presentations

reveal.js (168667B)

---

 /*!
  * reveal.js
  * http://revealjs.com
  * MIT licensed
  *
  * Copyright (C) 2019 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;
 
 	// The reveal.js version
 	var VERSION = '3.8.0';
 
 	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',
 		UA = navigator.userAgent,
 
 		// 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: 0.04,
 
 			// Bounds for smallest/largest possible scale to apply to content
 			minScale: 0.2,
 			maxScale: 2.0,
 
 			// Display presentation control arrows
 			controls: true,
 
 			// Help the user learn the controls by providing hints, for example by
 			// bouncing the down arrow when they first encounter a vertical slide
 			controlsTutorial: true,
 
 			// Determines where controls appear, "edges" or "bottom-right"
 			controlsLayout: 'bottom-right',
 
 			// Visibility rule for backwards navigation arrows; "faded", "hidden"
 			// or "visible"
 			controlsBackArrows: 'faded',
 
 			// Display a presentation progress bar
 			progress: true,
 
 			// Display the page number of the current slide
 			// - true:    Show slide number
 			// - false:   Hide slide number
 			//
 			// Can optionally be set as a string that specifies the number formatting:
 			// - "h.v":	  Horizontal . vertical slide number (default)
 			// - "h/v":	  Horizontal / vertical slide number
 			// - "c":	  Flattened slide number
 			// - "c/t":	  Flattened slide number / total slides
 			//
 			// Alternatively, you can provide a function that returns the slide
 			// number for the current slide. The function needs to return an array
 			// with one string [slideNumber] or three strings [n1,delimiter,n2].
 			// See #formatSlideNumber().
 			slideNumber: false,
 
 			// Can be used to limit the contexts in which the slide number appears
 			// - "all":      Always show the slide number
 			// - "print":    Only when printing to PDF
 			// - "speaker":  Only in the speaker view
 			showSlideNumber: 'all',
 
 			// Use 1 based indexing for # links to match slide number (default is zero
 			// based)
 			hashOneBasedIndex: false,
 
 			// Add the current slide number to the URL hash so that reloading the
 			// page/copying the URL will return you to the same slide
 			hash: false,
 
 			// Push each slide change to the browser history.  Implies `hash: true`
 			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,
 
 			// Disables the default reveal.js slide layout so that you can use
 			// custom CSS layout
 			disableLayout: false,
 
 			// 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,
 
 			// Changes the behavior of our navigation directions.
 			//
 			// "default"
 			// Left/right arrow keys step between horizontal slides, up/down
 			// arrow keys step between vertical slides. Space key steps through
 			// all slides (both horizontal and vertical).
 			//
 			// "linear"
 			// Removes the up/down arrows. Left/right arrows step through all
 			// slides (both horizontal and vertical).
 			//
 			// "grid"
 			// When this is enabled, stepping left/right from a vertical stack
 			// to an adjacent vertical stack will land you at the same vertical
 			// index.
 			//
 			// Consider a deck with six slides ordered in two vertical stacks:
 			// 1.1    2.1
 			// 1.2    2.2
 			// 1.3    2.3
 			//
 			// If you're on slide 1.3 and navigate right, you will normally move
 			// from 1.3 -> 2.1. If "grid" is used, the same navigation takes you
 			// from 1.3 -> 2.3.
 			navigationMode: 'default',
 
 			// Randomizes the order of slides each time the presentation loads
 			shuffle: false,
 
 			// Turns fragments on and off globally
 			fragments: true,
 
 			// Flags whether to include the current fragment in the URL,
 			// so that reloading brings you to the same fragment position
 			fragmentInURL: false,
 
 			// 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 question-mark
 			// key is pressed
 			help: true,
 
 			// Flags if it should be possible to pause the presentation (blackout)
 			pause: true,
 
 			// Flags if speaker notes should be visible to all viewers
 			showNotes: false,
 
 			// Global override for autolaying embedded media (video/audio/iframe)
 			// - null:   Media will only autoplay if data-autoplay is present
 			// - true:   All media will autoplay, regardless of individual setting
 			// - false:  No media will autoplay, regardless of individual setting
 			autoPlayMedia: null,
 
 			// Global override for preloading lazy-loaded iframes
 			// - null:   Iframes with data-src AND data-preload will be loaded when within
 			//           the viewDistance, iframes with only data-src will be loaded when visible
 			// - true:   All iframes with data-src will be loaded when within the viewDistance
 			// - false:  All iframes with data-src will be loaded only when visible
 			preloadIframes: null,
 
 			// Controls automatic progression to the next slide
 			// - 0:      Auto-sliding only happens if the data-autoslide HTML attribute
 			//           is present on the current slide or fragment
 			// - 1+:     All slides will progress automatically at the given interval
 			// - false:  No auto-sliding, even if data-autoslide is present
 			autoSlide: 0,
 
 			// Stop auto-sliding after user input
 			autoSlideStoppable: true,
 
 			// Use this method for navigation when auto-sliding (defaults to navigateNext)
 			autoSlideMethod: null,
 
 			// Specify the average time in seconds that you think you will spend
 			// presenting each slide. This is used to show a pacing timer in the
 			// speaker view
 			defaultTiming: null,
 
 			// 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
 			// Add `data-preview-link` and `data-preview-link="false"` to customise each link
 			// individually
 			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 visibility 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"
 
 			// Parallax background repeat
 			parallaxBackgroundRepeat: '', // repeat/repeat-x/repeat-y/no-repeat/initial/inherit
 
 			// Parallax background position
 			parallaxBackgroundPosition: '', // CSS syntax, e.g. "top left"
 
 			// Amount of pixels to move the parallax background per slide step
 			parallaxBackgroundHorizontal: null,
 			parallaxBackgroundVertical: null,
 
 			// The maximum number of pages a single slide can expand onto when printing
 			// to PDF, unlimited by default
 			pdfMaxPagesPerSlide: Number.POSITIVE_INFINITY,
 
 			// Prints each fragment on a separate slide
 			pdfSeparateFragments: true,
 
 			// Offset used to reduce the height of content within exported PDF pages.
 			// This exists to account for environment differences based on how you
 			// print to PDF. CLI printing options, like phantomjs and wkpdf, can end
 			// on precisely the total height of the document whereas in-browser
 			// printing has to end one pixel before.
 			pdfPageHeightOffset: -1,
 
 			// Number of slides away from the current that are visible
 			viewDistance: 3,
 
 			// The display mode that will be used to show slides
 			display: 'block',
 
 			// Hide cursor if inactive
 			hideInactiveCursor: true,
 
 			// Time before the cursor is hidden (in ms)
 			hideCursorTime: 5000,
 
 			// Script dependencies to load
 			dependencies: []
 
 		},
 
 		// Flags if Reveal.initialize() has been called
 		initialized = false,
 
 		// Flags if reveal.js is loaded (has dispatched the 'ready' event)
 		loaded = false,
 
 		// Flags if the overview mode is currently active
 		overview = false,
 
 		// Holds the dimensions of our overview slides, including margins
 		overviewSlideWidth = null,
 		overviewSlideHeight = null,
 
 		// The horizontal and vertical index of the currently active slide
 		indexh,
 		indexv,
 
 		// The previous and current slide HTML elements
 		previousSlide,
 		currentSlide,
 
 		previousBackground,
 
 		// Remember which directions that the user has navigated towards
 		hasNavigatedRight = false,
 		hasNavigatedDown = false,
 
 		// 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 = {},
 
 		// A list of registered reveal.js plugins
 		plugins = {},
 
 		// List of asynchronously loaded reveal.js dependencies
 		asyncDependencies = [],
 
 		// Features supported by the browser, see #checkCapabilities()
 		features = {},
 
 		// Client is a mobile device, see #checkCapabilities()
 		isMobileDevice,
 
 		// Client is a desktop Chrome, see #checkCapabilities()
 		isChrome,
 
 		// Throttles mouse wheel navigation
 		lastMouseWheelStep = 0,
 
 		// Delays updates to the URL due to a Chrome thumbnailer bug
 		writeURLTimeout = 0,
 
 		// Is the mouse pointer currently hidden from view
 		cursorHidden = false,
 
 		// Timeout used to determine when the cursor is inactive
 		cursorInactiveTimeout = 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,
 			startCount: 0,
 			captured: false,
 			threshold: 40
 		},
 
 		// A key:value map of shortcut keyboard keys and descriptions of
 		// the actions they trigger, generated in #configure()
 		keyboardShortcuts = {},
 
 		// Holds custom key code mappings
 		registeredKeyBindings = {};
 
 	/**
 	 * Starts up the presentation if the client is capable.
 	 */
 	function initialize( options ) {
 
 		// Make sure we only initialize once
 		if( initialized === true ) return;
 
 		initialized = true;
 
 		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 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() {
 
 		isMobileDevice = /(iphone|ipod|ipad|android)/gi.test( UA );
 		isChrome = /chrome/i.test( UA ) && !/edge/i.test( UA );
 
 		var testElement = document.createElement( 'div' );
 
 		features.transforms3d = 'WebkitPerspective' in testElement.style ||
 								'MozPerspective' in testElement.style ||
 								'msPerspective' in testElement.style ||
 								'OPerspective' in testElement.style ||
 								'perspective' in testElement.style;
 
 		features.transforms2d = 'WebkitTransform' in testElement.style ||
 								'MozTransform' in testElement.style ||
 								'msTransform' in testElement.style ||
 								'OTransform' in testElement.style ||
 								'transform' in testElement.style;
 
 		features.requestAnimationFrameMethod = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame;
 		features.requestAnimationFrame = typeof features.requestAnimationFrameMethod === 'function';
 
 		features.canvas = !!document.createElement( 'canvas' ).getContext;
 
 		// Transitions in the overview are disabled in desktop and
 		// Safari due to lag
 		features.overviewTransitions = !/Version\/[\d\.]+.*Safari/.test( UA );
 
 		// Flags if we should use zoom instead of transform to scale
 		// up slides. Zoom produces crisper results but has a lot of
 		// xbrowser quirks so we only use it in whitelsited browsers.
 		features.zoom = 'zoom' in testElement.style && !isMobileDevice &&
 						( isChrome || /Version\/[\d\.]+.*Safari/.test( UA ) );
 
 	}
 
 	/**
 	 * 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 = [],
 			scriptsToLoad = 0;
 
 		config.dependencies.forEach( function( s ) {
 			// Load if there's no condition or the condition is truthy
 			if( !s.condition || s.condition() ) {
 				if( s.async ) {
 					asyncDependencies.push( s );
 				}
 				else {
 					scripts.push( s );
 				}
 			}
 		} );
 
 		if( scripts.length ) {
 			scriptsToLoad = scripts.length;
 
 			// Load synchronous scripts
 			scripts.forEach( function( s ) {
 				loadScript( s.src, function() {
 
 					if( typeof s.callback === 'function' ) s.callback();
 
 					if( --scriptsToLoad === 0 ) {
 						initPlugins();
 					}
 
 				} );
 			} );
 		}
 		else {
 			initPlugins();
 		}
 
 	}
 
 	/**
 	 * Initializes our plugins and waits for them to be ready
 	 * before proceeding.
 	 */
 	function initPlugins() {
 
 		var pluginsToInitialize = Object.keys( plugins ).length;
 
 		// If there are no plugins, skip this step
 		if( pluginsToInitialize === 0 ) {
 			loadAsyncDependencies();
 		}
 		// ... otherwise initialize plugins
 		else {
 
 			var afterPlugInitialized = function() {
 				if( --pluginsToInitialize === 0 ) {
 					loadAsyncDependencies();
 				}
 			};
 
 			for( var i in plugins ) {
 
 				var plugin = plugins[i];
 
 				// If the plugin has an 'init' method, invoke it
 				if( typeof plugin.init === 'function' ) {
 					var callback = plugin.init();
 
