diff --git a/inst/reveal.js-4.6.1/js/reveal.js b/inst/reveal.js-4.6.1/js/reveal.js
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index 0000000..1d19116
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+++ b/inst/reveal.js-4.6.1/js/reveal.js
@@ -0,0 +1,2840 @@
+import SlideContent from './controllers/slidecontent.js'
+import SlideNumber from './controllers/slidenumber.js'
+import JumpToSlide from './controllers/jumptoslide.js'
+import Backgrounds from './controllers/backgrounds.js'
+import AutoAnimate from './controllers/autoanimate.js'
+import Fragments from './controllers/fragments.js'
+import Overview from './controllers/overview.js'
+import Keyboard from './controllers/keyboard.js'
+import Location from './controllers/location.js'
+import Controls from './controllers/controls.js'
+import Progress from './controllers/progress.js'
+import Pointer from './controllers/pointer.js'
+import Plugins from './controllers/plugins.js'
+import Print from './controllers/print.js'
+import Touch from './controllers/touch.js'
+import Focus from './controllers/focus.js'
+import Notes from './controllers/notes.js'
+import Playback from './components/playback.js'
+import defaultConfig from './config.js'
+import * as Util from './utils/util.js'
+import * as Device from './utils/device.js'
+import {
+	SLIDES_SELECTOR,
+	HORIZONTAL_SLIDES_SELECTOR,
+	VERTICAL_SLIDES_SELECTOR,
+	POST_MESSAGE_METHOD_BLACKLIST
+} from './utils/constants.js'
+
+// The reveal.js version
+export const VERSION = '4.6.0';
+
+/**
+ * reveal.js
+ * https://revealjs.com
+ * MIT licensed
+ *
+ * Copyright (C) 2011-2022 Hakim El Hattab, https://hakim.se
+ */
+export default function( revealElement, options ) {
+
+	// Support initialization with no args, one arg
+	// [options] or two args [revealElement, options]
+	if( arguments.length < 2 ) {
+		options = arguments[0];
+		revealElement = document.querySelector( '.reveal' );
+	}
+
+	const Reveal = {};
+
+	// Configuration defaults, can be overridden at initialization time
+	let config = {},
+
+		// Flags if reveal.js is loaded (has dispatched the 'ready' event)
+		ready = false,
+
+		// The horizontal and vertical index of the currently active slide
+		indexh,
+		indexv,
+
+		// The previous and current slide HTML elements
+		previousSlide,
+		currentSlide,
+
+		// Remember which directions that the user has navigated towards
+		navigationHistory = {
+			hasNavigatedHorizontally: false,
+			hasNavigatedVertically: false
+		},
+
+		// Slides may have 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 = {},
+
+		// Flags if the interaction event listeners are bound
+		eventsAreBound = false,
+
+		// The current slide transition state; idle or running
+		transition = 'idle',
+
+		// The current auto-slide duration
+		autoSlide = 0,
+
+		// Auto slide properties
+		autoSlidePlayer,
+		autoSlideTimeout = 0,
+		autoSlideStartTime = -1,
+		autoSlidePaused = false,
+
+		// Controllers for different aspects of our presentation. They're
+		// all given direct references to this Reveal instance since there
+		// may be multiple presentations running in parallel.
+		slideContent = new SlideContent( Reveal ),
+		slideNumber = new SlideNumber( Reveal ),
+		jumpToSlide = new JumpToSlide( Reveal ),
+		autoAnimate = new AutoAnimate( Reveal ),
+		backgrounds = new Backgrounds( Reveal ),
+		fragments = new Fragments( Reveal ),
+		overview = new Overview( Reveal ),
+		keyboard = new Keyboard( Reveal ),
+		location = new Location( Reveal ),
+		controls = new Controls( Reveal ),
+		progress = new Progress( Reveal ),
+		pointer = new Pointer( Reveal ),
+		plugins = new Plugins( Reveal ),
+		print = new Print( Reveal ),
+		focus = new Focus( Reveal ),
+		touch = new Touch( Reveal ),
+		notes = new Notes( Reveal );
+
+	/**
+	 * Starts up the presentation.
