text: /*!
   * reveal.js
   * http://revealjs.com
   * MIT licensed
   *
   * Copyright (C) 2017 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 = '3.6.0';
  
  	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: false,
  
  			// Display the page number of the current slide
  			slideNumber: false,
  
  			// Determine which displays to show the slide number on
  			showSlideNumber: 'all',
  
  			// Push each slide change to the browser history
  			history: false,
  
  			// Enable keyboard shortcuts for navigation
  			keyboard: true,
  
  			// Optional function that blocks keyboard events when retuning false
  			keyboardCondition: null,
  
  			// Enable the slide overview mode
  			overview: true,
  
  			// Vertical centering of slides
  			center: true,
  
  			// Enables touch navigation on devices with touch input
  			touch: true,
  
  			// Loop the presentation
  			loop: false,
  
  			// Change the presentation direction to be RTL
  			rtl: false,
  
  			// Randomizes the order of slides each time the presentation loads
  			shuffle: false,
  
  			// Turns fragments on and off globally
  			fragments: true,
  
  			// Flags if the presentation is running in an embedded mode,
  			// i.e. contained within a limited portion of the screen
  			embedded: false,
  
  			// Flags if we should show a help overlay when the 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,
  
  			// 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,
  
  			// Enable slide navigation via mouse wheel
  			mouseWheel: false,
  
  			// Apply a 3D roll to links on hover
  			rollingLinks: false,
  
  			// Hides the address bar on mobile devices
  			hideAddressBar: true,
  
  			// Opens links in an iframe preview overlay
  			previewLinks: false,
  
  			// Exposes the reveal.js API through window.postMessage
  			postMessage: true,
  
  			// Dispatches all reveal.js events to the parent window through postMessage
  			postMessageEvents: false,
  
  			// Focuses body when page changes 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"
  
  			// 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,
  
  			// 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',
  
  			// 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 = {},
  
  		// 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,
  
  		// Flags if the interaction event listeners are bound
  		eventsAreBound = false,
  
  		// The current auto-slide duration
  		autoSlide = 0,
  
  		// Auto slide properties
  		autoSlidePlayer,
  		autoSlideTimeout = 0,
  		autoSlideStartTime = -1,
  		autoSlidePaused = false,
  
  		// Holds information about the currently ongoing touch input
  		touch = {
  			startX: 0,
  			startY: 0,
  			startSpan: 0,
  			startCount: 0,
  			captured: false,
  			threshold: 40
  		},
  
  		// Holds information about the keyboard shortcuts
  		keyboardShortcuts = {
  			'N  ,  SPACE':			'Next slide',
  			'P':					'Previous slide',
  			'&#8592;  ,  H':		'Navigate left',
  			'&#8594;  ,  L':		'Navigate right',
  			'&#8593;  ,  K':		'Navigate up',
  			'&#8595;  ,  J':		'Navigate down',
  			'Home':					'First slide',
  			'End':					'Last slide',
  			'B  ,  .':				'Pause',
  			'F':					'Fullscreen',
  			'ESC, O':				'Slide overview'
  		};
  
  	/**
  	 * Starts up the presentation if the client is capable.
  	 */
  	function initialize( options ) {
  
  		// 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 the dependencies and continues to #start() once done
  		load();
  
  	}
  
  	/**
  	 * Inspect the client to see what it's capable of, this
  	 * should only happens once per runtime.
  	 */
  	function checkCapabilities() {
  
  		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 = [],
  			scriptsAsync = [],
  			scriptsToPreload = 0;
  
  		// Called once synchronous scripts finish loading
  		function proceed() {
  			if( scriptsAsync.length ) {
  				// Load asynchronous scripts
  				head.js.apply( null, scriptsAsync );
  			}
  
  			start();
  		}
  
  		function loadScript( s ) {
  			head.ready( s.src.match( /([\w\d_\-]*)\.?js$|[^\\\/]*$/i )[0], function() {
  				// Extension may contain callback functions
  				if( typeof s.callback === 'function' ) {
  					s.callback.apply( this );
  				}
  
  				if( --scriptsToPreload === 0 ) {
  					proceed();
  				}
  			});
  		}
  
  		for( var i = 0, len = config.dependencies.length; i < len; i++ ) {
  			var s = config.dependencies[i];
  
  			// Load if there's no condition or the condition is truthy
  			if( !s.condition || s.condition() ) {
  				if( s.async ) {
  					scriptsAsync.push( s.src );
  				}
  				else {
  					scripts.push( s.src );
  				}
  
  				loadScript( s );
  			}
  		}
  
  		if( scripts.length ) {
  			scriptsToPreload = scripts.length;
  
  			// Load synchronous scripts
  			head.js.apply( null, scripts );
  		}
  		else {
  			proceed();
  		}
  
  	}
  
  	/**
  	 * Starts up reveal.js by binding input events and navigating
  	 * to the current URL deeplink if there is one.
  	 */
  	function start() {
  
  		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
  		createSingletonNode( dom.wrapper, 'div', 'pause-overlay', 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 );
  				}
  			}
  
  		} );
  
  		// Show all fragments
  		toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' .fragment' ) ).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;
  
  			// 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 ) {
  
  		var data = {
  			background: slide.getAttribute( 'data-background' ),
  			backgroundSize: slide.getAttribute( 'data-background-size' ),
  			backgroundImage: slide.getAttribute( 'data-background-image' ),
  			backgroundVideo: slide.getAttribute( 'data-background-video' ),
  			backgroundIframe: slide.getAttribute( 'data-background-iframe' ),
  			backgroundColor: slide.getAttribute( 'data-background-color' ),
  			backgroundRepeat: slide.getAttribute( 'data-background-repeat' ),
  			backgroundPosition: slide.getAttribute( 'data-background-position' ),
  			backgroundTransition: slide.getAttribute( 'data-background-transition' )
  		};
  
  		var element = document.createElement( 'div' );
  