 					// If the plugin returned a Promise, wait for it
 					if( callback && typeof callback.then === 'function' ) {
 						callback.then( afterPlugInitialized );
 					}
 					else {
 						afterPlugInitialized();
 					}
 				}
 				else {
 					afterPlugInitialized();
 				}
 
 			}
 
 		}
 
 	}
 
 	/**
 	 * Loads all async reveal.js dependencies.
 	 */
 	function loadAsyncDependencies() {
 
 		if( asyncDependencies.length ) {
 			asyncDependencies.forEach( function( s ) {
 				loadScript( s.src, s.callback );
 			} );
 		}
 
 		start();
 
 	}
 
 	/**
 	 * Loads a JavaScript file from the given URL and executes it.
 	 *
 	 * @param {string} url Address of the .js file to load
 	 * @param {function} callback Method to invoke when the script
 	 * has loaded and executed
 	 */
 	function loadScript( url, callback ) {
 
 		var script = document.createElement( 'script' );
 		script.type = 'text/javascript';
 		script.async = false;
 		script.defer = false;
 		script.src = url;
 
 		if( callback ) {
 
 			// Success callback
 			script.onload = script.onreadystatechange = function( event ) {
 				if( event.type === "load" || (/loaded|complete/.test( script.readyState ) ) ) {
 
 					// Kill event listeners
 					script.onload = script.onreadystatechange = script.onerror = null;
 
 					callback();
 
 				}
 			};
 
 			// Error callback
 			script.onerror = function( err ) {
 
 				// Kill event listeners
 				script.onload = script.onreadystatechange = script.onerror = null;
 
 				callback( new Error( 'Failed loading script: ' + script.src + '\n' + err) );
 
 			};
 
 		}
 
 		// Append the script at the end of <head>
 		var head = document.querySelector( 'head' );
 		head.insertBefore( script, head.lastChild );
 
 	}
 
 	/**
 	 * Starts up reveal.js by binding input events and navigating
 	 * to the current URL deeplink if there is one.
 	 */
 	function start() {
 
 		loaded = true;
 
 		// Make sure we've got all the DOM elements we need
 		setupDOM();
 
 		// Listen to messages posted to this window
 		setupPostMessage();
 
 		// Prevent the slides from being scrolled out of view
 		setupScrollPrevention();
 
 		// 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' );
 
 			dom.wrapper.classList.add( 'ready' );
 
 			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' );
 
 		if( isMobileDevice ) {
 			dom.wrapper.classList.add( 'no-hover' );
 		}
 		else {
 			dom.wrapper.classList.remove( 'no-hover' );
 		}
 
 		if( /iphone/gi.test( UA ) ) {
 			dom.wrapper.classList.add( 'ua-iphone' );
 		}
 		else {
 			dom.wrapper.classList.remove( 'ua-iphone' );
 		}
 
 		// 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
 		dom.controls = createSingletonNode( dom.wrapper, 'aside', 'controls',
 			'<button class="navigate-left" aria-label="previous slide"><div class="controls-arrow"></div></button>' +
 			'<button class="navigate-right" aria-label="next slide"><div class="controls-arrow"></div></button>' +
 			'<button class="navigate-up" aria-label="above slide"><div class="controls-arrow"></div></button>' +
 			'<button class="navigate-down" aria-label="below slide"><div class="controls-arrow"></div></button>' );
 
 		// Slide number
 		dom.slideNumber = createSingletonNode( dom.wrapper, 'div', 'slide-number', '' );
 
 		// Element containing notes that are visible to the audience
 		dom.speakerNotes = createSingletonNode( dom.wrapper, 'div', 'speaker-notes', null );
 		dom.speakerNotes.setAttribute( 'data-prevent-swipe', '' );
 		dom.speakerNotes.setAttribute( 'tabindex', '0' );
 
 		// Overlay graphic which is displayed during the paused mode
 		dom.pauseOverlay = createSingletonNode( dom.wrapper, 'div', 'pause-overlay', config.controls ? '<button class="resume-button">Resume presentation</button>' : null );
 
 		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' ) );
 
 		// The right and down arrows in the standard reveal.js controls
 		dom.controlsRightArrow = dom.controls.querySelector( '.navigate-right' );
 		dom.controlsDownArrow = dom.controls.querySelector( '.navigate-down' );
 
 		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.
 	 *
 	 * @return {HTMLElement}
 	 */
 	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;
 
 	}
 
 	/**
 	 * Converts the given HTML element into a string of text
 	 * that can be announced to a screen reader. Hidden
 	 * elements are excluded.
 	 */
 	function getStatusText( node ) {
 
 		var text = '';
 
 		// Text node
 		if( node.nodeType === 3 ) {
 			text += node.textContent;
 		}
 		// Element node
 		else if( node.nodeType === 1 ) {
 
 			var isAriaHidden = node.getAttribute( 'aria-hidden' );
 			var isDisplayHidden = window.getComputedStyle( node )['display'] === 'none';
 			if( isAriaHidden !== 'true' && !isDisplayHidden ) {
 
 				toArray( node.childNodes ).forEach( function( child ) {
 					text += getStatusText( child );
 				} );
 
 			}
 
 		}
 
 		return text;
 
 	}
 
 	/**
 	 * 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: 0px;}' );
 
 		// 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';
 
 		// Make sure stretch elements fit on slide
 		layoutSlideContents( slideWidth, slideHeight );
 
 		// Add each slide's index as attributes on itself, we need these
 		// indices to generate slide numbers below
 		toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( hslide, h ) {
 			hslide.setAttribute( 'data-index-h', h );
 
 			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 );
 				} );
 			}
 		} );
 
 		// 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 = slide.scrollHeight;
 				var numberOfPages = Math.max( Math.ceil( contentHeight / pageHeight ), 1 );
 
 				// Adhere to configured pages per slide limit
 				numberOfPages = Math.min( numberOfPages, config.pdfMaxPagesPerSlide );
 
 				// Center slides vertically
 				if( numberOfPages === 1 && config.center || slide.classList.contains( 'center' ) ) {
 					top = Math.max( ( pageHeight - contentHeight ) / 2, 0 );
 				}
 
 				// Wrap the slide in a page element and hide its overflow
 				// so that no page ever flows onto another
 				var page = document.createElement( 'div' );
 				page.className = 'pdf-page';
 				page.style.height = ( ( pageHeight + config.pdfPageHeightOffset ) * numberOfPages ) + 'px';
 				slide.parentNode.insertBefore( page, slide );
 				page.appendChild( slide );
 
 				// Position the slide inside of the page
 				slide.style.left = left + 'px';
 				slide.style.top = top + 'px';
 				slide.style.width = slideWidth + 'px';
 
 				if( slide.slideBackgroundElement ) {
 					page.insertBefore( slide.slideBackgroundElement, slide );
 				}
 
 				// Inject notes if `showNotes` is enabled
 				if( config.showNotes ) {
 
 					// Are there notes for this slide?
 					var notes = getSlideNotes( slide );
 					if( notes ) {
 
 						var notesSpacing = 8;
 						var notesLayout = typeof config.showNotes === 'string' ? config.showNotes : 'inline';
 						var notesElement = document.createElement( 'div' );
 						notesElement.classList.add( 'speaker-notes' );
 						notesElement.classList.add( 'speaker-notes-pdf' );
 						notesElement.setAttribute( 'data-layout', notesLayout );
 						notesElement.innerHTML = notes;
 
 						if( notesLayout === 'separate-page' ) {
 							page.parentNode.insertBefore( notesElement, page.nextSibling );
 						}
 						else {
 							notesElement.style.left = notesSpacing + 'px';
 							notesElement.style.bottom = notesSpacing + 'px';
 							notesElement.style.width = ( pageWidth - notesSpacing*2 ) + 'px';
 							page.appendChild( notesElement );
 						}
 
 					}
 
 				}
 
 				// Inject slide numbers if `slideNumbers` are enabled
 				if( config.slideNumber && /all|print/i.test( config.showSlideNumber ) ) {
 					var slideNumberH = parseInt( slide.getAttribute( 'data-index-h' ), 10 ) + 1,
 						slideNumberV = parseInt( slide.getAttribute( 'data-index-v' ), 10 ) + 1;
 
 					var numberElement = document.createElement( 'div' );
 					numberElement.classList.add( 'slide-number' );
 					numberElement.classList.add( 'slide-number-pdf' );
 					numberElement.innerHTML = formatSlideNumber( slideNumberH, '.', slideNumberV );
 					page.appendChild( numberElement );
 				}
 
 				// Copy page and show fragments one after another
 				if( config.pdfSeparateFragments ) {
 
 					// Each fragment 'group' is an array containing one or more
 					// fragments. Multiple fragments that appear at the same time
 					// are part of the same group.
 					var fragmentGroups = sortFragments( page.querySelectorAll( '.fragment' ), true );
 
 					var previousFragmentStep;
 					var previousPage;
 
 					fragmentGroups.forEach( function( fragments ) {
 
 						// Remove 'current-fragment' from the previous group
 						if( previousFragmentStep ) {
 							previousFragmentStep.forEach( function( fragment ) {
 								fragment.classList.remove( 'current-fragment' );
 							} );
 						}
 
 						// Show the fragments for the current index
 						fragments.forEach( function( fragment ) {
 							fragment.classList.add( 'visible', 'current-fragment' );
 						} );
 
 						// Create a separate page for the current fragment state
 						var clonedPage = page.cloneNode( true );
 						page.parentNode.insertBefore( clonedPage, ( previousPage || page ).nextSibling );
 
 						previousFragmentStep = fragments;
 						previousPage = clonedPage;
 
 					} );
 
 					// Reset the first/original page so that all fragments are hidden
 					fragmentGroups.forEach( function( fragments ) {
 						fragments.forEach( function( fragment ) {
 							fragment.classList.remove( 'visible', 'current-fragment' );
 						} );
 					} );
 
 				}
 				// Show all fragments
 				else {
 					toArray( page.querySelectorAll( '.fragment:not(.fade-out)' ) ).forEach( function( fragment ) {
 						fragment.classList.add( 'visible' );
 					} );
 				}
 
 			}
 
 		} );
 
 		// Notify subscribers that the PDF layout is good to go
 		dispatchEvent( 'pdf-ready' );
 
 	}
 
 	/**
 	 * This is an unfortunate necessity. Some actions – such as
 	 * an input field being focused in an iframe or using the
 	 * keyboard to expand text selection beyond the bounds of
 	 * a slide – can trigger our content to be pushed out of view.
 	 * This scrolling can not be prevented by hiding overflow in
 	 * CSS (we already do) so we have to resort to repeatedly
 	 * checking if the slides have been offset :(
 	 */
 	function setupScrollPrevention() {
 
 		setInterval( function() {
 			if( dom.wrapper.scrollTop !== 0 || dom.wrapper.scrollLeft !== 0 ) {
 				dom.wrapper.scrollTop = 0;
 				dom.wrapper.scrollLeft = 0;
 			}
 		}, 1000 );
 
 	}
 
 	/**
 	 * Creates an HTML element and returns a reference to it.
 	 * If the element already exists the existing instance will
 	 * be returned.
 	 *
 	 * @param {HTMLElement} container
 	 * @param {string} tagname
 	 * @param {string} classname
 	 * @param {string} innerHTML
 	 *
 	 * @return {HTMLElement}
 	 */
 	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.className = 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 = createBackground( slideh, dom.background );
 
 			// Iterate over all vertical slides
 			toArray( slideh.querySelectorAll( 'section' ) ).forEach( function( slidev ) {
 
 				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;
 			dom.background.style.backgroundRepeat = config.parallaxBackgroundRepeat;
 			dom.background.style.backgroundPosition = config.parallaxBackgroundPosition;
 
 			// 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
 	 * @return {HTMLElement} New background div
 	 */
 	function createBackground( slide, container ) {
 