+	 */
+	function initialize( initOptions ) {
+
+		if( !revealElement ) throw 'Unable to find presentation root (<div class="reveal">).';
+
+		// Cache references to key DOM elements
+		dom.wrapper = revealElement;
+		dom.slides = revealElement.querySelector( '.slides' );
+
+		if( !dom.slides ) throw 'Unable to find slides container (<div class="slides">).';
+
+		// Compose our config object in order of increasing precedence:
+		// 1. Default reveal.js options
+		// 2. Options provided via Reveal.configure() prior to
+		//    initialization
+		// 3. Options passed to the Reveal constructor
+		// 4. Options passed to Reveal.initialize
+		// 5. Query params
+		config = { ...defaultConfig, ...config, ...options, ...initOptions, ...Util.getQueryHash() };
+
+		setViewport();
+
+		// Force a layout when the whole page, incl fonts, has loaded
+		window.addEventListener( 'load', layout, false );
+
+		// Register plugins and load dependencies, then move on to #start()
+		plugins.load( config.plugins, config.dependencies ).then( start );
+
+		return new Promise( resolve => Reveal.on( 'ready', resolve ) );
+
+	}
+
+	/**
+	 * Encase the presentation in a reveal.js viewport. The
+	 * extent of the viewport differs based on configuration.
+	 */
+	function setViewport() {
+
+		// Embedded decks use the reveal element as their viewport
+		if( config.embedded === true ) {
+			dom.viewport = Util.closest( revealElement, '.reveal-viewport' ) || revealElement;
+		}
+		// Full-page decks use the body as their viewport
+		else {
+			dom.viewport = document.body;
+			document.documentElement.classList.add( 'reveal-full-page' );
+		}
+
+		dom.viewport.classList.add( 'reveal-viewport' );
+
+	}
+
+	/**
+	 * Starts up reveal.js by binding input events and navigating
+	 * to the current URL deeplink if there is one.
+	 */
+	function start() {
+
+		ready = true;
+
+		// Remove slides hidden with data-visibility
+		removeHiddenSlides();
+
+		// 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();
+
+		// Adds bindings for fullscreen mode
+		setupFullscreen();
+
+		// 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
+		location.readURL();
+
+		// Create slide backgrounds
+		backgrounds.update( true );
+
+		// Notify listeners that the presentation is ready but use a 1ms
+		// timeout to ensure it's not fired synchronously after #initialize()
+		setTimeout( () => {
+			// Enable transitions now that we're loaded
+			dom.slides.classList.remove( 'no-transition' );
+
+			dom.wrapper.classList.add( 'ready' );
+
+			dispatchEvent({
+				type: 'ready',
+				data: {
+					indexh,
+					indexv,
+					currentSlide
+				}
+			});
+		}, 1 );
+
+		// Special setup and config is required when printing to PDF
+		if( print.isPrintingPDF() ) {
+			removeEventListeners();
+
+			// The document needs to have loaded for the PDF layout
+			// measurements to be accurate
+			if( document.readyState === 'complete' ) {
+				print.setupPDF();
+			}
+			else {
+				window.addEventListener( 'load', () => {
+					print.setupPDF();
+				} );
+			}
+		}
+
+	}
+
+	/**
+	 * Removes all slides with data-visibility="hidden". This
+	 * is done right before the rest of the presentation is
+	 * initialized.
+	 *
+	 * If you want to show all hidden slides, initialize
+	 * reveal.js with showHiddenSlides set to true.
+	 */
+	function removeHiddenSlides() {
+
+		if( !config.showHiddenSlides ) {
+			Util.queryAll( dom.wrapper, 'section[data-visibility="hidden"]' ).forEach( slide => {
+				slide.parentNode.removeChild( slide );
+			} );
+		}
+
+	}
+
+	/**
+	 * 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( Device.isMobile ) {
+			dom.wrapper.classList.add( 'no-hover' );
+		}
+		else {
+			dom.wrapper.classList.remove( 'no-hover' );
+		}
+
+		backgrounds.render();
+		slideNumber.render();
+		jumpToSlide.render();
+		controls.render();
+		progress.render();
+		notes.render();
+
+		// Overlay graphic which is displayed during the paused mode
+		dom.pauseOverlay = Util.createSingletonNode( dom.wrapper, 'div', 'pause-overlay', config.controls ? '<button class="resume-button">Resume presentation</button>' : null );
+
+		dom.statusElement = createStatusElement();
+
+		dom.wrapper.setAttribute( 'role', 'application' );
+	}
+
+	/**
+	 * 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 createStatusElement() {
+
+		let statusElement = dom.wrapper.querySelector( '.aria-status' );
+		if( !statusElement ) {
+			statusElement = document.createElement( 'div' );
+			statusElement.style.position = 'absolute';
+			statusElement.style.height = '1px';
+			statusElement.style.width = '1px';
+			statusElement.style.overflow = 'hidden';
+			statusElement.style.clip = 'rect( 1px, 1px, 1px, 1px )';
+			statusElement.classList.add( 'aria-status' );
+			statusElement.setAttribute( 'aria-live', 'polite' );
+			statusElement.setAttribute( 'aria-atomic','true' );
+			dom.wrapper.appendChild( statusElement );
+		}
+		return statusElement;
+
+	}
+
+	/**
+	 * Announces the given text to screen readers.