  		// Carry over custom classes from the slide to the background
  		element.className = 'slide-background ' + slide.className.replace( /present|past|future/, '' );
  
  		if( data.background ) {
  			// Auto-wrap image urls in url(...)
  			if( /^(http|file|\/\/)/gi.test( data.background ) || /\.(svg|png|jpg|jpeg|gif|bmp)([?#]|$)/gi.test( data.background ) ) {
  				slide.setAttribute( 'data-background-image', data.background );
  			}
  			else {
  				element.style.background = data.background;
  			}
  		}
  
  		// Create a hash for this combination of background settings.
  		// This is used to determine when two slide backgrounds are
  		// the same.
  		if( data.background || data.backgroundColor || data.backgroundImage || data.backgroundVideo || data.backgroundIframe ) {
  			element.setAttribute( 'data-background-hash', data.background +
  															data.backgroundSize +
  															data.backgroundImage +
  															data.backgroundVideo +
  															data.backgroundIframe +
  															data.backgroundColor +
  															data.backgroundRepeat +
  															data.backgroundPosition +
  															data.backgroundTransition );
  		}
  
  		// Additional and optional background properties
  		if( data.backgroundSize ) element.style.backgroundSize = data.backgroundSize;
  		if( data.backgroundSize ) element.setAttribute( 'data-background-size', data.backgroundSize );
  		if( data.backgroundColor ) element.style.backgroundColor = data.backgroundColor;
  		if( data.backgroundRepeat ) element.style.backgroundRepeat = data.backgroundRepeat;
  		if( data.backgroundPosition ) element.style.backgroundPosition = data.backgroundPosition;
  		if( data.backgroundTransition ) element.setAttribute( 'data-background-transition', data.backgroundTransition );
  
  		container.appendChild( element );
  
  		// If backgrounds are being recreated, clear old classes
  		slide.classList.remove( 'has-dark-background' );
  		slide.classList.remove( 'has-light-background' );
  
  		slide.slideBackgroundElement = element;
  
  		// If this slide has a background color, add a class that
  		// signals if it is light or dark. If the slide has no background
  		// color, no class will be set
  		var computedBackgroundStyle = window.getComputedStyle( element );
  		if( computedBackgroundStyle && computedBackgroundStyle.backgroundColor ) {
  			var rgb = colorToRgb( computedBackgroundStyle.backgroundColor );
  
  			// 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( computedBackgroundStyle.backgroundColor ) < 128 ) {
  					slide.classList.add( 'has-dark-background' );
  				}
  				else {
  					slide.classList.add( 'has-light-background' );
  				}
  			}
  		}
  
  		return element;
  
  	}
  
  	/**
  	 * Registers a listener to postMessage events, this makes it
  	 * possible to call all reveal.js API methods from another
  	 * window. For example:
  	 *
  	 * revealWindow.postMessage( JSON.stringify({
  	 *   method: 'slide',
  	 *   args: [ 2 ]
  	 * }), '*' );
  	 */
  	function setupPostMessage() {
  
  		if( config.postMessage ) {
  			window.addEventListener( 'message', function ( event ) {
  				var data = event.data;
  
  				// Make sure we're dealing with JSON
  				if( typeof data === 'string' && data.charAt( 0 ) === '{' && data.charAt( data.length - 1 ) === '}' ) {
  					data = JSON.parse( data );
  
  					// Check if the requested method can be found
  					if( data.method && typeof Reveal[data.method] === 'function' ) {
  						Reveal[data.method].apply( Reveal, data.args );
  					}
  				}
  			}, false );
  		}
  
  	}
  
  	/**
  	 * Applies the configuration settings from the config
  	 * object. May be called multiple times.
  	 *
  	 * @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();
  		}
  
  		// 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;
  
  		sync();
  
  	}
  
  	/**
  	 * Binds all event listeners.
  	 */
  	function addEventListeners() {
  
  		eventsAreBound = true;
  
  		window.addEventListener( 'hashchange', onWindowHashChange, false );
  		window.addEventListener( 'resize', onWindowResize, false );
  
  		if( config.touch ) {
  			dom.wrapper.addEventListener( 'touchstart', onTouchStart, false );
  			dom.wrapper.addEventListener( 'touchmove', onTouchMove, false );
  			dom.wrapper.addEventListener( 'touchend', onTouchEnd, false );
  
  			// Support pointer-style touch interaction as well
  			if( window.navigator.pointerEnabled ) {
  				// IE 11 uses un-prefixed version of pointer events
  				dom.wrapper.addEventListener( 'pointerdown', onPointerDown, false );
  				dom.wrapper.addEventListener( 'pointermove', onPointerMove, false );
  				dom.wrapper.addEventListener( 'pointerup', onPointerUp, false );
  			}
  			else if( window.navigator.msPointerEnabled ) {
  				// IE 10 uses prefixed version of pointer events
  				dom.wrapper.addEventListener( 'MSPointerDown', onPointerDown, false );
  				dom.wrapper.addEventListener( 'MSPointerMove', onPointerMove, false );
  				dom.wrapper.addEventListener( 'MSPointerUp', onPointerUp, false );
  			}
  		}
  
  		if( config.keyboard ) {
  			document.addEventListener( 'keydown', onDocumentKeyDown, false );
  			document.addEventListener( 'keypress', onDocumentKeyPress, false );
  		}
  
  		if( config.progress && dom.progress ) {
  			dom.progress.addEventListener( 'click', onProgressClicked, false );
  		}
  
  		if( config.focusBodyOnPageVisibilityChange ) {
  			var visibilityChange;
  
  			if( 'hidden' in document ) {
  				visibilityChange = 'visibilitychange';
  			}
  			else if( 'msHidden' in document ) {
  				visibilityChange = 'msvisibilitychange';
  			}
  			else if( 'webkitHidden' in document ) {
  				visibilityChange = 'webkitvisibilitychange';
  			}
  
  			if( visibilityChange ) {
  				document.addEventListener( visibilityChange, onPageVisibilityChange, false );
  			}
  		}
  