 
 		// Main slide background element
 		var element = document.createElement( 'div' );
 		element.className = 'slide-background ' + slide.className.replace( /present|past|future/, '' );
 
 		// Inner background element that wraps images/videos/iframes
 		var contentElement = document.createElement( 'div' );
 		contentElement.className = 'slide-background-content';
 
 		element.appendChild( contentElement );
 		container.appendChild( element );
 
 		slide.slideBackgroundElement = element;
 		slide.slideBackgroundContentElement = contentElement;
 
 		// Syncs the background to reflect all current background settings
 		syncBackground( slide );
 
 		return element;
 
 	}
 
 	/**
 	 * Renders all of the visual properties of a slide background
 	 * based on the various background attributes.
 	 *
 	 * @param {HTMLElement} slide
 	 */
 	function syncBackground( slide ) {
 
 		var element = slide.slideBackgroundElement,
 			contentElement = slide.slideBackgroundContentElement;
 
 		// Reset the prior background state in case this is not the
 		// initial sync
 		slide.classList.remove( 'has-dark-background' );
 		slide.classList.remove( 'has-light-background' );
 
 		element.removeAttribute( 'data-loaded' );
 		element.removeAttribute( 'data-background-hash' );
 		element.removeAttribute( 'data-background-size' );
 		element.removeAttribute( 'data-background-transition' );
 		element.style.backgroundColor = '';
 
 		contentElement.style.backgroundSize = '';
 		contentElement.style.backgroundRepeat = '';
 		contentElement.style.backgroundPosition = '';
 		contentElement.style.backgroundImage = '';
 		contentElement.style.opacity = '';
 		contentElement.innerHTML = '';
 
 		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' ),
 			backgroundOpacity: slide.getAttribute( 'data-background-opacity' )
 		};
 
 		if( data.background ) {
 			// Auto-wrap image urls in url(...)
 			if( /^(http|file|\/\/)/gi.test( data.background ) || /\.(svg|png|jpg|jpeg|gif|bmp)([?#\s]|$)/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 +
 															data.backgroundOpacity );
 		}
 
 		// Additional and optional background properties
 		if( data.backgroundSize ) element.setAttribute( 'data-background-size', data.backgroundSize );
 		if( data.backgroundColor ) element.style.backgroundColor = data.backgroundColor;
 		if( data.backgroundTransition ) element.setAttribute( 'data-background-transition', data.backgroundTransition );
 
 		// Background image options are set on the content wrapper
 		if( data.backgroundSize ) contentElement.style.backgroundSize = data.backgroundSize;
 		if( data.backgroundRepeat ) contentElement.style.backgroundRepeat = data.backgroundRepeat;
 		if( data.backgroundPosition ) contentElement.style.backgroundPosition = data.backgroundPosition;
 		if( data.backgroundOpacity ) contentElement.style.opacity = data.backgroundOpacity;
 
 		// If this slide has a background color, we add a class that
 		// signals if it is light or dark. If the slide has no background
 		// color, no class will be added
 		var contrastColor = data.backgroundColor;
 
 		// If no bg color was found, check the computed background
 		if( !contrastColor ) {
 			var computedBackgroundStyle = window.getComputedStyle( element );
 			if( computedBackgroundStyle && computedBackgroundStyle.backgroundColor ) {
 				contrastColor = computedBackgroundStyle.backgroundColor;
 			}
 		}
 
 		if( contrastColor ) {
 			var rgb = colorToRgb( contrastColor );
 
 			// 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( contrastColor ) < 128 ) {
 					slide.classList.add( 'has-dark-background' );
 				}
 				else {
 					slide.classList.add( 'has-light-background' );
 				}
 			}
 		}
 
 	}
 
 	/**
 	 * 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.
 	 *
 	 * @param {object} options
 	 */
 	function configure( options ) {
 
 		var oldTransition = 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 );
 
 		// Abort if reveal.js hasn't finished loading, config
 		// changes will be applied automatically once loading
 		// finishes
 		if( loaded === false ) return;
 
 		var numberOfSlides = dom.wrapper.querySelectorAll( SLIDES_SELECTOR ).length;
 
 		// Remove the previously configured transition class
 		dom.wrapper.classList.remove( oldTransition );
 
 		// 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';
 
 		dom.controls.setAttribute( 'data-controls-layout', config.controlsLayout );
 		dom.controls.setAttribute( 'data-controls-back-arrows', config.controlsBackArrows );
 
 		if( config.shuffle ) {
 			shuffle();
 		}
 
 		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.showNotes ) {
 			dom.speakerNotes.setAttribute( 'data-layout', typeof config.showNotes === 'string' ? config.showNotes : 'inline' );
 		}
 
 		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();
 		}
 
 		// Auto-hide the mouse pointer when its inactive
 		if( config.hideInactiveCursor ) {
 			document.addEventListener( 'mousemove', onDocumentCursorActive, false );
 			document.addEventListener( 'mousedown', onDocumentCursorActive, false );
 		}
 		else {
 			showCursor();
 
 			document.removeEventListener( 'mousemove', onDocumentCursorActive, false );
 			document.removeEventListener( 'mousedown', onDocumentCursorActive, false );
 		}
 
 		// Iframe link previews
 		if( config.previewLinks ) {
 			enablePreviewLinks();
 			disablePreviewLinks( '[data-preview-link=false]' );
 		}
 		else {
 			disablePreviewLinks();
 			enablePreviewLinks( '[data-preview-link]:not([data-preview-link=false])' );
 		}
 
 		// 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' );
 			} );
 		}
 
 		// Slide numbers
 		var slideNumberDisplay = 'none';
 		if( config.slideNumber && !isPrintingPDF() ) {
 			if( config.showSlideNumber === 'all' ) {
 				slideNumberDisplay = 'block';
 			}
 			else if( config.showSlideNumber === 'speaker' && isSpeakerNotes() ) {
 				slideNumberDisplay = 'block';
 			}
 		}
 
 		dom.slideNumber.style.display = slideNumberDisplay;
 
 		// Add the navigation mode to the DOM so we can adjust styling
 		if( config.navigationMode !== 'default' ) {
 			dom.wrapper.setAttribute( 'data-navigation-mode', config.navigationMode );
 		}
 		else {
 			dom.wrapper.removeAttribute( 'data-navigation-mode' );
 		}
 
 		// Define our contextual list of keyboard shortcuts
 		if( config.navigationMode === 'linear' ) {
 			keyboardShortcuts['&#8594;  ,  &#8595;  ,  SPACE  ,  N  ,  L  ,  J'] = 'Next slide';
 			keyboardShortcuts['&#8592;  ,  &#8593;  ,  P  ,  H  ,  K']           = 'Previous slide';
 		}
 		else {
 			keyboardShortcuts['N  ,  SPACE']   = 'Next slide';
 			keyboardShortcuts['P']             = 'Previous slide';
 			keyboardShortcuts['&#8592;  ,  H'] = 'Navigate left';
 			keyboardShortcuts['&#8594;  ,  L'] = 'Navigate right';
 			keyboardShortcuts['&#8593;  ,  K'] = 'Navigate up';
 			keyboardShortcuts['&#8595;  ,  J'] = 'Navigate down';
 		}
 
 		keyboardShortcuts['Home  ,  &#8984;/CTRL &#8592;'] = 'First slide';
 		keyboardShortcuts['End  ,  &#8984;/CTRL &#8594;']  = 'Last slide';
 		keyboardShortcuts['B  ,  .']                       = 'Pause';
 		keyboardShortcuts['F']                             = 'Fullscreen';
 		keyboardShortcuts['ESC, O']                        = 'Slide overview';
 
 		sync();
 
 	}
 
 	/**
 	 * Binds all event listeners.
 	 */
 	function addEventListeners() {
 
 		eventsAreBound = true;
 
 		window.addEventListener( 'hashchange', onWindowHashChange, false );
 		window.addEventListener( 'resize', onWindowResize, false );
 
 		if( config.touch ) {
 			if( 'onpointerdown' in window ) {
 				// Use W3C 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 );
 			}
 			else {
 				// Fall back to touch events
 				dom.wrapper.addEventListener( 'touchstart', onTouchStart, false );
 				dom.wrapper.addEventListener( 'touchmove', onTouchMove, false );
 				dom.wrapper.addEventListener( 'touchend', onTouchEnd, 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 );
 		}
 
 		dom.pauseOverlay.addEventListener( 'click', resume, 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( UA.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( 'pointerdown', onPointerDown, false );
 		dom.wrapper.removeEventListener( 'pointermove', onPointerMove, false );
 		dom.wrapper.removeEventListener( 'pointerup', onPointerUp, false );
 
 		dom.wrapper.removeEventListener( 'MSPointerDown', onPointerDown, false );
 		dom.wrapper.removeEventListener( 'MSPointerMove', onPointerMove, false );
 		dom.wrapper.removeEventListener( 'MSPointerUp', onPointerUp, false );
 
 		dom.wrapper.removeEventListener( 'touchstart', onTouchStart, false );
 		dom.wrapper.removeEventListener( 'touchmove', onTouchMove, false );
 		dom.wrapper.removeEventListener( 'touchend', onTouchEnd, false );
 
 		dom.pauseOverlay.removeEventListener( 'click', resume, 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 ); } );
 		} );
 
 	}
 
 	/**
 	 * Registers a new plugin with this reveal.js instance.
 	 *
 	 * reveal.js waits for all regisered plugins to initialize
 	 * before considering itself ready, as long as the plugin
 	 * is registered before calling `Reveal.initialize()`.
 	 */
 	function registerPlugin( id, plugin ) {
 
 		if( plugins[id] === undefined ) {
 			plugins[id] = plugin;
 
 			// If a plugin is registered after reveal.js is loaded,
 			// initialize it right away
 			if( loaded && typeof plugin.init === 'function' ) {
 				plugin.init();
 			}
 		}
 		else {
 			console.warn( 'reveal.js: "'+ id +'" plugin has already been registered' );
 		}
 
 	}
 
 	/**
 	 * Checks if a specific plugin has been registered.
 	 *
 	 * @param {String} id Unique plugin identifier
 	 */
 	function hasPlugin( id ) {
 
 		return !!plugins[id];
 
 	}
 
 	/**
 	 * Returns the specific plugin instance, if a plugin
 	 * with the given ID has been registered.
 	 *
 	 * @param {String} id Unique plugin identifier
 	 */
 	function getPlugin( id ) {
 
 		return plugins[id];
 
 	}
 
 	/**
 	 * Add a custom key binding with optional description to
 	 * be added to the help screen.
 	 */
 	function addKeyBinding( binding, callback ) {
 
 		if( typeof binding === 'object' && binding.keyCode ) {
 			registeredKeyBindings[binding.keyCode] = {
 				callback: callback,
 				key: binding.key,
 				description: binding.description
 			};
 		}
 		else {
 			registeredKeyBindings[binding] = {
 				callback: callback,
 				key: null,
 				description: null
 			};
 		}
 
 	}
 
 	/**
 	 * Removes the specified custom key binding.
 	 */
 	function removeKeyBinding( keyCode ) {
 
 		delete registeredKeyBindings[keyCode];
 
 	}
 
 	/**
 	 * Extend object a with the properties of object b.
 	 * If there's a conflict, object b takes precedence.
 	 *
 	 * @param {object} a
 	 * @param {object} b
 	 */
 	function extend( a, b ) {
 
 		for( var i in b ) {
 			a[ i ] = b[ i ];
 		}
 
 		return a;
 
 	}
 
 	/**
 	 * Converts the target object to an array.
 	 *
 	 * @param {object} o
 	 * @return {object[]}
 	 */
 	function toArray( o ) {
 
 		return Array.prototype.slice.call( o );
 
 	}
 
 	/**
 	 * Utility for deserializing a value.
 	 *
 	 * @param {*} value
 	 * @return {*}
 	 */
 	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
 	 *
 	 * @return {number}
 	 */
 	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.
 	 *
 	 * @param {HTMLElement} element
 	 * @param {string} transform
 	 */
 	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.
 	 *
 	 * @param {object} transforms
 	 */
 	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.
 	 *
 	 * @param {string} value
 	 */
 	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 );
 