+	 */
+	function announceStatus( value ) {
+
+		dom.statusElement.textContent = value;
+
+	}
+
+	/**
+	 * 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 ) {
+
+		let text = '';
+
+		// Text node
+		if( node.nodeType === 3 ) {
+			text += node.textContent;
+		}
+		// Element node
+		else if( node.nodeType === 1 ) {
+
+			let isAriaHidden = node.getAttribute( 'aria-hidden' );
+			let isDisplayHidden = window.getComputedStyle( node )['display'] === 'none';
+			if( isAriaHidden !== 'true' && !isDisplayHidden ) {
+
+				Array.from( node.childNodes ).forEach( child => {
+					text += getStatusText( child );
+				} );
+
+			}
+
+		}
+
+		text = text.trim();
+
+		return text === '' ? '' : text + ' ';
+
+	}
+
+	/**
+	 * 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( () => {
+			if( dom.wrapper.scrollTop !== 0 || dom.wrapper.scrollLeft !== 0 ) {
+				dom.wrapper.scrollTop = 0;
+				dom.wrapper.scrollLeft = 0;
+			}
+		}, 1000 );
+
+	}
+
+	/**
+	 * After entering fullscreen we need to force a layout to
+	 * get our presentations to scale correctly. This behavior
+	 * is inconsistent across browsers but a force layout seems
+	 * to normalize it.
+	 */
+	function setupFullscreen() {
+
+		document.addEventListener( 'fullscreenchange', onFullscreenChange );
+		document.addEventListener( 'webkitfullscreenchange', onFullscreenChange );
+
+	}
+
+	/**
+	 * 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', onPostMessage, false );
+		}
+
+	}
+
+	/**
+	 * Applies the configuration settings from the config
+	 * object. May be called multiple times.
+	 *
+	 * @param {object} options
+	 */
+	function configure( options ) {
+
+		const oldConfig = { ...config }
+
+		// New config options may be passed when this method
+		// is invoked through the API after initialization
+		if( typeof options === 'object' ) Util.extend( config, options );
+
+		// Abort if reveal.js hasn't finished loading, config
+		// changes will be applied automatically once ready
+		if( Reveal.isReady() ===  false ) return;
+
+		const numberOfSlides = dom.wrapper.querySelectorAll( SLIDES_SELECTOR ).length;
+
+		// The transition is added as a class on the .reveal element
+		dom.wrapper.classList.remove( oldConfig.transition );
+		dom.wrapper.classList.add( config.transition );
+
+		dom.wrapper.setAttribute( 'data-transition-speed', config.transitionSpeed );
+		dom.wrapper.setAttribute( 'data-background-transition', config.backgroundTransition );
+
+		// Expose our configured slide dimensions as custom props
+		dom.viewport.style.setProperty( '--slide-width', config.width + 'px' );
+		dom.viewport.style.setProperty( '--slide-height', config.height + 'px' );
+
+		if( config.shuffle ) {
+			shuffle();
+		}
+
+		Util.toggleClass( dom.wrapper, 'embedded', config.embedded );
+		Util.toggleClass( dom.wrapper, 'rtl', config.rtl );
+		Util.toggleClass( dom.wrapper, 'center', config.center );
+
+		// Exit the paused mode if it was configured off
+		if( config.pause === false ) {
+			resume();
+		}
+
+		// Iframe link previews
+		if( config.previewLinks ) {
+			enablePreviewLinks();
+			disablePreviewLinks( '[data-preview-link=false]' );
+		}
+		else {
+			disablePreviewLinks();
+			enablePreviewLinks( '[data-preview-link]:not([data-preview-link=false])' );
+		}
+
+		// Reset all changes made by auto-animations
+		autoAnimate.reset();
+
+		// Remove existing auto-slide controls
+		if( autoSlidePlayer ) {
+			autoSlidePlayer.destroy();
+			autoSlidePlayer = null;
+		}
+
+		// Generate auto-slide controls if needed
+		if( numberOfSlides > 1 && config.autoSlide && config.autoSlideStoppable ) {
+			autoSlidePlayer = new Playback( dom.wrapper, () => {
+				return Math.min( Math.max( ( Date.now() - autoSlideStartTime ) / autoSlide, 0 ), 1 );
+			} );
+
+			autoSlidePlayer.on( 'click', onAutoSlidePlayerClick );
+			autoSlidePaused = false;
+		}
+
+		// Add the navigation mode to the DOM so we can adjust styling
+		if( config.navigationMode !== 'default' ) {
+			dom.wrapper.setAttribute( 'data-navigation-mode', config.navigationMode );
+		}
+		else {
+			dom.wrapper.removeAttribute( 'data-navigation-mode' );
+		}
+
+		notes.configure( config, oldConfig );
+		focus.configure( config, oldConfig );
+		pointer.configure( config, oldConfig );
+		controls.configure( config, oldConfig );
+		progress.configure( config, oldConfig );
+		keyboard.configure( config, oldConfig );
+		fragments.configure( config, oldConfig );
+		slideNumber.configure( config, oldConfig );
+
+		sync();
+
+	}
+
+	/**
+	 * Binds all event listeners.