  		// Listen to both touch and click events, in case the device
  		// supports both
  		var pointerEvents = [ 'touchstart', 'click' ];
  
  		// Only support touch for Android, fixes double navigations in
  		// stock browser
  		if( 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( 'touchstart', onTouchStart, false );
  		dom.wrapper.removeEventListener( 'touchmove', onTouchMove, false );
  		dom.wrapper.removeEventListener( 'touchend', onTouchEnd, false );
  
  		// IE11
  		if( window.navigator.pointerEnabled ) {
  			dom.wrapper.removeEventListener( 'pointerdown', onPointerDown, false );
  			dom.wrapper.removeEventListener( 'pointermove', onPointerMove, false );
  			dom.wrapper.removeEventListener( 'pointerup', onPointerUp, false );
  		}
  		// IE10
  		else if( window.navigator.msPointerEnabled ) {
  			dom.wrapper.removeEventListener( 'MSPointerDown', onPointerDown, false );
  			dom.wrapper.removeEventListener( 'MSPointerMove', onPointerMove, false );
  			dom.wrapper.removeEventListener( 'MSPointerUp', onPointerUp, false );
  		}
  
  		if ( config.progress && dom.progress ) {
  			dom.progress.removeEventListener( 'click', onProgressClicked, false );
  		}
  
  		[ 'touchstart', 'click' ].forEach( function( eventName ) {
  			dom.controlsLeft.forEach( function( el ) { el.removeEventListener( eventName, onNavigateLeftClicked, false ); } );
  			dom.controlsRight.forEach( function( el ) { el.removeEventListener( eventName, onNavigateRightClicked, false ); } );
  			dom.controlsUp.forEach( function( el ) { el.removeEventListener( eventName, onNavigateUpClicked, false ); } );
  			dom.controlsDown.forEach( function( el ) { el.removeEventListener( eventName, onNavigateDownClicked, false ); } );
  			dom.controlsPrev.forEach( function( el ) { el.removeEventListener( eventName, onNavigatePrevClicked, false ); } );
  			dom.controlsNext.forEach( function( el ) { el.removeEventListener( eventName, onNavigateNextClicked, false ); } );
  		} );
  
  	}
  
  	/**
  	 * Extend object a with the properties of object b.
  	 * If there's a conflict, object b takes precedence.
  	 *
  	 * @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';
  			newHeight = height - element.parentNode.offsetHeight;
  
  			// Restore the old height, just in case
  			element.style.height = oldHeight + 'px';
  
  			return newHeight;
  		}
  
  		return height;
  
  	}
  
  	/**
  	 * Checks if this instance is being used to print a PDF.
  	 */
  	function isPrintingPDF() {
  
  		return ( /print-pdf/gi ).test( window.location.search );
  
  	}
  
  	/**
  	 * Hides the address bar if we're on a mobile device.
  	 */
  	function hideAddressBar() {
  
  		if( config.hideAddressBar && isMobileDevice ) {
  			// Events that should trigger the address bar to hide
  			window.addEventListener( 'load', removeAddressBar, false );
  			window.addEventListener( 'orientationchange', removeAddressBar, false );
  		}
  
  	}
  
  	/**
  	 * Causes the address bar to hide on mobile devices,
  	 * more vertical space ftw.
  	 */
  	function removeAddressBar() {
  
  		setTimeout( function() {
  			window.scrollTo( 0, 1 );
  		}, 10 );
  
  	}
  
  	/**
  	 * Dispatches an event of the specified type from the
  	 * reveal DOM element.
  	 */
  	function dispatchEvent( type, args ) {
  
  		var event = document.createEvent( 'HTMLEvents', 1, 2 );
  		event.initEvent( type, true, true );
  		extend( event, args );
  		dom.wrapper.dispatchEvent( event );
  
  		// If we're in an iframe, post each reveal.js event to the
  		// parent window. Used by the notes plugin
  		if( config.postMessageEvents && window.parent !== window.self ) {
  			window.parent.postMessage( JSON.stringify({ namespace: 'reveal', eventName: type, state: getState() }), '*' );
  		}
  
  	}
  
  	/**
  	 * Wrap all links in 3D goodness.
  	 */
  	function enableRollingLinks() {
  
  		if( features.transforms3d && !( 'msPerspective' in document.body.style ) ) {
  			var anchors = dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' a' );
  
  			for( var i = 0, len = anchors.length; i < len; i++ ) {
  				var anchor = anchors[i];
  
  				if( anchor.textContent && !anchor.querySelector( '*' ) && ( !anchor.className || !anchor.classList.contains( anchor, 'roll' ) ) ) {
  					var span = document.createElement('span');
  					span.setAttribute('data-title', anchor.text);
  					span.innerHTML = anchor.innerHTML;
  
  					anchor.classList.add( 'roll' );
  					anchor.innerHTML = '';
  					anchor.appendChild(span);
  				}
  			}
  		}
  
  	}
  
  	/**
  	 * Unwrap all 3D links.
  	 */
  	function disableRollingLinks() {
  
  		var anchors = dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' a.roll' );
  
  		for( var i = 0, len = anchors.length; i < len; i++ ) {
  			var anchor = anchors[i];
  			var span = anchor.querySelector( 'span' );
  
  			if( span ) {
  				anchor.classList.remove( 'roll' );
  				anchor.innerHTML = span.innerHTML;
  			}
  		}
  
  	}
  
  	/**
  	 * Bind preview frame links.
  	 *
  	 * @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>';
  			}
  
  			html += '</table>';
  
  			dom.overlay.innerHTML = [
  				'<header>',
  					'<a class="close" href="#"><span class="icon"></span></a>',
  				'</header>',
  				'<div class="viewport">',
  					'<div class="viewport-inner">'+ html +'</div>',
  				'</div>'
  			].join('');
  
  			dom.overlay.querySelector( '.close' ).addEventListener( 'click', function( event ) {
  				closeOverlay();
  				event.preventDefault();
  			}, false );
  
  			setTimeout( function() {
  				dom.overlay.classList.add( 'visible' );
  			}, 1 );
  