 	}
 
 	/**
 	 * Find the closest parent that matches the given
 	 * selector.
 	 *
 	 * @param {HTMLElement} target The child element
 	 * @param {String} selector The CSS selector to match
 	 * the parents against
 	 *
 	 * @return {HTMLElement} The matched parent or null
 	 * if no matching parent was found
 	 */
 	function closestParent( target, selector ) {
 
 		var parent = target.parentNode;
 
 		while( parent ) {
 
 			// There's some overhead doing this each time, we don't
 			// want to rewrite the element prototype but should still
 			// be enough to feature detect once at startup...
 			var matchesMethod = parent.matches || parent.matchesSelector || parent.msMatchesSelector;
 
 			// If we find a match, we're all set
 			if( matchesMethod && matchesMethod.call( parent, selector ) ) {
 				return parent;
 			}
 
 			// Keep searching
 			parent = parent.parentNode;
 
 		}
 
 		return null;
 
 	}
 
 	/**
 	 * Converts various color input formats to an {r:0,g:0,b:0} object.
 	 *
 	 * @param {string} color The string representation of a color
 	 * @example
 	 * colorToRgb('#000');
 	 * @example
 	 * colorToRgb('#000000');
 	 * @example
 	 * colorToRgb('rgb(0,0,0)');
 	 * @example
 	 * colorToRgb('rgba(0,0,0)');
 	 *
 	 * @return {{r: number, g: number, b: number, [a]: number}|null}
 	 */
 	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 {string} color See colorToRgb for supported formats.
 	 * @see {@link colorToRgb}
 	 */
 	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;
 
 	}
 
 	/**
 	 * Returns the remaining height within the parent of the
 	 * target element.
 	 *
 	 * remaining height = [ configured parent height ] - [ current parent height ]
 	 *
 	 * @param {HTMLElement} element
 	 * @param {number} [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';
 
 			// In Overview mode, the parent (.slide) height is set of 700px.
 			// Restore it temporarily to its natural height.
 			element.parentNode.style.height = 'auto';
 
 			newHeight = height - element.parentNode.offsetHeight;
 
 			// Restore the old height, just in case
 			element.style.height = oldHeight + 'px';
 
 			// Clear the parent (.slide) height. .removeProperty works in IE9+
 			element.parentNode.style.removeProperty('height');
 
 			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.
 	 *
 	 * @param {string} [selector=a] - selector for anchors
 	 */
 	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( selector ) {
 
 		var anchors = toArray( document.querySelectorAll( selector ? selector : '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.
 	 *
 	 * @param {string} url - url for preview iframe src
 	 */
 	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>',
 				'<small class="viewport-inner">',
 					'<span class="x-frame-error">Unable to load iframe. This is likely due to the site\'s policy (x-frame-options).</span>',
 				'</small>',
 			'</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 );
 
 	}
 
 	/**
 	 * Open or close help overlay window.
 	 *
 	 * @param {Boolean} [override] Flag which overrides the
 	 * toggle logic and forcibly sets the desired state. True means
 	 * help is open, false means it's closed.
 	 */
 	function toggleHelp( override ){
 
 		if( typeof override === 'boolean' ) {
 			override ? showHelp() : closeOverlay();
 		}
 		else {
 			if( dom.overlay ) {
 				closeOverlay();
 			}
 			else {
 				showHelp();
 			}
 		}
 	}
 
 	/**
 	 * Opens an 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>';
 			}
 
 			// Add custom key bindings that have associated descriptions
 			for( var binding in registeredKeyBindings ) {
 				if( registeredKeyBindings[binding].key && registeredKeyBindings[binding].description ) {
 					html += '<tr><td>' + registeredKeyBindings[binding].key + '</td><td>' + registeredKeyBindings[binding].description + '</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() ) {
 
 			if( !config.disableLayout ) {
 
 				// On some mobile devices '100vh' is taller than the visible
 				// viewport which leads to part of the presentation being
 				// cut off. To work around this we define our own '--vh' custom
 				// property where 100x adds up to the correct height.
 				//
 				// https://css-tricks.com/the-trick-to-viewport-units-on-mobile/
 				if( isMobileDevice ) {
 					document.documentElement.style.setProperty( '--vh', ( window.innerHeight * 0.01 ) + 'px' );
 				}
 
 				var size = getComputedSlideSize();
 
 				var oldScale = scale;
 
 				// Layout the contents of the slides
 				layoutSlideContents( config.width, config.height );
 
 				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 zoom for scaling up so that content remains crisp.
 					// Don't use zoom to scale down since that can lead to shifts
 					// in text layout/line breaks.
 					if( scale > 1 && features.zoom ) {
 						dom.slides.style.zoom = scale;
 						dom.slides.style.left = '';
 						dom.slides.style.top = '';
 						dom.slides.style.bottom = '';
 						dom.slides.style.right = '';
 						transformSlides( { layout: '' } );
 					}
 					// Apply scale transform as a fallback
 					else {
 						dom.slides.style.zoom = '';
 						dom.slides.style.left = '50%';
 						dom.slides.style.top = '50%';
 						dom.slides.style.bottom = 'auto';
 						dom.slides.style.right = 'auto';
 						transformSlides( { layout: 'translate(-50%, -50%) scale('+ scale +')' } );
 					}
 				}
 
 				// 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 - slide.scrollHeight ) / 2, 0 ) + 'px';
 						}
 					}
 					else {
 						slide.style.top = '';
 					}
 
 				}
 
 				if( oldScale !== scale ) {
 					dispatchEvent( 'resize', {
 						'oldScale': oldScale,
 						'scale': scale,
 						'size': size
 					} );
 				}
 			}
 
 			updateProgress();
 			updateParallax();
 
 			if( isOverview() ) {
 				updateOverview();
 			}
 
 		}
 
 	}
 
 	/**
 	 * Applies layout logic to the contents of all slides in
 	 * the presentation.
 	 *
 	 * @param {string|number} width
 	 * @param {string|number} height
 	 */
 	function layoutSlideContents( width, height ) {
 
 		// 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.
 	 *
 	 * @param {number} [presentationWidth=dom.wrapper.offsetWidth]
 	 * @param {number} [presentationHeight=dom.wrapper.offsetHeight]
 	 */
 	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 {string|number} [v=0] 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 );
 				}
 			} );
 
 			// Calculate slide sizes
 			var margin = 70;
 			var slideSize = getComputedSlideSize();
 			overviewSlideWidth = slideSize.width + margin;
 			overviewSlideHeight = slideSize.height + margin;
 
 			// Reverse in RTL mode
 			if( config.rtl ) {
 				overviewSlideWidth = -overviewSlideWidth;
 			}
 
 			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() {
 
 		// Layout slides
 		toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( hslide, h ) {
 			hslide.setAttribute( 'data-index-h', h );
 			transformElement( hslide, 'translate3d(' + ( h * overviewSlideWidth ) + '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 * overviewSlideHeight ) + 'px, 0)' );
 				} );
 
 			}
 		} );
 
 		// Layout slide backgrounds
 		toArray( dom.background.childNodes ).forEach( function( hbackground, h ) {
 			transformElement( hbackground, 'translate3d(' + ( h * overviewSlideWidth ) + 'px, 0, 0)' );
 
 			toArray( hbackground.querySelectorAll( '.slide-background' ) ).forEach( function( vbackground, v ) {
 				transformElement( vbackground, 'translate3d(0, ' + ( v * overviewSlideHeight ) + 'px, 0)' );
 			} );
 		} );
 
 	}
 
 	/**
 	 * Moves the overview viewport to the current slides.
 	 * Called each time the current slide changes.
 	 */
 	function updateOverview() {
 
 		var vmin = Math.min( window.innerWidth, window.innerHeight );
 		var scale = Math.max( vmin / 5, 150 ) / vmin;
 
 		transformSlides( {
 			overview: [
 				'scale('+ scale +')',
 				'translateX('+ ( -indexh * overviewSlideWidth ) +'px)',
 				'translateY('+ ( -indexv * overviewSlideHeight ) +'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] 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;
 
 	}
 
 	/**
 	 * Return a hash URL that will resolve to the current slide location.
 	 */
 	function locationHash() {
 
 		var url = '/';
 
 		// Attempt to create a named link based on the slide's ID
 		var id = currentSlide ? currentSlide.getAttribute( 'id' ) : null;
 		if( id ) {
 			id = encodeURIComponent( id );
 		}
 
 		var indexf;
 		if( config.fragmentInURL ) {
 			indexf = getIndices().f;
 		}
 
 		// If the current slide has an ID, use that as a named link,
 		// but we don't support named links with a fragment index
 		if( typeof id === 'string' && id.length && indexf === undefined ) {
 			url = '/' + id;
 		}
 		// Otherwise use the /h/v index
 		else {
 			var hashIndexBase = config.hashOneBasedIndex ? 1 : 0;
 			if( indexh > 0 || indexv > 0 || indexf !== undefined ) url += indexh + hashIndexBase;
 			if( indexv > 0 || indexf !== undefined ) url += '/' + (indexv + hashIndexBase );
 			if( indexf !== undefined ) url += '/' + indexf;
 		}
 
 		return url;
 
 	}
 
 	/**
 	 * Checks if the current or specified slide is vertical
 	 * (nested within another slide).
 	 *
 	 * @param {HTMLElement} [slide=currentSlide] The slide to check
 	 * orientation of
 	 * @return {Boolean}
 	 */
 	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.documentElement;
 
 		// Check which implementation is available
 		var requestMethod = element.requestFullscreen ||
 							element.webkitRequestFullscreen ||
 							element.webkitRequestFullScreen ||
 							element.mozRequestFullScreen ||
 							element.msRequestFullscreen;
 
 		if( requestMethod ) {
 			requestMethod.apply( element );
 		}
 
 	}
 
 	/**
 	 * Shows the mouse pointer after it has been hidden with
 	 * #hideCursor.
 	 */
 	function showCursor() {
 
 		if( cursorHidden ) {
 			cursorHidden = false;
 			dom.wrapper.style.cursor = '';
 		}
 
 	}
 
 	/**
 	 * Hides the mouse pointer when it's on top of the .reveal
 	 * container.
 	 */
 	function hideCursor() {
 
 		if( cursorHidden === false ) {
 			cursorHidden = true;
 			dom.wrapper.style.cursor = 'none';
 		}
 
 	}
 
 	/**
 	 * 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.
 	 *
 	 * @return {Boolean}
 	 */
 	function isPaused() {
 
 		return dom.wrapper.classList.contains( 'paused' );
 
 	}
 
 	/**
 	 * Toggles the auto slide mode on and off.
 	 *
 	 * @param {Boolean} [override] 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.
 	 *
 	 * @return {Boolean}
 	 */
 	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 {number} [h=indexh] Horizontal index of the target slide
 	 * @param {number} [v=indexv] Vertical index of the target slide
 	 * @param {number} [f] Index of a fragment within the
 	 * target slide to activate
 	 * @param {number} [o] 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 );
 
 		// Abort if there are no slides
 		if( horizontalSlides.length === 0 ) return;
 
 		// 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();
 
 		// 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) {
 			// 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 !== currentSlide ) {
 			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 );
 			}
 		}
 
 		// 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() );
 		}
 
 		if( slideChanged ) {
 			dispatchEvent( 'slidechanged', {
 				'indexh': indexh,
 				'indexv': indexv,
 				'previousSlide': previousSlide,
 				'currentSlide': currentSlide,
 				'origin': o
 			} );
 		}
 
 		// Handle embedded content
 		if( slideChanged || !previousSlide ) {
 			stopEmbeddedContent( previousSlide );
 			startEmbeddedContent( currentSlide );
 		}
 
