.pointerType === "touch" )  {
        event.touches = [{ clientX: event.clientX, clientY: event.clientY }];
        onTouchMove( event );
    }

}

/**
 * Convert pointer up to touch end.
 */
function onPointerUp( event ) {

    if( event.pointerType === event.MSPOINTER_TYPE_TOUCH || event.pointerType === "touch" )  {
        event.touches = [{ clientX: event.clientX, clientY: event.clientY }];
        onTouchEnd( event );
    }

}

/**
 * Handles mouse wheel scrolling, throttled to avoid skipping
 * multiple slides.
 */
function onDocumentMouseScroll( event ) {

    if( Date.now() - lastMouseWheelStep > 600 ) {

        lastMouseWheelStep = Date.now();

        var delta = event.detail || -event.wheelDelta;
        if( delta > 0 ) {
            navigateNext();
        }
        else {
            navigatePrev();
        }

    }

}

/**
 * Clicking on the progress bar results in a navigation to the
 * closest approximate horizontal slide using this equation:
 *
 * ( clickX / presentationWidth ) * numberOfSlides
 */
function onProgressClicked( event ) {

    onUserInput( event );

    event.preventDefault();

    var slidesTotal = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).length;
    var slideIndex = Math.floor( ( event.clientX / dom.wrapper.offsetWidth ) * slidesTotal );

    if( config.rtl ) {
        slideIndex = slidesTotal - slideIndex;
    }

    slide( slideIndex );

}

/**
 * Event handler for navigation control buttons.
 */
function onNavigateLeftClicked( event ) { event.preventDefault(); onUserInput(); navigateLeft(); }
function onNavigateRightClicked( event ) { event.preventDefault(); onUserInput(); navigateRight(); }
function onNavigateUpClicked( event ) { event.preventDefault(); onUserInput(); navigateUp(); }
function onNavigateDownClicked( event ) { event.preventDefault(); onUserInput(); navigateDown(); }
function onNavigatePrevClicked( event ) { event.preventDefault(); onUserInput(); navigatePrev(); }
function onNavigateNextClicked( event ) { event.preventDefault(); onUserInput(); navigateNext(); }

/**
 * Handler for the window level 'hashchange' event.
 */
function onWindowHashChange( event ) {

    readURL();

}

/**
 * Handler for the window level 'resize' event.
 */
function onWindowResize( event ) {

    layout();

}

/**
 * Handle for the window level 'visibilitychange' event.
 */
function onPageVisibilityChange( event ) {

    var isHidden =  document.webkitHidden ||
        document.msHidden ||
        document.hidden;

    // If, after clicking a link or similar and we're coming back,
    // focus the document.body to ensure we can use keyboard shortcuts
    if( isHidden === false && document.activeElement !== document.body ) {
        // Not all elements support .blur() - SVGs among them.
        if( typeof document.activeElement.blur === 'function' ) {
            document.activeElement.blur();
        }
        document.body.focus();
    }

}

/**
 * Invoked when a slide is and we're in the overview.
 */
function onOverviewSlideClicked( event ) {

    // TODO There's a bug here where the event listeners are not
    // removed after deactivating the overview.
    if( eventsAreBound && isOverview() ) {
        event.preventDefault();

        var element = event.target;

        while( element && !element.nodeName.match( /section/gi ) ) {
            element = element.parentNode;
        }

        if( element && !element.classList.contains( 'disabled' ) ) {

            deactivateOverview();

            if( element.nodeName.match( /section/gi ) ) {
                var h = parseInt( element.getAttribute( 'data-index-h' ), 10 ),
                    v = parseInt( element.getAttribute( 'data-index-v' ), 10 );

                slide( h, v );
            }

        }
    }

}

/**
 * Handles clicks on links that are set to preview in the
 * iframe overlay.
 */
function onPreviewLinkClicked( event ) {

    if( event.currentTarget && event.currentTarget.hasAttribute( 'href' ) ) {
        var url = event.currentTarget.getAttribute( 'href' );
        if( url ) {
            showPreview( url );
            event.preventDefault();
        }
    }

}

/**
 * Handles click on the auto-sliding controls element.
 */
function onAutoSlidePlayerClick( event ) {

    // Replay
    if( Reveal.isLastSlide() && config.loop === false ) {
        slide( 0, 0 );
        resumeAutoSlide();
    }
    // Resume
    else if( autoSlidePaused ) {
        resumeAutoSlide();
    }
    // Pause
    else {
        pauseAutoSlide();
    }