+	 */
+	function addEventListeners() {
+
+		eventsAreBound = true;
+
+		window.addEventListener( 'resize', onWindowResize, false );
+
+		if( config.touch ) touch.bind();
+		if( config.keyboard ) keyboard.bind();
+		if( config.progress ) progress.bind();
+		if( config.respondToHashChanges ) location.bind();
+		controls.bind();
+		focus.bind();
+
+		dom.slides.addEventListener( 'click', onSlidesClicked, false );
+		dom.slides.addEventListener( 'transitionend', onTransitionEnd, false );
+		dom.pauseOverlay.addEventListener( 'click', resume, false );
+
+		if( config.focusBodyOnPageVisibilityChange ) {
+			document.addEventListener( 'visibilitychange', onPageVisibilityChange, false );
+		}
+
+	}
+
+	/**
+	 * Unbinds all event listeners.
+	 */
+	function removeEventListeners() {
+
+		eventsAreBound = false;
+
+		touch.unbind();
+		focus.unbind();
+		keyboard.unbind();
+		controls.unbind();
+		progress.unbind();
+		location.unbind();
+
+		window.removeEventListener( 'resize', onWindowResize, false );
+
+		dom.slides.removeEventListener( 'click', onSlidesClicked, false );
+		dom.slides.removeEventListener( 'transitionend', onTransitionEnd, false );
+		dom.pauseOverlay.removeEventListener( 'click', resume, false );
+
+	}
+
+	/**
+	 * Uninitializes reveal.js by undoing changes made to the
+	 * DOM and removing all event listeners.
+	 */
+	function destroy() {
+
+		removeEventListeners();
+		cancelAutoSlide();
+		disablePreviewLinks();
+
+		// Destroy controllers
+		notes.destroy();
+		focus.destroy();
+		plugins.destroy();
+		pointer.destroy();
+		controls.destroy();
+		progress.destroy();
+		backgrounds.destroy();
+		slideNumber.destroy();
+		jumpToSlide.destroy();
+
+		// Remove event listeners
+		document.removeEventListener( 'fullscreenchange', onFullscreenChange );
+		document.removeEventListener( 'webkitfullscreenchange', onFullscreenChange );
+		document.removeEventListener( 'visibilitychange', onPageVisibilityChange, false );
+		window.removeEventListener( 'message', onPostMessage, false );
+		window.removeEventListener( 'load', layout, false );
+
+		// Undo DOM changes
+		if( dom.pauseOverlay ) dom.pauseOverlay.remove();
+		if( dom.statusElement ) dom.statusElement.remove();
+
+		document.documentElement.classList.remove( 'reveal-full-page' );
+
+		dom.wrapper.classList.remove( 'ready', 'center', 'has-horizontal-slides', 'has-vertical-slides' );
+		dom.wrapper.removeAttribute( 'data-transition-speed' );
+		dom.wrapper.removeAttribute( 'data-background-transition' );
+
+		dom.viewport.classList.remove( 'reveal-viewport' );
+		dom.viewport.style.removeProperty( '--slide-width' );
+		dom.viewport.style.removeProperty( '--slide-height' );
+
+		dom.slides.style.removeProperty( 'width' );
+		dom.slides.style.removeProperty( 'height' );
+		dom.slides.style.removeProperty( 'zoom' );
+		dom.slides.style.removeProperty( 'left' );
+		dom.slides.style.removeProperty( 'top' );
+		dom.slides.style.removeProperty( 'bottom' );
+		dom.slides.style.removeProperty( 'right' );
+		dom.slides.style.removeProperty( 'transform' );
+
+		Array.from( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) ).forEach( slide => {
+			slide.style.removeProperty( 'display' );
+			slide.style.removeProperty( 'top' );
+			slide.removeAttribute( 'hidden' );
+			slide.removeAttribute( 'aria-hidden' );
+		} );
+
+	}
+
+	/**
+	 * Adds a listener to one of our custom reveal.js events,
+	 * like slidechanged.