 		// Announce the current slide contents, for screen readers
 		dom.statusDiv.textContent = getStatusText( currentSlide );
 
 		updateControls();
 		updateProgress();
 		updateBackground();
 		updateParallax();
 		updateSlideNumber();
 		updateNotes();
 		updateFragments();
 
 		// 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();
 		updateSlideNumber();
 		updateSlidesVisibility();
 		updateBackground( true );
 		updateNotesVisibility();
 		updateNotes();
 
 		formatEmbeddedContent();
 
 		// Start or stop embedded content depending on global config
 		if( config.autoPlayMedia === false ) {
 			stopEmbeddedContent( currentSlide, { unloadIframes: false } );
 		}
 		else {
 			startEmbeddedContent( currentSlide );
 		}
 
 		if( isOverview() ) {
 			layoutOverview();
 		}
 
 	}
 
 	/**
 	 * Updates reveal.js to keep in sync with new slide attributes. For
 	 * example, if you add a new `data-background-image` you can call
 	 * this to have reveal.js render the new background image.
 	 *
 	 * Similar to #sync() but more efficient when you only need to
 	 * refresh a specific slide.
 	 *
 	 * @param {HTMLElement} slide
 	 */
 	function syncSlide( slide ) {
 
 		// Default to the current slide
 		slide = slide || currentSlide;
 
 		syncBackground( slide );
 		syncFragments( slide );
 
 		updateBackground();
 		updateNotes();
 
 		loadSlide( slide );
 
 	}
 
 	/**
 	 * Formats the fragments on the given slide so that they have
 	 * valid indices. Call this if fragments are changed in the DOM
 	 * after reveal.js has already initialized.
 	 *
 	 * @param {HTMLElement} slide
 	 * @return {Array} a list of the HTML fragments that were synced
 	 */
 	function syncFragments( slide ) {
 
 		// Default to the current slide
 		slide = slide || currentSlide;
 
 		return sortFragments( slide.querySelectorAll( '.fragment' ) );
 
 	}
 
 	/**
 	 * 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' ) );
 
 		} );
 
 	}
 
 	/**
 	 * Randomly shuffles all slides in the deck.
 	 */
 	function shuffle() {
 
 		var slides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
 
 		slides.forEach( function( slide ) {
 
 			// Insert this slide next to another random slide. This may
 			// cause the slide to insert before itself but that's fine.
 			dom.slides.insertBefore( slide, slides[ Math.floor( Math.random() * slides.length ) ] );
 
 		} );
 
 	}
 
 	/**
 	 * 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 ) {
 						// Show all fragments in prior slides
 						toArray( element.querySelectorAll( '.fragment' ) ).forEach( function( fragment ) {
 							fragment.classList.add( 'visible' );
 							fragment.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 ) {
 						// Hide all fragments in future slides
 						toArray( element.querySelectorAll( '.fragment.visible' ) ).forEach( function( fragment ) {
 							fragment.classList.remove( 'visible' );
 							fragment.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 ) {
 					loadSlide( horizontalSlide );
 				}
 				else {
 					unloadSlide( 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 ) {
 							loadSlide( verticalSlide );
 						}
 						else {
 							unloadSlide( verticalSlide );
 						}
 					}
 
 				}
 			}
 
 			// Flag if there are ANY vertical slides, anywhere in the deck
 			if( dom.wrapper.querySelectorAll( '.slides>section>section' ).length ) {
 				dom.wrapper.classList.add( 'has-vertical-slides' );
 			}
 			else {
 				dom.wrapper.classList.remove( 'has-vertical-slides' );
 			}
 
 			// Flag if there are ANY horizontal slides, anywhere in the deck
 			if( dom.wrapper.querySelectorAll( '.slides>section' ).length > 1 ) {
 				dom.wrapper.classList.add( 'has-horizontal-slides' );
 			}
 			else {
 				dom.wrapper.classList.remove( 'has-horizontal-slides' );
 			}
 
 		}
 
 	}
 
 	/**
 	 * Pick up notes from the current slide and display them
 	 * to the viewer.
 	 *
 	 * @see {@link config.showNotes}
 	 */
 	function updateNotes() {
 
 		if( config.showNotes && dom.speakerNotes && currentSlide && !isPrintingPDF() ) {
 
 			dom.speakerNotes.innerHTML = getSlideNotes() || '<span class="notes-placeholder">No notes on this slide.</span>';
 
 		}
 
 	}
 
 	/**
 	 * Updates the visibility of the speaker notes sidebar that
 	 * is used to share annotated slides. The notes sidebar is
 	 * only visible if showNotes is true and there are notes on
 	 * one or more slides in the deck.
 	 */
 	function updateNotesVisibility() {
 
 		if( config.showNotes && hasNotes() ) {
 			dom.wrapper.classList.add( 'show-notes' );
 		}
 		else {
 			dom.wrapper.classList.remove( 'show-notes' );
 		}
 
 	}
 
 	/**
 	 * Checks if there are speaker notes for ANY slide in the
 	 * presentation.
 	 */
 	function hasNotes() {
 
 		return dom.slides.querySelectorAll( '[data-notes], aside.notes' ).length > 0;
 
 	}
 
 	/**
 	 * 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 to match the current slide.
 	 */
 	function updateSlideNumber() {
 
 		// Update slide number if enabled
 		if( config.slideNumber && dom.slideNumber ) {
 
 			var value;
 			var format = 'h.v';
 
 			if( typeof config.slideNumber === 'function' ) {
 				value = config.slideNumber();
 			}
 			else {
 				// Check if a custom number format is available
 				if( typeof config.slideNumber === 'string' ) {
 					format = config.slideNumber;
 				}
 
 				// If there are ONLY vertical slides in this deck, always use
 				// a flattened slide number
 				if( !/c/.test( format ) && dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ).length === 1 ) {
 					format = 'c';
 				}
 
 				value = [];
 				switch( format ) {
 					case 'c':
 						value.push( getSlidePastCount() + 1 );
 						break;
 					case 'c/t':
 						value.push( getSlidePastCount() + 1, '/', getTotalSlides() );
 						break;
 					case 'h/v':
 						value.push( indexh + 1 );
 						if( isVerticalSlide() ) value.push( '/', indexv + 1 );
 						break;
 					default:
 						value.push( indexh + 1 );
 						if( isVerticalSlide() ) value.push( '.', indexv + 1 );
 				}
 			}
 
 			dom.slideNumber.innerHTML = formatSlideNumber( value[0], value[1], value[2] );
 		}
 
 	}
 
 	/**
 	 * Applies HTML formatting to a slide number before it's
 	 * written to the DOM.
 	 *
 	 * @param {number} a Current slide
 	 * @param {string} delimiter Character to separate slide numbers
 	 * @param {(number|*)} b Total slides
 	 * @return {string} HTML string fragment
 	 */
 	function formatSlideNumber( a, delimiter, b ) {
 
 		var url = '#' + locationHash();
 		if( typeof b === 'number' && !isNaN( b ) ) {
 			return  '<a href="' + url + '">' +
 					'<span class="slide-number-a">'+ a +'</span>' +
 					'<span class="slide-number-delimiter">'+ delimiter +'</span>' +
 					'<span class="slide-number-b">'+ b +'</span>' +
 					'</a>';
 		}
 		else {
 			return '<a href="' + url + '">' +
 			       '<span class="slide-number-a">'+ a +'</span>' +
 			       '</a>';
 		}
 
 	}
 
 	/**
 	 * 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' );
 
 			// Set 'disabled' attribute on all directions
 			node.setAttribute( 'disabled', 'disabled' );
 		} );
 
 		// Add the 'enabled' class to the available routes; remove 'disabled' attribute to enable buttons
 		if( routes.left ) dom.controlsLeft.forEach( function( el ) { el.classList.add( 'enabled' ); el.removeAttribute( 'disabled' ); } );
 		if( routes.right ) dom.controlsRight.forEach( function( el ) { el.classList.add( 'enabled' ); el.removeAttribute( 'disabled' ); } );
 		if( routes.up ) dom.controlsUp.forEach( function( el ) { el.classList.add( 'enabled' ); el.removeAttribute( 'disabled' ); } );
 		if( routes.down ) dom.controlsDown.forEach( function( el ) { el.classList.add( 'enabled' ); el.removeAttribute( 'disabled' ); } );
 
 		// Prev/next buttons
 		if( routes.left || routes.up ) dom.controlsPrev.forEach( function( el ) { el.classList.add( 'enabled' ); el.removeAttribute( 'disabled' ); } );
 		if( routes.right || routes.down ) dom.controlsNext.forEach( function( el ) { el.classList.add( 'enabled' ); el.removeAttribute( 'disabled' ); } );
 
 		// 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' ); el.removeAttribute( 'disabled' ); } );
 			if( fragments.next ) dom.controlsNext.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); el.removeAttribute( 'disabled' ); } );
 
 			// 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' ); el.removeAttribute( 'disabled' ); } );
 				if( fragments.next ) dom.controlsDown.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); el.removeAttribute( 'disabled' ); } );
 			}
 			else {
 				if( fragments.prev ) dom.controlsLeft.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); el.removeAttribute( 'disabled' ); } );
 				if( fragments.next ) dom.controlsRight.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); el.removeAttribute( 'disabled' ); } );
 			}
 
 		}
 
 		if( config.controlsTutorial ) {
 
 			// Highlight control arrows with an animation to ensure
 			// that the viewer knows how to navigate
 			if( !hasNavigatedDown && routes.down ) {
 				dom.controlsDownArrow.classList.add( 'highlight' );
 			}
 			else {
 				dom.controlsDownArrow.classList.remove( 'highlight' );
 
 				if( !hasNavigatedRight && routes.right && indexv === 0 ) {
 					dom.controlsRightArrow.classList.add( 'highlight' );
 				}
 				else {
 					dom.controlsRightArrow.classList.remove( 'highlight' );
 				}
 			}
 
 		}
 
 	}
 
 	/**
 	 * 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 content inside of previous backgrounds
 		if( previousBackground ) {
 
 			stopEmbeddedContent( previousBackground );
 
 		}
 
 		// Start content in the current background
 		if( currentBackground ) {
 
 			startEmbeddedContent( currentBackground );
 
 			var currentBackgroundContent = currentBackground.querySelector( '.slide-background-content' );
 			if( currentBackgroundContent ) {
 
 				var backgroundImageURL = currentBackgroundContent.style.backgroundImage || '';
 
 				// Restart GIFs (doesn't work in Firefox)
 				if( /\.gif/i.test( backgroundImageURL ) ) {
 					currentBackgroundContent.style.backgroundImage = '';
 					window.getComputedStyle( currentBackgroundContent ).opacity;
 					currentBackgroundContent.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 = horizontalSlideCount > 1 ? ( backgroundWidth - slideWidth ) / ( horizontalSlideCount-1 ) : 0;
 			}
 
 			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 : 0;
 
 			dom.background.style.backgroundPosition = horizontalOffset + 'px ' + -verticalOffset + 'px';
 
 		}
 
 	}
 
 	/**
 	 * Should the given element be preloaded?
 	 * Decides based on local element attributes and global config.
 	 *
 	 * @param {HTMLElement} element
 	 */
 	function shouldPreload( element ) {
 
 		// Prefer an explicit global preload setting
 		var preload = config.preloadIframes;
 
 		// If no global setting is available, fall back on the element's
 		// own preload setting
 		if( typeof preload !== 'boolean' ) {
 			preload = element.hasAttribute( 'data-preload' );
 		}
 
 		return preload;
 	}
 
 	/**
 	 * 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).
 	 *
 	 * @param {HTMLElement} slide Slide to show
 	 */
 	function loadSlide( slide, options ) {
 
 		options = options || {};
 
 		// Show the slide element
 		slide.style.display = config.display;
 