  		}
  
  	}
  
  	/**
  	 * Closes any currently open overlay.
  	 */
  	function closeOverlay() {
  
  		if( dom.overlay ) {
  			dom.overlay.parentNode.removeChild( dom.overlay );
  			dom.overlay = null;
  		}
  
  	}
  
  	/**
  	 * Applies JavaScript-controlled layout rules to the
  	 * presentation.
  	 */
  	function layout() {
  
  		if( dom.wrapper && !isPrintingPDF() ) {
  
  			var size = getComputedSlideSize();
  
  			// 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 = '';
  				}
  
  			}
  
  			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;
  
  	}
  
  	/**
  	 * 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 );
  		}
  
  	}
  
  	/**
  	 * 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();
  
  		// Apply the new state
  		stateLoop: for( var i = 0, len = state.length; i < len; i++ ) {
  			// Check if this state existed on the previous slide. If it
  			// did, we will avoid adding it repeatedly
  			for( var j = 0; j < stateBefore.length; j++ ) {
  				if( stateBefore[j] === state[i] ) {
  					stateBefore.splice( j, 1 );
  					continue stateLoop;
  				}
  			}
  
  			document.documentElement.classList.add( state[i] );
  
  			// Dispatch custom event matching the state's name
  			dispatchEvent( state[i] );
  		}
  
  		// Clean up the remains of the previous state
  		while( stateBefore.length ) {
  			document.documentElement.classList.remove( stateBefore.pop() );
  		}
  
  		// Update the overview if it's currently active
  		if( isOverview() ) {
  			updateOverview();
  		}
  
  		// Find the current horizontal slide and any possible vertical slides
  		// within it
  		var currentHorizontalSlide = horizontalSlides[ indexh ],
  			currentVerticalSlides = currentHorizontalSlide.querySelectorAll( 'section' );
  
  		// Store references to the previous and current slides
  		currentSlide = currentVerticalSlides[ indexv ] || currentHorizontalSlide;
  
  		// Show fragment, if specified
  		if( typeof f !== 'undefined' ) {
  			navigateFragment( f );
  		}
  
  		// Dispatch an event if the slide changed
  		var slideChanged = ( indexh !== indexhBefore || indexv !== indexvBefore );
  		if( slideChanged ) {
  			dispatchEvent( 'slidechanged', {
  				'indexh': indexh,
  				'indexv': indexv,
  				'previousSlide': previousSlide,
  				'currentSlide': currentSlide,
  				'origin': o
  			} );
  		}
  		else {
  			// Ensure that the previous slide is never the same as the current
  			previousSlide = null;
  		}
  
  		// Solves an edge case where the previous slide maintains the
  		// 'present' class when navigating between adjacent vertical
  		// stacks
  		if( previousSlide ) {
  			previousSlide.classList.remove( 'present' );
  			previousSlide.setAttribute( 'aria-hidden', 'true' );
  
  			// Reset all slides upon navigate to home
  			// Issue: #285
  			if ( dom.wrapper.querySelector( HOME_SLIDE_SELECTOR ).classList.contains( 'present' ) ) {
  				// Launch async task
  				setTimeout( function () {
  					var slides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.stack') ), i;
  					for( i in slides ) {
  						if( slides[i] ) {
  							// Reset stack
  							setPreviousVerticalIndex( slides[i], 0 );
  						}
  					}
  				}, 0 );
  			}
  		}
  
  		// Handle embedded content
  		if( slideChanged || !previousSlide ) {
  			stopEmbeddedContent( previousSlide );
  			startEmbeddedContent( currentSlide );
  		}
  
  		// Announce the current slide contents, for screen readers
  		dom.statusDiv.textContent = getStatusText( currentSlide );
  
  		updateControls();
  		updateProgress();
  		updateBackground();
  		updateParallax();
  		updateSlideNumber();
  		updateNotes();
  
  		// 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();
  		}
  
  	}
  
  	/**
  	 * 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 ) {
  						var pastFragments = toArray( element.querySelectorAll( '.fragment' ) );
  
  						// Show all fragments on prior slides
  						while( pastFragments.length ) {
  							var pastFragment = pastFragments.pop();
  							pastFragment.classList.add( 'visible' );
  							pastFragment.classList.remove( 'current-fragment' );
  						}
  					}
  				}
  				else if( i > index ) {
  					// Any element subsequent to index is given the 'future' class
  					element.classList.add( reverse ? 'past' : 'future' );
  
  					if( config.fragments ) {
  						var futureFragments = toArray( element.querySelectorAll( '.fragment.visible' ) );
  
  						// No fragments in future slides should be visible ahead of time
  						while( futureFragments.length ) {
  							var futureFragment = futureFragments.pop();
  							futureFragment.classList.remove( 'visible' );
  							futureFragment.classList.remove( 'current-fragment' );
  						}
  					}
  				}
  			}
  
  			// Mark the current slide as present
  			slides[index].classList.add( 'present' );
  			slides[index].removeAttribute( 'hidden' );
  			slides[index].removeAttribute( 'aria-hidden' );
  
  			// If this slide has a state associated with it, add it
  			// onto the current state of the deck
  			var slideState = slides[index].getAttribute( 'data-state' );
  			if( slideState ) {
  				state = state.concat( slideState.split( ' ' ) );
  			}
  
  		}
  		else {
  			// Since there are no slides we can't be anywhere beyond the
  			// zeroth index
  			index = 0;
  		}
  
  		return index;
  
  	}
  
  	/**
  	 * Optimization method; hide all slides that are far away
  	 * from the present slide.
  	 */
  	function updateSlidesVisibility() {
  
  		// Select all slides and convert the NodeList result to
  		// an array
  		var horizontalSlides = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ),
  			horizontalSlidesLength = horizontalSlides.length,
  			distanceX,
  			distanceY;
  
  		if( horizontalSlidesLength && typeof indexh !== 'undefined' ) {
  
  			// The number of steps away from the present slide that will
  			// be visible
  			var viewDistance = isOverview() ? 10 : config.viewDistance;
  