+	 */
+	function on( type, listener, useCapture ) {
+
+		revealElement.addEventListener( type, listener, useCapture );
+
+	}
+
+	/**
+	 * Unsubscribes from a reveal.js event.
+	 */
+	function off( type, listener, useCapture ) {
+
+		revealElement.removeEventListener( type, listener, useCapture );
+
+	}
+
+	/**
+	 * 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 ) {
+			Util.transformElement( dom.slides, slidesTransform.layout + ' ' + slidesTransform.overview );
+		}
+		else {
+			Util.transformElement( dom.slides, slidesTransform.overview );
+		}
+
+	}
+
+	/**
+	 * Dispatches an event of the specified type from the
+	 * reveal DOM element.
+	 */
+	function dispatchEvent({ target=dom.wrapper, type, data, bubbles=true }) {
+
+		let event = document.createEvent( 'HTMLEvents', 1, 2 );
+		event.initEvent( type, bubbles, true );
+		Util.extend( event, data );
+		target.dispatchEvent( event );
+
+		if( target === dom.wrapper ) {
+			// If we're in an iframe, post each reveal.js event to the
+			// parent window. Used by the notes plugin
+			dispatchPostMessage( type );
+		}
+
+		return event;
+
+	}
+
+	/**
+	 * Dispatched a postMessage of the given type from our window.
+	 */
+	function dispatchPostMessage( type, data ) {
+
+		if( config.postMessageEvents && window.parent !== window.self ) {
+			let message = {
+				namespace: 'reveal',
+				eventName: type,
+				state: getState()
+			};
+
+			Util.extend( message, data );
+
+			window.parent.postMessage( JSON.stringify( message ), '*' );
+		}
+
+	}
+
+	/**
+	 * Bind preview frame links.
+	 *
+	 * @param {string} [selector=a] - selector for anchors
+	 */
+	function enablePreviewLinks( selector = 'a' ) {
+
+		Array.from( dom.wrapper.querySelectorAll( selector ) ).forEach( element => {
+			if( /^(http|www)/gi.test( element.getAttribute( 'href' ) ) ) {
+				element.addEventListener( 'click', onPreviewLinkClicked, false );
+			}
+		} );
+
+	}
+
+	/**
+	 * Unbind preview frame links.
+	 */
+	function disablePreviewLinks( selector = 'a' ) {
+
+		Array.from( dom.wrapper.querySelectorAll( selector ) ).forEach( 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>`;
+
+		dom.overlay.querySelector( 'iframe' ).addEventListener( 'load', event => {
+			dom.overlay.classList.add( 'loaded' );
+		}, false );
+
+		dom.overlay.querySelector( '.close' ).addEventListener( 'click', event => {
+			closeOverlay();
+			event.preventDefault();
+		}, false );
+
+		dom.overlay.querySelector( '.external' ).addEventListener( 'click', event => {
+			closeOverlay();
+		}, false );
+
+	}
+
+	/**
+	 * 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 );
+
+			let html = '<p class="title">Keyboard Shortcuts</p><br/>';
+
+			let shortcuts = keyboard.getShortcuts(),
+				bindings = keyboard.getBindings();
+
+			html += '<table><th>KEY</th><th>ACTION</th>';
+			for( let key in shortcuts ) {
+				html += `<tr><td>${key}</td><td>${shortcuts[ key ]}</td></tr>`;
+			}
+
+			// Add custom key bindings that have associated descriptions
+			for( let binding in bindings ) {
+				if( bindings[binding].key && bindings[binding].description ) {
+					html += `<tr><td>${bindings[binding].key}</td><td>${bindings[binding].description}</td></tr>`;
+				}
+			}
+
+			html += '</table>';
+
+			dom.overlay.innerHTML = `
+				<header>
+					<a class="close" href="#"><span class="icon"></span></a>
+				</header>
+				<div class="viewport">
+					<div class="viewport-inner">${html}</div>
+				</div>
+			`;
+
+			dom.overlay.querySelector( '.close' ).addEventListener( 'click', event => {
+				closeOverlay();
+				event.preventDefault();
+			}, false );
+
+		}
+
+	}
+
+	/**
+	 * Closes any currently open overlay.
+	 */
+	function closeOverlay() {
+
+		if( dom.overlay ) {
+			dom.overlay.parentNode.removeChild( dom.overlay );
+			dom.overlay = null;
+			return true;
+		}
+
+		return false;
+
+	}
+
+	/**
+	 * Applies JavaScript-controlled layout rules to the
+	 * presentation.