 		// Media elements with data-src attributes
 		toArray( slide.querySelectorAll( 'img[data-src], video[data-src], audio[data-src], iframe[data-src]' ) ).forEach( function( element ) {
 			if( element.tagName !== 'IFRAME' || shouldPreload( element ) ) {
 				element.setAttribute( 'src', element.getAttribute( 'data-src' ) );
 				element.setAttribute( 'data-lazy-loaded', '' );
 				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' );
 				source.setAttribute( 'data-lazy-loaded', '' );
 				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 background = slide.slideBackgroundElement;
 		if( background ) {
 			background.style.display = 'block';
 
 			var backgroundContent = slide.slideBackgroundContentElement;
 
 			// 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' ),
 					backgroundVideoMuted = slide.hasAttribute( 'data-background-video-muted' ),
 					backgroundIframe = slide.getAttribute( 'data-background-iframe' );
 
 				// Images
 				if( backgroundImage ) {
 					backgroundContent.style.backgroundImage = 'url('+ encodeURI( backgroundImage ) +')';
 				}
 				// Videos
 				else if ( backgroundVideo && !isSpeakerNotes() ) {
 					var video = document.createElement( 'video' );
 
 					if( backgroundVideoLoop ) {
 						video.setAttribute( 'loop', '' );
 					}
 
 					if( backgroundVideoMuted ) {
 						video.muted = true;
 					}
 
 					// Inline video playback works (at least in Mobile Safari) as
 					// long as the video is muted and the `playsinline` attribute is
 					// present
 					if( isMobileDevice ) {
 						video.muted = true;
 						video.autoplay = true;
 						video.setAttribute( 'playsinline', '' );
 					}
 
 					// Support comma separated lists of video sources
 					backgroundVideo.split( ',' ).forEach( function( source ) {
 						video.innerHTML += '<source src="'+ source +'">';
 					} );
 
 					backgroundContent.appendChild( video );
 				}
 				// Iframes
 				else if( backgroundIframe && options.excludeIframes !== true ) {
 					var iframe = document.createElement( 'iframe' );
 					iframe.setAttribute( 'allowfullscreen', '' );
 					iframe.setAttribute( 'mozallowfullscreen', '' );
 					iframe.setAttribute( 'webkitallowfullscreen', '' );
 
 					// Only load autoplaying content when the slide is shown to
 					// avoid having it play in the background
 					if( /autoplay=(1|true|yes)/gi.test( backgroundIframe ) ) {
 						iframe.setAttribute( 'data-src', backgroundIframe );
 					}
 					else {
 						iframe.setAttribute( 'src', backgroundIframe );
 					}
 
 					iframe.style.width  = '100%';
 					iframe.style.height = '100%';
 					iframe.style.maxHeight = '100%';
 					iframe.style.maxWidth = '100%';
 
 					backgroundContent.appendChild( iframe );
 				}
 			}
 
 		}
 
 	}
 
 	/**
 	 * Unloads and hides the given slide. This is called when the
 	 * slide is moved outside of the configured view distance.
 	 *
 	 * @param {HTMLElement} slide
 	 */
 	function unloadSlide( slide ) {
 
 		// Hide the slide element
 		slide.style.display = 'none';
 
 		// Hide the corresponding background element
 		var background = getSlideBackground( slide );
 		if( background ) {
 			background.style.display = 'none';
 		}
 
 		// Reset lazy-loaded media elements with src attributes
 		toArray( slide.querySelectorAll( 'video[data-lazy-loaded][src], audio[data-lazy-loaded][src], iframe[data-lazy-loaded][src]' ) ).forEach( function( element ) {
 			element.setAttribute( 'data-src', element.getAttribute( 'src' ) );
 			element.removeAttribute( 'src' );
 		} );
 
 		// Reset lazy-loaded media elements with <source> children
 		toArray( slide.querySelectorAll( 'video[data-lazy-loaded] source[src], audio source[src]' ) ).forEach( function( source ) {
 			source.setAttribute( 'data-src', source.getAttribute( 'src' ) );
 			source.removeAttribute( 'src' );
 		} );
 
 	}
 
 	/**
 	 * Determine what available routes there are for navigation.
 	 *
 	 * @return {{left: boolean, right: boolean, up: boolean, down: boolean}}
 	 */
 	function availableRoutes() {
 
 		var horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
 			verticalSlides = dom.wrapper.querySelectorAll( VERTICAL_SLIDES_SELECTOR );
 
 		var routes = {
 			left: indexh > 0,
 			right: indexh < horizontalSlides.length - 1,
 			up: indexv > 0,
 			down: indexv < verticalSlides.length - 1
 		};
 
 		// Looped presentations can always be navigated as long as
 		// there are slides available
 		if( config.loop ) {
 			if( horizontalSlides.length > 1 ) {
 				routes.left = true;
 				routes.right = true;
 			}
 
 			if( verticalSlides.length > 1 ) {
 				routes.up = true;
 				routes.down = true;
 			}
 		}
 
 		// 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 {{prev: boolean, next: boolean}}
 	 */
 	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 given element.
 	 *
 	 * @param {HTMLElement} element
 	 */
 	function startEmbeddedContent( element ) {
 
 		if( element && !isSpeakerNotes() ) {
 
 			// Restart GIFs
 			toArray( element.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( element.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
 				if( closestParent( el, '.fragment' ) && !closestParent( el, '.fragment.visible' ) ) {
 					return;
 				}
 
 				// Prefer an explicit global autoplay setting
 				var autoplay = config.autoPlayMedia;
 
 				// If no global setting is available, fall back on the element's
 				// own autoplay setting
 				if( typeof autoplay !== 'boolean' ) {
 					autoplay = el.hasAttribute( 'data-autoplay' ) || !!closestParent( el, '.slide-background' );
 				}
 
 				if( autoplay && typeof el.play === 'function' ) {
 
 					// If the media is ready, start playback
 					if( el.readyState > 1 ) {
 						startEmbeddedMedia( { target: el } );
 					}
 					// Mobile devices never fire a loaded event so instead
 					// of waiting, we initiate playback
 					else if( isMobileDevice ) {
 						var promise = el.play();
 
 						// If autoplay does not work, ensure that the controls are visible so
 						// that the viewer can start the media on their own
 						if( promise && typeof promise.catch === 'function' && el.controls === false ) {
 							promise.catch( function() {
 								el.controls = true;
 
 								// Once the video does start playing, hide the controls again
 								el.addEventListener( 'play', function() {
 									el.controls = false;
 								} );
 							} );
 						}
 					}
 					// If the media isn't loaded, wait before playing
 					else {
 						el.removeEventListener( 'loadeddata', startEmbeddedMedia ); // remove first to avoid dupes
 						el.addEventListener( 'loadeddata', startEmbeddedMedia );
 					}
 
 				}
 			} );
 
 			// Normal iframes
 			toArray( element.querySelectorAll( 'iframe[src]' ) ).forEach( function( el ) {
 				if( closestParent( el, '.fragment' ) && !closestParent( el, '.fragment.visible' ) ) {
 					return;
 				}
 
 				startEmbeddedIframe( { target: el } );
 			} );
 
 			// Lazy loading iframes
 			toArray( element.querySelectorAll( 'iframe[data-src]' ) ).forEach( function( el ) {
 				if( closestParent( el, '.fragment' ) && !closestParent( el, '.fragment.visible' ) ) {
 					return;
 				}
 
 				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 playing an embedded video/audio element after
 	 * it has finished loading.
 	 *
 	 * @param {object} event
 	 */
 	function startEmbeddedMedia( event ) {
 
 		var isAttachedToDOM = !!closestParent( event.target, 'html' ),
 			isVisible  		= !!closestParent( event.target, '.present' );
 
 		if( isAttachedToDOM && isVisible ) {
 			event.target.currentTime = 0;
 			event.target.play();
 		}
 
 		event.target.removeEventListener( 'loadeddata', startEmbeddedMedia );
 
 	}
 
 	/**
 	 * "Starts" the content of an embedded iframe using the
 	 * postMessage API.
 	 *
 	 * @param {object} event
 	 */
 	function startEmbeddedIframe( event ) {
 
 		var iframe = event.target;
 
 		if( iframe && iframe.contentWindow ) {
 
 			var isAttachedToDOM = !!closestParent( event.target, 'html' ),
 				isVisible  		= !!closestParent( event.target, '.present' );
 
 			if( isAttachedToDOM && isVisible ) {
 
 				// Prefer an explicit global autoplay setting
 				var autoplay = config.autoPlayMedia;
 
 				// If no global setting is available, fall back on the element's
 				// own autoplay setting
 				if( typeof autoplay !== 'boolean' ) {
 					autoplay = iframe.hasAttribute( 'data-autoplay' ) || !!closestParent( iframe, '.slide-background' );
 				}
 
 				// YouTube postMessage API
 				if( /youtube\.com\/embed\//.test( iframe.getAttribute( 'src' ) ) && autoplay ) {
 					iframe.contentWindow.postMessage( '{"event":"command","func":"playVideo","args":""}', '*' );
 				}
 				// Vimeo postMessage API
 				else if( /player\.vimeo\.com\//.test( iframe.getAttribute( 'src' ) ) && 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.
 	 *
 	 * @param {HTMLElement} element
 	 */
 	function stopEmbeddedContent( element, options ) {
 
 		options = extend( {
 			// Defaults
 			unloadIframes: true
 		}, options || {} );
 
 		if( element && element.parentNode ) {
 			// HTML5 media elements
 			toArray( element.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
 				if( !el.hasAttribute( 'data-ignore' ) && typeof el.pause === 'function' ) {
 					el.setAttribute('data-paused-by-reveal', '');
 					el.pause();
 				}
 			} );
 
 			// Generic postMessage API for non-lazy loaded iframes
 			toArray( element.querySelectorAll( 'iframe' ) ).forEach( function( el ) {
 				if( el.contentWindow ) el.contentWindow.postMessage( 'slide:stop', '*' );
 				el.removeEventListener( 'load', startEmbeddedIframe );
 			});
 
 			// YouTube postMessage API
 			toArray( element.querySelectorAll( 'iframe[src*="youtube.com/embed/"]' ) ).forEach( function( el ) {
 				if( !el.hasAttribute( 'data-ignore' ) && el.contentWindow && typeof el.contentWindow.postMessage === 'function' ) {
 					el.contentWindow.postMessage( '{"event":"command","func":"pauseVideo","args":""}', '*' );
 				}
 			});
 
 			// Vimeo postMessage API
 			toArray( element.querySelectorAll( 'iframe[src*="player.vimeo.com/"]' ) ).forEach( function( el ) {
 				if( !el.hasAttribute( 'data-ignore' ) && el.contentWindow && typeof el.contentWindow.postMessage === 'function' ) {
 					el.contentWindow.postMessage( '{"method":"pause"}', '*' );
 				}
 			});
 
 			if( options.unloadIframes === true ) {
 				// Unload lazy-loaded iframes
 				toArray( element.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.
 	 *
 	 * @return {number} Past slide count
 	 */
 	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.
 	 *
 	 * @return {number}
 	 */
 	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 Math.min( pastCount / ( totalCount - 1 ), 1 );
 
 	}
 
 	/**
 	 * Checks if this presentation is running inside of the
 	 * speaker notes window.
 	 *
 	 * @return {boolean}
 	 */
 	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 not fully numeric and there is a name we
 		// can assume that this is a named link
 		if( !/^[0-9]*$/.test( bits[0] ) && name.length ) {
 			var element;
 
 			// Ensure the named link is a valid HTML ID attribute
 			try {
 				element = document.getElementById( decodeURIComponent( name ) );
 			}
 			catch ( error ) { }
 
 			// Ensure that we're not already on a slide with the same name
 			var isSameNameAsCurrentSlide = currentSlide ? currentSlide.getAttribute( 'id' ) === name : false;
 
 			if( element ) {
 				// If the slide exists and is not the current slide...
 				if ( !isSameNameAsCurrentSlide ) {
 					// ...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 {
 			var hashIndexBase = config.hashOneBasedIndex ? 1 : 0;
 