  			// Limit view distance on weaker devices
  			if( isMobileDevice ) {
  				viewDistance = isOverview() ? 6 : 2;
  			}
  
  			// All slides need to be visible when exporting to PDF
  			if( isPrintingPDF() ) {
  				viewDistance = Number.MAX_VALUE;
  			}
  
  			for( var x = 0; x < horizontalSlidesLength; x++ ) {
  				var horizontalSlide = horizontalSlides[x];
  
  				var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) ),
  					verticalSlidesLength = verticalSlides.length;
  
  				// Determine how far away this slide is from the present
  				distanceX = Math.abs( ( indexh || 0 ) - x ) || 0;
  
  				// If the presentation is looped, distance should measure
  				// 1 between the first and last slides
  				if( config.loop ) {
  					distanceX = Math.abs( ( ( indexh || 0 ) - x ) % ( horizontalSlidesLength - viewDistance ) ) || 0;
  				}
  
  				// Show the horizontal slide if it's within the view distance
  				if( distanceX < viewDistance ) {
  					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 div to reflect the current slide.
  	 *
  	 * The following slide number formats are available:
  	 *  "h.v":	horizontal . vertical slide number (default)
  	 *  "h/v":	horizontal / vertical slide number
  	 *    "c":	flattened slide number
  	 *  "c/t":	flattened slide number / total slides
  	 */
  	function updateSlideNumber() {
  
  		// Update slide number if enabled
  		if( config.slideNumber && dom.slideNumber ) {
  
  			var value = [];
  			var format = 'h.v';
  
  			// Check if a custom number format is available
  			if( typeof config.slideNumber === 'string' ) {
  				format = config.slideNumber;
  			}
  
  			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 ) {
  
  		if( typeof b === 'number' && !isNaN( b ) ) {
  			return  '<span class="slide-number-a">'+ a +'</span>' +
  					'<span class="slide-number-delimiter">'+ delimiter +'</span>' +
  					'<span class="slide-number-b">'+ b +'</span>';
  		}
  		else {
  			return '<span class="slide-number-a">'+ a +'</span>';
  		}
  
  	}
  
  	/**
  	 * 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 backgroundImageURL = currentBackground.style.backgroundImage || '';
  
  			// Restart GIFs (doesn't work in Firefox)
  			if( /\.gif/i.test( backgroundImageURL ) ) {
  				currentBackground.style.backgroundImage = '';
  				window.getComputedStyle( currentBackground ).opacity;
  				currentBackground.style.backgroundImage = backgroundImageURL;
  			}
  
  			// Don't transition between identical backgrounds. This
  			// prevents unwanted flicker.
  			var previousBackgroundHash = previousBackground ? previousBackground.getAttribute( 'data-background-hash' ) : null;
  			var currentBackgroundHash = currentBackground.getAttribute( 'data-background-hash' );
  			if( currentBackgroundHash && currentBackgroundHash === previousBackgroundHash && currentBackground !== previousBackground ) {
  				dom.background.classList.add( 'no-transition' );
  			}
  
  			previousBackground = currentBackground;
  
  		}
  
  		// If there's a background brightness flag for this slide,
  		// bubble it to the .reveal container
  		if( currentSlide ) {
  			[ 'has-light-background', 'has-dark-background' ].forEach( function( classToBubble ) {
  				if( currentSlide.classList.contains( classToBubble ) ) {
  					dom.wrapper.classList.add( classToBubble );
  				}
  				else {
  					dom.wrapper.classList.remove( classToBubble );
  				}
  			} );
  		}
  
  		// Allow the first background to apply without transition
  		setTimeout( function() {
  			dom.background.classList.remove( 'no-transition' );
  		}, 1 );
  
  	}
  
  	/**
  	 * Updates the position of the parallax background based
  	 * on the current slide index.
  	 */
  	function updateParallax() {
  
  		if( config.parallaxBackgroundImage ) {
  
  			var horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
  				verticalSlides = dom.wrapper.querySelectorAll( VERTICAL_SLIDES_SELECTOR );
  
  			var backgroundSize = dom.background.style.backgroundSize.split( ' ' ),
  				backgroundWidth, backgroundHeight;
  
  			if( backgroundSize.length === 1 ) {
  				backgroundWidth = backgroundHeight = parseInt( backgroundSize[0], 10 );
  			}
  			else {
  				backgroundWidth = parseInt( backgroundSize[0], 10 );
  				backgroundHeight = parseInt( backgroundSize[1], 10 );
  			}
  
  			var slideWidth = dom.background.offsetWidth,
  				horizontalSlideCount = horizontalSlides.length,
  				horizontalOffsetMultiplier,
  				horizontalOffset;
  
  			if( typeof config.parallaxBackgroundHorizontal === 'number' ) {
  				horizontalOffsetMultiplier = config.parallaxBackgroundHorizontal;
  			}
  			else {
  				horizontalOffsetMultiplier = 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';
  
  		}
  
  	}
  
  	/**
  	 * 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]' ) ).forEach( function( 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 indices = getIndices( slide );
  		var background = getSlideBackground( indices.h, indices.v );
  		if( background ) {
  			background.style.display = 'block';
  
  			// If the background contains media, load it
  			if( background.hasAttribute( 'data-loaded' ) === false ) {
  				background.setAttribute( 'data-loaded', 'true' );
  
  				var backgroundImage = slide.getAttribute( 'data-background-image' ),
  					backgroundVideo = slide.getAttribute( 'data-background-video' ),
  					backgroundVideoLoop = slide.hasAttribute( 'data-background-video-loop' ),
  					backgroundVideoMuted = slide.hasAttribute( 'data-background-video-muted' ),
  					backgroundIframe = slide.getAttribute( 'data-background-iframe' );
  