+	 */
+	function layout() {
+
+		if( dom.wrapper && !print.isPrintingPDF() ) {
+
+			if( !config.disableLayout ) {
+
+				// On some mobile devices '100vh' is taller than the visible
+				// viewport which leads to part of the presentation being
+				// cut off. To work around this we define our own '--vh' custom
+				// property where 100x adds up to the correct height.
+				//
+				// https://css-tricks.com/the-trick-to-viewport-units-on-mobile/
+				if( Device.isMobile && !config.embedded ) {
+					document.documentElement.style.setProperty( '--vh', ( window.innerHeight * 0.01 ) + 'px' );
+				}
+
+				const size = getComputedSlideSize();
+
+				const oldScale = scale;
+
+				// Layout the contents of the slides
+				layoutSlideContents( config.width, config.height );
+
+				dom.slides.style.width = size.width + 'px';
+				dom.slides.style.height = size.height + 'px';
+
+				// Determine scale of content to fit within available space
+				scale = Math.min( size.presentationWidth / size.width, size.presentationHeight / size.height );
+
+				// Respect max/min scale settings
+				scale = Math.max( scale, config.minScale );
+				scale = Math.min( scale, config.maxScale );
+
+				// Don't apply any scaling styles if scale is 1
+				if( scale === 1 ) {
+					dom.slides.style.zoom = '';
+					dom.slides.style.left = '';
+					dom.slides.style.top = '';
+					dom.slides.style.bottom = '';
+					dom.slides.style.right = '';
+					transformSlides( { layout: '' } );
+				}
+				else {
+					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
+				const slides = Array.from( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) );
+
+				for( let i = 0, len = slides.length; i < len; i++ ) {
+					const slide = slides[ i ];
+
+					// Don't bother updating invisible slides
+					if( slide.style.display === 'none' ) {
+						continue;
+					}
+
+					if( config.center || slide.classList.contains( 'center' ) ) {
+						// Vertical stacks are not centred since their section
+						// children will be
+						if( slide.classList.contains( 'stack' ) ) {
+							slide.style.top = 0;
+						}
+						else {
+							slide.style.top = Math.max( ( size.height - slide.scrollHeight ) / 2, 0 ) + 'px';
+						}
+					}
+					else {
+						slide.style.top = '';
+					}
+
+				}
+
+				if( oldScale !== scale ) {
+					dispatchEvent({
+						type: 'resize',
+						data: {
+							oldScale,
+							scale,
+							size
+						}
+					});
+				}
+			}
+
+			dom.viewport.style.setProperty( '--slide-scale', scale );
+
+			progress.update();
+			backgrounds.updateParallax();
+
+			if( overview.isActive() ) {
+				overview.update();
+			}
+
+		}
+
+	}
+
+	/**
+	 * 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 'r-stretch' class
+		Util.queryAll( dom.slides, 'section > .stretch, section > .r-stretch' ).forEach( element => {
+
+			// Determine how much vertical space we can use
+			let remainingHeight = Util.getRemainingHeight( element, height );
+
+			// Consider the aspect ratio of media elements
+			if( /(img|video)/gi.test( element.nodeName ) ) {
+				const nw = element.naturalWidth || element.videoWidth,
+					  nh = element.naturalHeight || element.videoHeight;
+
+				const 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 ) {
+		let width = config.width;
+		let height = config.height;
+
+		if( config.disableLayout ) {
+			width = dom.slides.offsetWidth;
+			height = dom.slides.offsetHeight;
+		}
+
+		const size = {
+			// Slide size
+			width: width,
+			height: 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
+			const attributeName = stack.hasAttribute( 'data-start-indexv' ) ? 'data-start-indexv' : 'data-previous-indexv';
+
+			return parseInt( stack.getAttribute( attributeName ) || 0, 10 );
+		}
+
+		return 0;
+
+	}
+
+	/**
+	 * 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 = currentSlide ) {
+
+		return slide && slide.parentNode && !!slide.parentNode.nodeName.match( /section/i );
+
+	}
+
+	/**
+	 * Returns true if we're on the last slide in the current
+	 * vertical stack.
+	 */
+	function isLastVerticalSlide() {
+
+		if( currentSlide && isVerticalSlide( currentSlide ) ) {
+			// Does this slide have a next sibling?
+			if( currentSlide.nextElementSibling ) return false;
+
+			return true;
+		}
+
+		return false;
+
+	}
+
+	/**
+	 * Returns true if we're currently on the first slide in
+	 * the presentation.