}

// --------------------------------------------------------------------//
// ------------------------ PLAYBACK COMPONENT ------------------------//
// --------------------------------------------------------------------//

/**
 * Constructor for the playback component, which displays
 * play/pause/progress controls.
 *
 * @param {HTMLElement} container The component will append
 * itself to this
 * @param {Function} progressCheck A method which will be
 * called frequently to get the current progress on a range
 * of 0-1
 */
function Playback( container, progressCheck ) {

    // Cosmetics
    this.diameter = 50;
    this.thickness = 3;

    // Flags if we are currently playing
    this.playing = false;

    // Current progress on a 0-1 range
    this.progress = 0;

    // Used to loop the animation smoothly
    this.progressOffset = 1;

    this.container = container;
    this.progressCheck = progressCheck;

    this.canvas = document.createElement( 'canvas' );
    this.canvas.className = 'playback';
    this.canvas.width = this.diameter;
    this.canvas.height = this.diameter;
    this.context = this.canvas.getContext( '2d' );

    this.container.appendChild( this.canvas );

    this.render();

}

Playback.prototype.setPlaying = function( value ) {

    var wasPlaying = this.playing;

    this.playing = value;

    // Start repainting if we weren't already
    if( !wasPlaying && this.playing ) {
        this.animate();
    }
    else {
        this.render();
    }

};

Playback.prototype.animate = function() {

    var progressBefore = this.progress;

    this.progress = this.progressCheck();

    // When we loop, offset the progress so that it eases
    // smoothly rather than immediately resetting
    if( progressBefore > 0.8 && this.progress < 0.2 ) {
        this.progressOffset = this.progress;
    }

    this.render();

    if( this.playing ) {
        features.requestAnimationFrameMethod.call( window, this.animate.bind( this ) );
    }

};

/**
 * Renders the current progress and playback state.
 */
Playback.prototype.render = function() {

    var progress = this.playing ? this.progress : 0,
        radius = ( this.diameter / 2 ) - this.thickness,
        x = this.diameter / 2,
        y = this.diameter / 2,
        iconSize = 14;

    // Ease towards 1
    this.progressOffset += ( 1 - this.progressOffset ) * 0.1;

    var endAngle = ( - Math.PI / 2 ) + ( progress * ( Math.PI * 2 ) );
    var startAngle = ( - Math.PI / 2 ) + ( this.progressOffset * ( Math.PI * 2 ) );

    this.context.save();
    this.context.clearRect( 0, 0, this.diameter, this.diameter );

    // Solid background color
    this.context.beginPath();
    this.context.arc( x, y, radius + 2, 0, Math.PI * 2, false );
    this.context.fillStyle = 'rgba( 0, 0, 0, 0.4 )';
    this.context.fill();

    // Draw progress track
    this.context.beginPath();
    this.context.arc( x, y, radius, 0, Math.PI * 2, false );
    this.context.lineWidth = this.thickness;
    this.context.strokeStyle = '#666';
    this.context.stroke();

    if( this.playing ) {
        // Draw progress on top of track
        this.context.beginPath();
        this.context.arc( x, y, radius, startAngle, endAngle, false );
        this.context.lineWidth = this.thickness;
        this.context.strokeStyle = '#fff';
        this.context.stroke();
    }

    this.context.translate( x - ( iconSize / 2 ), y - ( iconSize / 2 ) );

    // Draw play/pause icons
    if( this.playing ) {
        this.context.fillStyle = '#fff';
        this.context.fillRect( 0, 0, iconSize / 2 - 2, iconSize );
        this.context.fillRect( iconSize / 2 + 2, 0, iconSize / 2 - 2, iconSize );
    }
    else {
        this.context.beginPath();
        this.context.translate( 2, 0 );
        this.context.moveTo( 0, 0 );
        this.context.lineTo( iconSize - 2, iconSize / 2 );
        this.context.lineTo( 0, iconSize );
        this.context.fillStyle = '#fff';
        this.context.fill();
    }

    this.context.restore();

};

Playback.prototype.on = function( type, listener ) {
    this.canvas.addEventListener( type, listener, false );
};

Playback.prototype.off = function( type, listener ) {
    this.canvas.removeEventListener( type, listener, false );
};