  				// Images
  				if( backgroundImage ) {
  					background.style.backgroundImage = 'url('+ backgroundImage +')';
  				}
  				// Videos
  				else if ( backgroundVideo && !isSpeakerNotes() ) {
  					var video = document.createElement( 'video' );
  
  					if( backgroundVideoLoop ) {
  						video.setAttribute( 'loop', '' );
  					}
  
  					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 +'">';
  					} );
  
  					background.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%';
  
  					background.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 indices = getIndices( slide );
  		var background = getSlideBackground( indices.h, indices.v );
  		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]' ) ).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 || config.loop,
  			right: indexh < horizontalSlides.length - 1 || config.loop,
  			up: indexv > 0,
  			down: indexv < verticalSlides.length - 1
  		};
  
  		// reverse horizontal controls for rtl
  		if( config.rtl ) {
  			var left = routes.left;
  			routes.left = routes.right;
  			routes.right = left;
  		}
  
  		return routes;
  
  	}
  
  	/**
  	 * Returns an object describing the available fragment
  	 * directions.
  	 *
  	 * @return {{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' );
  
  		// Always show media controls on mobile devices
  		if( isMobileDevice ) {
  			toArray( dom.slides.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
  				el.controls = true;
  			} );
  		}
  
  	}
  
  	/**
  	 * 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( el.readyState > 1 ) {
  						startEmbeddedMedia( { target: el } );
  					}
  					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 pastCount / ( totalCount - 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 invalid and there is a name we can
  		// assume that this is a named link
  		if( isNaN( parseInt( bits[0], 10 ) ) && name.length ) {
  			var element;
  
  			// Ensure the named link is a valid HTML ID attribute
  			if( /^[a-zA-Z][\w:.-]*$/.test( name ) ) {
  				// Find the slide with the specified ID
  				element = document.getElementById( name );
  			}
  
  			if( element ) {
  				// Find the position of the named slide and navigate to it
  				var indices = Reveal.getIndices( element );
  				slide( indices.h, indices.v );
  			}
  			// If the slide doesn't exist, navigate to the current slide
  			else {
  				slide( indexh || 0, indexv || 0 );
  			}
  		}
  		else {
  			// Read the index components of the hash
  			var h = parseInt( bits[0], 10 ) || 0,
  				v = parseInt( bits[1], 10 ) || 0;
  
  			if( h !== indexh || v !== indexv ) {
  				slide( h, v );
  			}
  		}
  
  	}
  
  	/**
  	 * Updates the page URL (hash) to reflect the current
  	 * state.
  	 *
  	 * @param {number} delay The time in ms to wait before
  	 * writing the hash
  	 */
  	function writeURL( delay ) {
  
  		if( config.history ) {
  
  			// Make sure there's never more than one timeout running
  			clearTimeout( writeURLTimeout );
  
  			// If a delay is specified, timeout this call
  			if( typeof delay === 'number' ) {
  				writeURLTimeout = setTimeout( writeURL, delay );
  			}
  			else if( currentSlide ) {
  				var url = '/';
  
  				// Attempt to create a named link based on the slide's ID
  				var id = currentSlide.getAttribute( 'id' );
  				if( id ) {
  					id = id.replace( /[^a-zA-Z0-9\-\_\:\.]/g, '' );
  				}
  
  				// If the current slide has an ID, use that as a named link
  				if( typeof id === 'string' && id.length ) {
  					url = '/' + id;
  				}
  				// Otherwise use the /h/v index
  				else {
  					if( indexh > 0 || indexv > 0 ) url += indexh;
  					if( indexv > 0 ) url += '/' + indexv;
  				}
  
  				window.location.hash = url;
  			}
  		}
  
  	}
  	/**
  	 * Retrieves the h/v location 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)' ));
  
  	}
  
  	/**
  	 * 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 {number} x Horizontal background index
  	 * @param {number} y Vertical background index
  	 * @return {(HTMLElement[]|*)}
  	 */
  	function getSlideBackground( x, y ) {
  
  		var slide = getSlide( x, y );
  		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
  	 * @return {object[]} sorted Sorted array of fragments
  	 */
  	function sortFragments( fragments ) {
  
  		fragments = toArray( fragments );
  
  		var ordered = [],
  			unordered = [],
  			sorted = [];
  
  		// Group ordered and unordered elements
  		fragments.forEach( function( fragment, i ) {
  			if( fragment.hasAttribute( 'data-fragment-index' ) ) {
  				var index = parseInt( fragment.getAttribute( 'data-fragment-index' ), 10 );
  
  				if( !ordered[index] ) {
  					ordered[index] = [];
  				}
  
  				ordered[index].push( fragment );
  			}
  			else {
  				unordered.push( [ fragment ] );
  			}
  		} );
  
  		// Append fragments without explicit indices in their
  		// DOM order
  		ordered = ordered.concat( unordered );
  
  		// Manually count the index up per group to ensure there
  		// are no gaps
  		var index = 0;
  
  		// Push all fragments in their sorted order to an array,
  		// this flattens the groups
  		ordered.forEach( function( group ) {
  			group.forEach( function( fragment ) {
  				sorted.push( fragment );
  				fragment.setAttribute( 'data-fragment-index', index );
  			} );
  
  			index ++;
  		} );
  
  		return sorted;
  
  	}
  
  	/**
  	 * Navigate to the specified slide fragment.
  	 *
  	 * @param {?number} index The index of the fragment that
  	 * should be shown, -1 means all are invisible
  	 * @param {number} offset Integer offset to apply to the
  	 * fragment index
  	 *
  	 * @return {boolean} true if a change was made in any
  	 * fragments visibility as part of this call
  	 */
  	function navigateFragment( index, offset ) {
  
  		if( currentSlide && config.fragments ) {
  
  			var fragments = sortFragments( currentSlide.querySelectorAll( '.fragment' ) );
  			if( fragments.length ) {
  
  				// If no index is specified, find the current
  				if( typeof index !== 'number' ) {
  					var lastVisibleFragment = sortFragments( currentSlide.querySelectorAll( '.fragment.visible' ) ).pop();
  
  					if( lastVisibleFragment ) {
  						index = parseInt( lastVisibleFragment.getAttribute( 'data-fragment-index' ) || 0, 10 );
  					}
  					else {
  						index = -1;
  					}
  				}
  