+	 */
+	function isFirstSlide() {
+
+		return indexh === 0 && indexv === 0;
+
+	}
+
+	/**
+	 * Returns true if we're currently on the last slide in
+	 * the presenation. If the last slide is a stack, we only
+	 * consider this the last slide if it's at the end of the
+	 * stack.
+	 */
+	function isLastSlide() {
+
+		if( currentSlide ) {
+			// Does this slide have a next sibling?
+			if( currentSlide.nextElementSibling ) return false;
+
+			// If it's vertical, does its parent have a next sibling?
+			if( isVerticalSlide( currentSlide ) && currentSlide.parentNode.nextElementSibling ) return false;
+
+			return true;
+		}
+
+		return false;
+
+	}
+
+	/**
+	 * Enters the paused mode which fades everything on screen to
+	 * black.
+	 */
+	function pause() {
+
+		if( config.pause ) {
+			const wasPaused = dom.wrapper.classList.contains( 'paused' );
+
+			cancelAutoSlide();
+			dom.wrapper.classList.add( 'paused' );
+
+			if( wasPaused === false ) {
+				dispatchEvent({ type: 'paused' });
+			}
+		}
+
+	}
+
+	/**
+	 * Exits from the paused mode.
+	 */
+	function resume() {
+
+		const wasPaused = dom.wrapper.classList.contains( 'paused' );
+		dom.wrapper.classList.remove( 'paused' );
+
+		cueAutoSlide();
+
+		if( wasPaused ) {
+			dispatchEvent({ type: '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 visibility of the jump-to-slide UI.
+	 */
+	function toggleJumpToSlide( override ) {
+
+		if( typeof override === 'boolean' ) {
+			override ? jumpToSlide.show() : jumpToSlide.hide();
+		}
+		else {
+			jumpToSlide.isVisible() ? jumpToSlide.hide() : jumpToSlide.show();
+		}
+
+	}
+
+	/**
+	 * 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} [origin] Origin for use in multimaster environments
+	 */
+	function slide( h, v, f, origin ) {
+
+		// Dispatch an event before the slide
+		const slidechange = dispatchEvent({
+			type: 'beforeslidechange',
+			data: {
+				indexh: h === undefined ? indexh : h,
+				indexv: v === undefined ? indexv : v,
+				origin
+			}
+		});
+
+		// Abort if this slide change was prevented by an event listener
+		if( slidechange.defaultPrevented ) return;
+
+		// Remember where we were at before
+		previousSlide = currentSlide;
+
+		// Query all horizontal slides in the deck
+		const 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 && !overview.isActive() ) {
+			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
+		const stateBefore = state.concat();
+
+		// Reset the state array
+		state.length = 0;
+
+		let 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 );
+
+		// Dispatch an event if the slide changed
+		let slideChanged = ( indexh !== indexhBefore || indexv !== indexvBefore );
+
+		// Ensure that the previous slide is never the same as the current
+		if( !slideChanged ) previousSlide = null;
+
+		// Find the current horizontal slide and any possible vertical slides
+		// within it
+		let currentHorizontalSlide = horizontalSlides[ indexh ],
+			currentVerticalSlides = currentHorizontalSlide.querySelectorAll( 'section' );
+
+		// Store references to the previous and current slides
+		currentSlide = currentVerticalSlides[ indexv ] || currentHorizontalSlide;
+
+		let autoAnimateTransition = false;
+
+		// Detect if we're moving between two auto-animated slides
+		if( slideChanged && previousSlide && currentSlide && !overview.isActive() ) {
+
+			// If this is an auto-animated transition, we disable the
+			// regular slide transition
+			//
+			// Note 20-03-2020:
+			// This needs to happen before we update slide visibility,
+			// otherwise transitions will still run in Safari.