 			// Read the index components of the hash
 			var h = ( parseInt( bits[0], 10 ) - hashIndexBase ) || 0,
 				v = ( parseInt( bits[1], 10 ) - hashIndexBase ) || 0,
 				f;
 
 			if( config.fragmentInURL ) {
 				f = parseInt( bits[2], 10 );
 				if( isNaN( f ) ) {
 					f = undefined;
 				}
 			}
 
 			if( h !== indexh || v !== indexv || f !== undefined ) {
 				slide( h, v, f );
 			}
 		}
 
 	}
 
 	/**
 	 * 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 ) {
 
 		// 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 ) {
 			// If we're configured to push to history OR the history
 			// API is not avaialble.
 			if( config.history || !window.history ) {
 				window.location.hash = locationHash();
 			}
 			// If we're configured to reflect the current slide in the
 			// URL without pushing to history.
 			else if( config.hash ) {
 				window.history.replaceState( null, null, '#' + locationHash() );
 			}
 			// If history and hash are both disabled, a hash may still
 			// be added to the URL by clicking on a href with a hash
 			// target. Counter this by always removing the hash.
 			else {
 				window.history.replaceState( null, null, window.location.pathname + window.location.search );
 			}
 		}
 
 	}
 	/**
 	 * Retrieves the h/v location and fragment 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 {{h: number, v: number, f: number}}
 	 */
 	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 all slides in this presentation.
 	 */
 	function getSlides() {
 
 		return toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ':not(.stack)' ));
 
 	}
 
 	/**
 	 * Returns an array of objects where each object represents the
 	 * attributes on its respective slide.
 	 */
 	function getSlidesAttributes() {
 
 		return getSlides().map( function( slide ) {
 
 			var attributes = {};
 			for( var i = 0; i < slide.attributes.length; i++ ) {
 				var attribute = slide.attributes[ i ];
 				attributes[ attribute.name ] = attribute.value;
 			}
 			return attributes;
 
 		} );
 
 	}
 
 	/**
 	 * Retrieves the total number of slides in this presentation.
 	 *
 	 * @return {number}
 	 */
 	function getTotalSlides() {
 
 		return getSlides().length;
 
 	}
 
 	/**
 	 * Returns the slide element matching the specified index.
 	 *
 	 * @return {HTMLElement}
 	 */
 	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.
 	 *
 	 * @param {mixed} x Horizontal background index OR a slide
 	 * HTML element
 	 * @param {number} y Vertical background index
 	 * @return {(HTMLElement[]|*)}
 	 */
 	function getSlideBackground( x, y ) {
 
 		var slide = typeof x === 'number' ? getSlide( x, y ) : x;
 		if( slide ) {
 			return slide.slideBackgroundElement;
 		}
 
 		return undefined;
 
 	}
 
 	/**
 	 * Retrieves the speaker notes from a slide. Notes can be
 	 * defined in two ways:
 	 * 1. As a data-notes attribute on the slide <section>
 	 * 2. As an <aside class="notes"> inside of the slide
 	 *
 	 * @param {HTMLElement} [slide=currentSlide]
 	 * @return {(string|null)}
 	 */
 	function getSlideNotes( slide ) {
 
 		// Default to the current slide
 		slide = slide || currentSlide;
 
 		// Notes can be specified via the data-notes attribute...
 		if( slide.hasAttribute( 'data-notes' ) ) {
 			return slide.getAttribute( 'data-notes' );
 		}
 
 		// ... or using an <aside class="notes"> element
 		var notesElement = slide.querySelector( 'aside.notes' );
 		if( notesElement ) {
 			return notesElement.innerHTML;
 		}
 
 		return null;
 
 	}
 
 	/**
 	 * Retrieves the current state of the presentation as
 	 * an object. This state can then be restored at any
 	 * time.
 	 *
 	 * @return {{indexh: number, indexv: number, indexf: number, paused: boolean, overview: boolean}}
 	 */
 	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()
 	 * @see {@link getState} generates the parameter `state`
 	 */
 	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.
 	 *
 	 * @param {object[]|*} fragments
 	 * @param {boolean} grouped If true the returned array will contain
 	 * nested arrays for all fragments with the same index
 	 * @return {object[]} sorted Sorted array of fragments
 	 */
 	function sortFragments( fragments, grouped ) {
 
 		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 grouped === true ? ordered : sorted;
 
 	}
 
 	/**
 	 * Refreshes the fragments on the current slide so that they
 	 * have the appropriate classes (.visible + .current-fragment).
 	 *
 	 * @param {number} [index] The index of the current fragment
 	 * @param {array} [fragments] Array containing all fragments
 	 * in the current slide
 	 *
 	 * @return {{shown: array, hidden: array}}
 	 */
 	function updateFragments( index, fragments ) {
 
 		var changedFragments = {
 			shown: [],
 			hidden: []
 		};
 
 		if( currentSlide && config.fragments ) {
 
 			fragments = fragments || sortFragments( currentSlide.querySelectorAll( '.fragment' ) );
 
 			if( fragments.length ) {
 
 				if( typeof index !== 'number' ) {
 					var currentFragment = sortFragments( currentSlide.querySelectorAll( '.fragment.visible' ) ).pop();
 					if( currentFragment ) {
 						index = parseInt( currentFragment.getAttribute( 'data-fragment-index' ) || 0, 10 );
 					}
 				}
 
 				toArray( fragments ).forEach( function( el, i ) {
 
 					if( el.hasAttribute( 'data-fragment-index' ) ) {
 						i = parseInt( el.getAttribute( 'data-fragment-index' ), 10 );
 					}
 
 					// Visible fragments
 					if( i <= index ) {
 						if( !el.classList.contains( 'visible' ) ) changedFragments.shown.push( el );
 						el.classList.add( 'visible' );
 						el.classList.remove( 'current-fragment' );
 
 						// Announce the fragments one by one to the Screen Reader
 						dom.statusDiv.textContent = getStatusText( el );
 
 						if( i === index ) {
 							el.classList.add( 'current-fragment' );
 							startEmbeddedContent( el );
 						}
 					}
 					// Hidden fragments
 					else {
 						if( el.classList.contains( 'visible' ) ) changedFragments.hidden.push( el );
 						el.classList.remove( 'visible' );
 						el.classList.remove( 'current-fragment' );
 					}
 
 				} );
 
 			}
 
 		}
 
 		return changedFragments;
 
 	}
 
 	/**
 	 * 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 changedFragments = updateFragments( index, fragments );
 
 				if( changedFragments.hidden.length ) {
 					dispatchEvent( 'fragmenthidden', { fragment: changedFragments.hidden[0], fragments: changedFragments.hidden } );
 				}
 
 				if( changedFragments.shown.length ) {
 					dispatchEvent( 'fragmentshown', { fragment: changedFragments.shown[0], fragments: changedFragments.shown } );
 				}
 
 				updateControls();
 				updateProgress();
 
 				if( config.fragmentInURL ) {
 					writeURL();
 				}
 
 				return !!( changedFragments.shown.length || changedFragments.hidden.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 && config.autoSlide !== false ) {
 
 			var fragment = currentSlide.querySelector( '.current-fragment' );
 
 			// When the slide first appears there is no "current" fragment so
 			// we look for a data-autoslide timing on the first fragment
 			if( !fragment ) fragment = currentSlide.querySelector( '.fragment' );
 
 			var fragmentAutoSlide = fragment ? fragment.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.
 			// playbackRate is accounted for in the duration.
 			if( currentSlide.querySelectorAll( '.fragment' ).length === 0 ) {
 				toArray( currentSlide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
 					if( el.hasAttribute( 'data-autoplay' ) ) {
 						if( autoSlide && (el.duration * 1000 / el.playbackRate ) > autoSlide ) {
 							autoSlide = ( el.duration * 1000 / el.playbackRate ) + 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( function() {
 					typeof config.autoSlideMethod === 'function' ? config.autoSlideMethod() : navigateNext();
 					cueAutoSlide();
 				}, 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, config.navigationMode === 'grid' ? indexv : undefined );
 			}
 		}
 		// Normal navigation
 		else if( ( isOverview() || previousFragment() === false ) && availableRoutes().left ) {
 			slide( indexh - 1, config.navigationMode === 'grid' ? indexv : undefined );
 		}
 
 	}
 
 	function navigateRight() {
 
 		hasNavigatedRight = true;
 
 		// Reverse for RTL
 		if( config.rtl ) {
 			if( ( isOverview() || previousFragment() === false ) && availableRoutes().right ) {
 				slide( indexh - 1, config.navigationMode === 'grid' ? indexv : undefined );
 			}
 		}
 		// Normal navigation
 		else if( ( isOverview() || nextFragment() === false ) && availableRoutes().right ) {
 			slide( indexh + 1, config.navigationMode === 'grid' ? indexv : undefined );
 		}
 
 	}
 
 	function navigateUp() {
 
 		// Prioritize hiding fragments
 		if( ( isOverview() || previousFragment() === false ) && availableRoutes().up ) {
 			slide( indexh, indexv - 1 );
 		}
 
 	}
 
 	function navigateDown() {
 
 		hasNavigatedDown = true;
 
 		// 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() {
 
 		hasNavigatedRight = true;
 		hasNavigatedDown = true;
 
 		// Prioritize revealing fragments
 		if( nextFragment() === false ) {
 
 			var routes = availableRoutes();
 
 			// When looping is enabled `routes.down` is always available
 			// so we need a separate check for when we've reached the
 			// end of a stack and should move horizontally
 			if( routes.down && routes.right && config.loop && Reveal.isLastVerticalSlide( currentSlide ) ) {
 				routes.down = false;
 			}
 
 			if( routes.down ) {
 				navigateDown();
 			}
 			else if( config.rtl ) {
 				navigateLeft();
 			}
 			else {
 				navigateRight();
 			}
 		}
 
 	}
 
 	/**
 	 * Checks if the target element prevents the triggering of
 	 * swipe navigation.
 	 */
 	function isSwipePrevented( target ) {
 
 		while( target && typeof target.hasAttribute === 'function' ) {
 			if( target.hasAttribute( 'data-prevent-swipe' ) ) return true;
 			target = target.parentNode;
 		}
 
 		return false;
 
 	}
 
 
 	// --------------------------------------------------------------------//
 	// ----------------------------- EVENTS -------------------------------//
 	// --------------------------------------------------------------------//
 
 	/**
 	 * Called by all event handlers that are based on user
 	 * input.
 	 *
 	 * @param {object} [event]
 	 */
 	function onUserInput( event ) {
 
 		if( config.autoSlideStoppable ) {
 			pauseAutoSlide();
 		}
 
 	}
 
 	/**
 	 * Called whenever there is mouse input at the document level
 	 * to determine if the cursor is active or not.
 	 *
 	 * @param {object} event
 	 */
 	function onDocumentCursorActive( event ) {
 
 		showCursor();
 
 		clearTimeout( cursorInactiveTimeout );
 
 		cursorInactiveTimeout = setTimeout( hideCursor, config.hideCursorTime );
 
 	}
 
 	/**
 	 * Handler for the document level 'keypress' event.
 	 *
 	 * @param {object} event
 	 */
 	function onDocumentKeyPress( event ) {
 
 		// Check if the pressed key is question mark
 		if( event.shiftKey && event.charCode === 63 ) {
 			toggleHelp();
 		}
 
 	}
 
 	/**
 	 * Handler for the document level 'keydown' event.
 	 *
 	 * @param {object} event
 	 */
 	function onDocumentKeyDown( event ) {
 
 		// If there's a condition specified and it returns false,
 		// ignore this event
 		if( typeof config.keyboardCondition === 'function' && config.keyboardCondition(event) === false ) {
 			return true;
 		}
 
 		// Shorthand
 		var keyCode = event.keyCode;
 