  				// If an offset is specified, apply it to the index
  				if( typeof offset === 'number' ) {
  					index += offset;
  				}
  
  				var fragmentsShown = [],
  					fragmentsHidden = [];
  
  				toArray( fragments ).forEach( function( element, i ) {
  
  					if( element.hasAttribute( 'data-fragment-index' ) ) {
  						i = parseInt( element.getAttribute( 'data-fragment-index' ), 10 );
  					}
  
  					// Visible fragments
  					if( i <= index ) {
  						if( !element.classList.contains( 'visible' ) ) fragmentsShown.push( element );
  						element.classList.add( 'visible' );
  						element.classList.remove( 'current-fragment' );
  
  						// Announce the fragments one by one to the Screen Reader
  						dom.statusDiv.textContent = getStatusText( element );
  
  						if( i === index ) {
  							element.classList.add( 'current-fragment' );
  							startEmbeddedContent( element );
  						}
  					}
  					// Hidden fragments
  					else {
  						if( element.classList.contains( 'visible' ) ) fragmentsHidden.push( element );
  						element.classList.remove( 'visible' );
  						element.classList.remove( 'current-fragment' );
  					}
  
  				} );
  
  				if( fragmentsHidden.length ) {
  					dispatchEvent( 'fragmenthidden', { fragment: fragmentsHidden[0], fragments: fragmentsHidden } );
  				}
  
  				if( fragmentsShown.length ) {
  					dispatchEvent( 'fragmentshown', { fragment: fragmentsShown[0], fragments: fragmentsShown } );
  				}
  
  				updateControls();
  				updateProgress();
  
  				return !!( fragmentsShown.length || fragmentsHidden.length );
  
  			}
  
  		}
  
  		return false;
  
  	}
  
  	/**
  	 * Navigate to the next slide fragment.
  	 *
  	 * @return {boolean} true if there was a next fragment,
  	 * false otherwise
  	 */
  	function nextFragment() {
  
  		return navigateFragment( null, 1 );
  
  	}
  
  	/**
  	 * Navigate to the previous slide fragment.
  	 *
  	 * @return {boolean} true if there was a previous fragment,
  	 * false otherwise
  	 */
  	function previousFragment() {
  
  		return navigateFragment( null, -1 );
  
  	}
  
  	/**
  	 * Cues a new automated slide if enabled in the config.
  	 */
  	function cueAutoSlide() {
  
  		cancelAutoSlide();
  
  		if( currentSlide && 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 );
  			}
  		}
  		// Normal navigation
  		else if( ( isOverview() || previousFragment() === false ) && availableRoutes().left ) {
  			slide( indexh - 1 );
  		}
  
  	}
  
  	function navigateRight() {
  
  		hasNavigatedRight = true;
  
  		// Reverse for RTL
  		if( config.rtl ) {
  			if( ( isOverview() || previousFragment() === false ) && availableRoutes().right ) {
  				slide( indexh - 1 );
  			}
  		}
  		// Normal navigation
  		else if( ( isOverview() || nextFragment() === false ) && availableRoutes().right ) {
  			slide( indexh + 1 );
  		}
  
  	}
  
  	function navigateUp() {
  
  		// Prioritize hiding fragments
  		if( ( isOverview() || previousFragment() === false ) && availableRoutes().up ) {
  			slide( indexh, indexv - 1 );
  		}
  
  	}
  
  	function navigateDown() {
  
  		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 ) {
  			if( availableRoutes().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();
  		}
  
  	}
  
  	/**
  	 * 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() === false ) {
  			return true;
  		}
  
  		// Remember if auto-sliding was paused so we can toggle it
  		var autoSlideWasPaused = autoSlidePaused;
  
  		onUserInput( event );
  
  		// Check if there's a focused element that could be using
  		// the keyboard
  		var activeElementIsCE = document.activeElement && document.activeElement.contentEditable !== 'inherit';
  		var activeElementIsInput = document.activeElement && document.activeElement.tagName && /input|textarea/i.test( document.activeElement.tagName );
  		var activeElementIsNotes = document.activeElement && document.activeElement.className && /speaker-notes/i.test( document.activeElement.className);
  
  		// Disregard the event if there's a focused element or a
  		// keyboard modifier key is present
  		if( activeElementIsCE || activeElementIsInput || activeElementIsNotes || (event.shiftKey && event.keyCode !== 32) || event.altKey || event.ctrlKey || event.metaKey ) 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( event.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 ) === event.keyCode ) {
  
  					var value = config.keyboard[ key ];
  
  					// Callback function
  					if( typeof value === 'function' ) {
  						value.apply( null, [ event ] );
  					}
  					// String shortcuts to reveal.js API
  					else if( typeof value === 'string' && typeof Reveal[ value ] === 'function' ) {
  						Reveal[ value ].call();
  					}
  
  					triggered = true;
  
  				}
  
  			}
  
  		}
  
  		// 2. System defined key bindings
  		if( triggered === false ) {
  
  			// Assume true and try to prove false
  			triggered = true;
  
  			switch( event.keyCode ) {
  				// p, page up
  				case 80: case 33: navigatePrev(); break;
  				// n, page down
  				case 78: case 34: navigateNext(); break;
  				// h, left
  				case 72: case 37: navigateLeft(); break;
  				// l, right
  				case 76: case 39: navigateRight(); break;
  				// k, up
  				case 75: case 38: navigateUp(); break;
  				// j, down
  				case 74: case 40: navigateDown(); break;
  				// home
  				case 36: slide( 0 ); break;
  				// end
  				case 35: slide( Number.MAX_VALUE ); break;
  				// space
  				case 32: isOverview() ? deactivateOverview() : event.shiftKey ? navigatePrev() : navigateNext(); break;
  				// return
  				case 13: isOverview() ? deactivateOverview() : triggered = false; break;
  				// two-spot, semicolon, b, v, period, Logitech presenter tools "black screen" button
  				case 58: case 59: case 66: case 86: case 190: case 191: togglePause(); break;
  				// f
  				case 70: enterFullscreen(); break;
  				// a
  				case 65: if ( config.autoSlideStoppable ) toggleAutoSlide( autoSlideWasPaused ); break;
  				default:
  					triggered = false;
  			}
  