Playback.prototype.destroy = function() {

    this.playing = false;

    if( this.canvas.parentNode ) {
        this.container.removeChild( this.canvas );
    }

};

// --------------------------------------------------------------------//
// ------------------------------- API --------------------------------//
// --------------------------------------------------------------------//

Reveal = {
    initialize: initialize,
    configure: configure,
    sync: sync,

    // Navigation methods
    slide: slide,
    left: navigateLeft,
    right: navigateRight,
    up: navigateUp,
    down: navigateDown,
    prev: navigatePrev,
    next: navigateNext,

    // Fragment methods
    navigateFragment: navigateFragment,
    prevFragment: previousFragment,
    nextFragment: nextFragment,

    // Deprecated aliases
    navigateTo: slide,
    navigateLeft: navigateLeft,
    navigateRight: navigateRight,
    navigateUp: navigateUp,
    navigateDown: navigateDown,
    navigatePrev: navigatePrev,
    navigateNext: navigateNext,

    // Forces an update in slide layout
    layout: layout,

    // Returns an object with the available routes as booleans (left/right/top/bottom)
    availableRoutes: availableRoutes,

    // Returns an object with the available fragments as booleans (prev/next)
    availableFragments: availableFragments,

    // Toggles the overview mode on/off
    toggleOverview: toggleOverview,

    // Toggles the "black screen" mode on/off
    togglePause: togglePause,

    // Toggles the auto slide mode on/off
    toggleAutoSlide: toggleAutoSlide,

    // State checks
    isOverview: isOverview,
    isPaused: isPaused,
    isAutoSliding: isAutoSliding,

    // Adds or removes all internal event listeners (such as keyboard)
    addEventListeners: addEventListeners,
    removeEventListeners: removeEventListeners,

    // Facility for persisting and restoring the presentation state
    getState: getState,
    setState: setState,

    // Presentation progress on range of 0-1
    getProgress: getProgress,

    // Returns the indices of the current, or specified, slide
    getIndices: getIndices,

    getTotalSlides: getTotalSlides,

    // Returns the slide element at the specified index
    getSlide: getSlide,

    // Returns the slide background element at the specified index
    getSlideBackground: getSlideBackground,

    // Returns the previous slide element, may be null
    getPreviousSlide: function() {
        return previousSlide;
    },

    // Returns the current slide element
    getCurrentSlide: function() {
        return currentSlide;
    },

    // Returns the current scale of the presentation content
    getScale: function() {
        return scale;
    },

    // Returns the current configuration object
    getConfig: function() {
        return config;
    },

    // Helper method, retrieves query string as a key/value hash
    getQueryHash: function() {
        var query = {};

        location.search.replace( /[A-Z0-9]+?=([\w\.%-]*)/gi, function(a) {
            query[ a.split( '=' ).shift() ] = a.split( '=' ).pop();
        } );

        // Basic deserialization
        for( var i in query ) {
            var value = query[ i ];

            query[ i ] = deserialize( unescape( value ) );
        }

        return query;
    },

    // Returns true if we're currently on the first slide
    isFirstSlide: function() {
        return ( indexh === 0 && indexv === 0 );
    },

    // Returns true if we're currently on the last slide
    isLastSlide: function() {
        if( currentSlide ) {
            // Does this slide has next a sibling?
            if( currentSlide.nextElementSibling ) return false;

            // If it's vertical, does its parent have a next sibling?
            if( isVerticalSlide( currentSlide ) && currentSlide.parentNode.nextElementSibling ) return false;

            return true;
        }

        return false;
    },

    // Checks if reveal.js has been loaded and is ready for use
    isReady: function() {
        return loaded;
    },

    // Forward event binding to the reveal DOM element
    addEventListener: function( type, listener, useCapture ) {
        if( 'addEventListener' in window ) {
            ( dom.wrapper || document.querySelector( '.reveal' ) ).addEventListener( type, listener, useCapture );
        }
    },
    removeEventListener: function( type, listener, useCapture ) {
        if( 'addEventListener' in window ) {
            ( dom.wrapper || document.querySelector( '.reveal' ) ).removeEventListener( type, listener, useCapture );
        }
    },

    // Programatically triggers a keyboard event
    triggerKey: function( keyCode ) {
        onDocumentKeyDown( { keyCode: keyCode } );
    }
};

return Reveal;

}));