 		// Remember if auto-sliding was paused so we can toggle it
 		var autoSlideWasPaused = autoSlidePaused;
 
 		onUserInput( event );
 
 		// Is there 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 );
 		var activeElementIsNotes = document.activeElement && document.activeElement.className && /speaker-notes/i.test( document.activeElement.className);
 
 		// Whitelist specific modified + keycode combinations
 		var prevSlideShortcut = event.shiftKey && event.keyCode === 32;
 		var firstSlideShortcut = ( event.metaKey || event.ctrlKey ) && keyCode === 37;
 		var lastSlideShortcut = ( event.metaKey || event.ctrlKey ) && keyCode === 39;
 
 		// Prevent all other events when a modifier is pressed
 		var unusedModifier = 	!prevSlideShortcut && !firstSlideShortcut && !lastSlideShortcut &&
 								( event.shiftKey || event.altKey || event.ctrlKey || event.metaKey );
 
 		// Disregard the event if there's a focused element or a
 		// keyboard modifier key is present
 		if( activeElementIsCE || activeElementIsInput || activeElementIsNotes || unusedModifier ) return;
 
 		// While paused only allow resume keyboard events; 'b', 'v', '.'
 		var resumeKeyCodes = [66,86,190,191];
 		var key;
 
 		// Custom key bindings for togglePause should be able to resume
 		if( typeof config.keyboard === 'object' ) {
 			for( key in config.keyboard ) {
 				if( config.keyboard[key] === 'togglePause' ) {
 					resumeKeyCodes.push( parseInt( key, 10 ) );
 				}
 			}
 		}
 
 		if( isPaused() && resumeKeyCodes.indexOf( keyCode ) === -1 ) {
 			return false;
 		}
 
 		var triggered = false;
 
 		// 1. User defined key bindings
 		if( typeof config.keyboard === 'object' ) {
 
 			for( key in config.keyboard ) {
 
 				// Check if this binding matches the pressed key
 				if( parseInt( key, 10 ) === 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. Registered custom key bindings
 		if( triggered === false ) {
 
 			for( key in registeredKeyBindings ) {
 
 				// Check if this binding matches the pressed key
 				if( parseInt( key, 10 ) === keyCode ) {
 
 					var action = registeredKeyBindings[ key ].callback;
 
 					// Callback function
 					if( typeof action === 'function' ) {
 						action.apply( null, [ event ] );
 					}
 					// String shortcuts to reveal.js API
 					else if( typeof action === 'string' && typeof Reveal[ action ] === 'function' ) {
 						Reveal[ action ].call();
 					}
 
 					triggered = true;
 				}
 			}
 		}
 
 		// 3. System defined key bindings
 		if( triggered === false ) {
 
 			// Assume true and try to prove false
 			triggered = true;
 
 			// P, PAGE UP
 			if( keyCode === 80 || keyCode === 33 ) {
 				navigatePrev();
 			}
 			// N, PAGE DOWN
 			else if( keyCode === 78 || keyCode === 34 ) {
 				navigateNext();
 			}
 			// H, LEFT
 			else if( keyCode === 72 || keyCode === 37 ) {
 				if( firstSlideShortcut ) {
 					slide( 0 );
 				}
 				else if( !isOverview() && config.navigationMode === 'linear' ) {
 					navigatePrev();
 				}
 				else {
 					navigateLeft();
 				}
 			}
 			// L, RIGHT
 			else if( keyCode === 76 || keyCode === 39 ) {
 				if( lastSlideShortcut ) {
 					slide( Number.MAX_VALUE );
 				}
 				else if( !isOverview() && config.navigationMode === 'linear' ) {
 					navigateNext();
 				}
 				else {
 					navigateRight();
 				}
 			}
 			// K, UP
 			else if( keyCode === 75 || keyCode === 38 ) {
 				if( !isOverview() && config.navigationMode === 'linear' ) {
 					navigatePrev();
 				}
 				else {
 					navigateUp();
 				}
 			}
 			// J, DOWN
 			else if( keyCode === 74 || keyCode === 40 ) {
 				if( !isOverview() && config.navigationMode === 'linear' ) {
 					navigateNext();
 				}
 				else {
 					navigateDown();
 				}
 			}
 			// HOME
 			else if( keyCode === 36 ) {
 				slide( 0 );
 			}
 			// END
 			else if( keyCode === 35 ) {
 				slide( Number.MAX_VALUE );
 			}
 			// SPACE
 			else if( keyCode === 32 ) {
 				if( isOverview() ) {
 					deactivateOverview();
 				}
 				if( event.shiftKey ) {
 					navigatePrev();
 				}
 				else {
 					navigateNext();
 				}
 			}
 			// TWO-SPOT, SEMICOLON, B, V, PERIOD, LOGITECH PRESENTER TOOLS "BLACK SCREEN" BUTTON
 			else if( keyCode === 58 || keyCode === 59 || keyCode === 66 || keyCode === 86 || keyCode === 190 || keyCode === 191 ) {
 				togglePause();
 			}
 			// F
 			else if( keyCode === 70 ) {
 				enterFullscreen();
 			}
 			// A
 			else if( keyCode === 65 ) {
 				if ( config.autoSlideStoppable ) {
 					toggleAutoSlide( autoSlideWasPaused );
 				}
 			}
 			else {
 				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 ( ( keyCode === 27 || 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.
 	 *
 	 * @param {object} event
 	 */
 	function onTouchStart( event ) {
 
 		if( isSwipePrevented( event.target ) ) return true;
 
 		touch.startX = event.touches[0].clientX;
 		touch.startY = event.touches[0].clientY;
 		touch.startCount = event.touches.length;
 
 	}
 
 	/**
 	 * Handler for the 'touchmove' event.
 	 *
 	 * @param {object} event
 	 */
 	function onTouchMove( event ) {
 
 		if( isSwipePrevented( event.target ) ) return true;
 
 		// Each touch should only trigger one action
 		if( !touch.captured ) {
 			onUserInput( event );
 
 			var currentX = event.touches[0].clientX;
 			var currentY = event.touches[0].clientY;
 
 			// There was only one touch point, look for a swipe
 			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( UA.match( /android/gi ) ) {
 			event.preventDefault();
 		}
 
 	}
 
 	/**
 	 * Handler for the 'touchend' event.
 	 *
 	 * @param {object} event
 	 */
 	function onTouchEnd( event ) {
 
 		touch.captured = false;
 
 	}
 
 	/**
 	 * Convert pointer down to touch start.
 	 *
 	 * @param {object} event
 	 */
 	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.
 	 *
 	 * @param {object} event
 	 */
 	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.
 	 *
 	 * @param {object} event
 	 */
 	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.
 	 *
 	 * @param {object} event
 	 */
 	function onDocumentMouseScroll( event ) {
 
 		if( Date.now() - lastMouseWheelStep > 600 ) {
 
 			lastMouseWheelStep = Date.now();
 
 			var delta = event.detail || -event.wheelDelta;
 			if( delta > 0 ) {
 				navigateNext();
 			}
 			else if( delta < 0 ) {
 				navigatePrev();
 			}
 
 		}
 
 	}
 
 	/**
 	 * Clicking on the progress bar results in a navigation to the
 	 * closest approximate horizontal slide using this equation:
 	 *
 	 * ( clickX / presentationWidth ) * numberOfSlides
 	 *
 	 * @param {object} event
 	 */
 	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(); config.navigationMode === 'linear' ? navigatePrev() : navigateLeft(); }
 	function onNavigateRightClicked( event ) { event.preventDefault(); onUserInput(); config.navigationMode === 'linear' ? navigateNext() : 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.
 	 *
 	 * @param {object} [event]
 	 */
 	function onWindowHashChange( event ) {
 
 		readURL();
 
 	}
 
 	/**
 	 * Handler for the window level 'resize' event.
 	 *
 	 * @param {object} [event]
 	 */
 	function onWindowResize( event ) {
 
 		layout();
 
 	}
 
 	/**
 	 * Handle for the window level 'visibilitychange' event.
 	 *
 	 * @param {object} [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.
 	 *
 	 * @param {object} event
 	 */
 	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.
 	 *
 	 * @param {object} event
 	 */
 	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.
 	 *
 	 * @param {object} [event]
 	 */
 	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 = 100;
 		this.diameter2 = this.diameter/2;
 		this.thickness = 6;
 
 		// 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.canvas.style.width = this.diameter2 + 'px';
 		this.canvas.style.height = this.diameter2 + 'px';
 		this.context = this.canvas.getContext( '2d' );
 
 		this.container.appendChild( this.canvas );
 
 		this.render();
 
 	}
 
 	/**
 	 * @param value
 	 */
 	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.diameter2 ) - this.thickness,
 			x = this.diameter2,
 			y = this.diameter2,
 			iconSize = 28;
 
 		// 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 + 4, 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 = 'rgba( 255, 255, 255, 0.2 )';
 		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 - 4, iconSize );
 			this.context.fillRect( iconSize / 2 + 4, 0, iconSize / 2 - 4, iconSize );
 		}
 		else {
 			this.context.beginPath();
 			this.context.translate( 4, 0 );
 			this.context.moveTo( 0, 0 );
 			this.context.lineTo( iconSize - 4, 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 = {
 		VERSION: VERSION,
 
 		initialize: initialize,
 		configure: configure,
 
 		sync: sync,
 		syncSlide: syncSlide,
 		syncFragments: syncFragments,
 
 		// 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,
 
 		// Randomizes the order of slides
 		shuffle: shuffle,
 
 		// 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 a help overlay with keyboard shortcuts
 		toggleHelp: toggleHelp,
 
 		// 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,
 		isSpeakerNotes: isSpeakerNotes,
 
 		// Slide preloading
 		loadSlide: loadSlide,
 		unloadSlide: unloadSlide,
 
 		// 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
 		getSlidePastCount: getSlidePastCount,
 
 		// Presentation progress on range of 0-1
 		getProgress: getProgress,
 
 		// Returns the indices of the current, or specified, slide
 		getIndices: getIndices,
 
 		// Returns an Array of all slides
 		getSlides: getSlides,
 
 		// Returns an Array of objects representing the attributes on
 		// the slides
 		getSlidesAttributes: getSlidesAttributes,
 
 		// Returns the total number of slides
 		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 speaker notes string for a slide, or null
 		getSlideNotes: getSlideNotes,
 
 		// 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 the top-level DOM element
 		getRevealElement: function() {
 			return dom.wrapper || document.querySelector( '.reveal' );
 		},
 
 		// Returns a hash with all registered plugins
 		getPlugins: function() {
 			return plugins;
 		},
 
 		// 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 have a next 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;
 		},
 
 		// Returns true if we're on the last slide in the current
 		// vertical stack
 		isLastVerticalSlide: function() {
 			if( currentSlide && isVerticalSlide( currentSlide ) ) {
 				// Does this slide have a next sibling?
 				if( currentSlide.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 ) {
 				Reveal.getRevealElement().addEventListener( type, listener, useCapture );
 			}
 		},
 		removeEventListener: function( type, listener, useCapture ) {
 			if( 'addEventListener' in window ) {
 				Reveal.getRevealElement().removeEventListener( type, listener, useCapture );
 			}
 		},
 
 		// Adds/removes a custom key binding
 		addKeyBinding: addKeyBinding,
 		removeKeyBinding: removeKeyBinding,
 
 		// API for registering and retrieving plugins
 		registerPlugin: registerPlugin,
 		hasPlugin: hasPlugin,
 		getPlugin: getPlugin,
 
 		// Programmatically triggers a keyboard event
 		triggerKey: function( keyCode ) {
 			onDocumentKeyDown( { keyCode: keyCode } );
 		},
 
 		// Registers a new shortcut to include in the help overlay
 		registerKeyboardShortcut: function( key, value ) {
 			keyboardShortcuts[key] = value;
 		}
 	};
 
 	return Reveal;
 
 }));