  		}
  
  		// If the input resulted in a triggered action we should prevent
  		// the browsers default behavior
  		if( triggered ) {
  			event.preventDefault && event.preventDefault();
  		}
  		// ESC or O key
  		else if ( ( event.keyCode === 27 || event.keyCode === 79 ) && features.transforms3d ) {
  			if( dom.overlay ) {
  				closeOverlay();
  			}
  			else {
  				toggleOverview();
  			}
  
  			event.preventDefault && event.preventDefault();
  		}
  
  		// If auto-sliding is enabled we need to cue up
  		// another timeout
  		cueAutoSlide();
  
  	}
  
  	/**
  	 * Handler for the 'touchstart' event, enables support for
  	 * swipe and pinch gestures.
  	 *
  	 * @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;
  
  		// If there's two touches we need to memorize the distance
  		// between those two points to detect pinching
  		if( event.touches.length === 2 && config.overview ) {
  			touch.startSpan = distanceBetween( {
  				x: event.touches[1].clientX,
  				y: event.touches[1].clientY
  			}, {
  				x: touch.startX,
  				y: touch.startY
  			} );
  		}
  
  	}
  
  	/**
  	 * Handler for the 'touchmove' event.
  	 *
  	 * @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;
  
  			// If the touch started with two points and still has
  			// two active touches; test for the pinch gesture
  			if( event.touches.length === 2 && touch.startCount === 2 && config.overview ) {
  
  				// The current distance in pixels between the two touch points
  				var currentSpan = distanceBetween( {
  					x: event.touches[1].clientX,
  					y: event.touches[1].clientY
  				}, {
  					x: touch.startX,
  					y: touch.startY
  				} );
  
  				// If the span is larger than the desire amount we've got
  				// ourselves a pinch
  				if( Math.abs( touch.startSpan - currentSpan ) > touch.threshold ) {
  					touch.captured = true;
  
  					if( currentSpan < touch.startSpan ) {
  						activateOverview();
  					}
  					else {
  						deactivateOverview();
  					}
  				}
  
  				event.preventDefault();
  
  			}
  			// There was only one touch point, look for a swipe
  			else if( event.touches.length === 1 && touch.startCount !== 2 ) {
  
  				var deltaX = currentX - touch.startX,
  					deltaY = currentY - touch.startY;
  
  				if( deltaX > touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
  					touch.captured = true;
  					navigateLeft();
  				}
  				else if( deltaX < -touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
  					touch.captured = true;
  					navigateRight();
  				}
  				else if( deltaY > touch.threshold ) {
  					touch.captured = true;
  					navigateUp();
  				}
  				else if( deltaY < -touch.threshold ) {
  					touch.captured = true;
  					navigateDown();
  				}
  
  				// If we're embedded, only block touch events if they have
  				// triggered an action
  				if( config.embedded ) {
  					if( touch.captured || isVerticalSlide( currentSlide ) ) {
  						event.preventDefault();
  					}
  				}
  				// Not embedded? Block them all to avoid needless tossing
  				// around of the viewport in iOS
  				else {
  					event.preventDefault();
  				}
  
  			}
  		}
  		// There's a bug with swiping on some Android devices unless
  		// the default action is always prevented
  		else if( 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(); navigateLeft(); }
  	function onNavigateRightClicked( event ) { event.preventDefault(); onUserInput(); navigateRight(); }
  	function onNavigateUpClicked( event ) { event.preventDefault(); onUserInput(); navigateUp(); }
  	function onNavigateDownClicked( event ) { event.preventDefault(); onUserInput(); navigateDown(); }
  	function onNavigatePrevClicked( event ) { event.preventDefault(); onUserInput(); navigatePrev(); }
  	function onNavigateNextClicked( event ) { event.preventDefault(); onUserInput(); navigateNext(); }
  
  	/**
  	 * Handler for the window level 'hashchange' event.
  	 *
  	 * @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,
  
  		// 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 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 true if we're currently on the first slide
  		isFirstSlide: function() {
  			return ( indexh === 0 && indexv === 0 );
  		},
  
  		// Returns true if we're currently on the last slide
  		isLastSlide: function() {
  			if( currentSlide ) {
  				// Does this slide has next a sibling?
  				if( currentSlide.nextElementSibling ) return false;
  
  				// If it's vertical, does its parent have a next sibling?
  				if( isVerticalSlide( currentSlide ) && currentSlide.parentNode.nextElementSibling ) return false;
  
  				return true;
  			}
  
  			return false;
  		},
  
  		// Checks if reveal.js has been loaded and is ready for use
  		isReady: function() {
  			return loaded;
  		},
  
  		// Forward event binding to the reveal DOM element
  		addEventListener: function( type, listener, useCapture ) {
  			if( 'addEventListener' in window ) {
  				( dom.wrapper || document.querySelector( '.reveal' ) ).addEventListener( type, listener, useCapture );
  			}
  		},
  		removeEventListener: function( type, listener, useCapture ) {
  			if( 'addEventListener' in window ) {
  				( dom.wrapper || document.querySelector( '.reveal' ) ).removeEventListener( type, listener, useCapture );
  			}
  		},
  
  		// Programatically triggers a keyboard event
  		triggerKey: function( keyCode ) {
  			onDocumentKeyDown( { keyCode: keyCode } );
  		},
  
  		// Registers a new shortcut to include in the help overlay
  		registerKeyboardShortcut: function( key, value ) {
  			keyboardShortcuts[key] = value;
  		}
  	};
  
  	return Reveal;
  
  }));
  