+			if( previousSlide.hasAttribute( 'data-auto-animate' ) && currentSlide.hasAttribute( 'data-auto-animate' )
+					&& previousSlide.getAttribute( 'data-auto-animate-id' ) === currentSlide.getAttribute( 'data-auto-animate-id' )
+					&& !( ( indexh > indexhBefore || indexv > indexvBefore ) ? currentSlide : previousSlide ).hasAttribute( 'data-auto-animate-restart' ) ) {
+
+				autoAnimateTransition = true;
+				dom.slides.classList.add( 'disable-slide-transitions' );
+			}
+
+			transition = 'running';
+
+		}
+
+		// Update the visibility of slides now that the indices have changed
+		updateSlidesVisibility();
+
+		layout();
+
+		// Update the overview if it's currently active
+		if( overview.isActive() ) {
+			overview.update();
+		}
+
+		// Show fragment, if specified
+		if( typeof f !== 'undefined' ) {
+			fragments.goto( f );
+		}
+
+		// Solves an edge case where the previous slide maintains the
+		// 'present' class when navigating between adjacent vertical
+		// stacks
+		if( previousSlide && previousSlide !== currentSlide ) {
+			previousSlide.classList.remove( 'present' );
+			previousSlide.setAttribute( 'aria-hidden', 'true' );
+
+			// Reset all slides upon navigate to home
+			if( isFirstSlide() ) {
+				// Launch async task
+				setTimeout( () => {
+					getVerticalStacks().forEach( slide => {
+						setPreviousVerticalIndex( slide, 0 );
+					} );
+				}, 0 );
+			}
+		}
+
+		// Apply the new state
+		stateLoop: for( let 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( let j = 0; j < stateBefore.length; j++ ) {
+				if( stateBefore[j] === state[i] ) {
+					stateBefore.splice( j, 1 );
+					continue stateLoop;
+				}
+			}
+
+			dom.viewport.classList.add( state[i] );
+
+			// Dispatch custom event matching the state's name
+			dispatchEvent({ type: state[i] });
+		}
+
+		// Clean up the remains of the previous state
+		while( stateBefore.length ) {
+			dom.viewport.classList.remove( stateBefore.pop() );
+		}
+
+		if( slideChanged ) {
+			dispatchEvent({
+				type: 'slidechanged',
+				data: {
+					indexh,
+					indexv,
+					previousSlide,
+					currentSlide,
+					origin
+				}
+			});
+		}
+
+		// Handle embedded content
+		if( slideChanged || !previousSlide ) {
+			slideContent.stopEmbeddedContent( previousSlide );
+			slideContent.startEmbeddedContent( currentSlide );
+		}
+
+		// Announce the current slide contents to screen readers
+		// Use animation frame to prevent getComputedStyle in getStatusText
+		// from triggering layout mid-frame
+		requestAnimationFrame( () => {
+			announceStatus( getStatusText( currentSlide ) );
+		});
+
+		progress.update();
+		controls.update();
+		notes.update();
+		backgrounds.update();
+		backgrounds.updateParallax();
+		slideNumber.update();
+		fragments.update();
+
+		// Update the URL hash
+		location.writeURL();
+
+		cueAutoSlide();
+
+		// Auto-animation
+		if( autoAnimateTransition ) {
+
+			setTimeout( () => {
+				dom.slides.classList.remove( 'disable-slide-transitions' );
+			}, 0 );
+
+			if( config.autoAnimate ) {
+				// Run the auto-animation between our slides
+				autoAnimate.run( previousSlide, currentSlide );
+			}
+
+		}
+
+	}
+
+	/**
+	 * 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 all slide backgrounds
+		backgrounds.create();
+
+		// Write the current hash to the URL
+		location.writeURL();
+
+		if( config.sortFragmentsOnSync === true ) {
+			fragments.sortAll();
+		}
+
+		controls.update();
+		progress.update();
+
+		updateSlidesVisibility();
+
+		notes.update();
+		notes.updateVisibility();
+		backgrounds.update( true );
+		slideNumber.update();
+		slideContent.formatEmbeddedContent();
+
+		// Start or stop embedded content depending on global config
+		if( config.autoPlayMedia === false ) {
+			slideContent.stopEmbeddedContent( currentSlide, { unloadIframes: false } );
+		}
+		else {
+			slideContent.startEmbeddedContent( currentSlide );
+		}
+
+		if( overview.isActive() ) {
+			overview.layout();
+		}
+
+	}
+
+	/**
+	 * Updates reveal.js to keep in sync with new slide attributes. For
+	 * example, if you add a new `data-background-image` you can call
+	 * this to have reveal.js render the new background image.
+	 *
+	 * Similar to #sync() but more efficient when you only need to
+	 * refresh a specific slide.
+	 *
+	 * @param {HTMLElement} slide
+	 */
+	function syncSlide( slide = currentSlide ) {
+
+		backgrounds.sync( slide );
+		fragments.sync( slide );
+
+		slideContent.load( slide );
+
+		backgrounds.update();
+		notes.update();
+
+	}
+
+	/**
+	 * Resets all vertical slides so that only the first
+	 * is visible.
+	 */
+	function resetVerticalSlides() {
+
+		getHorizontalSlides().forEach( horizontalSlide => {
+
+			Util.queryAll( horizontalSlide, 'section' ).forEach( ( verticalSlide, y ) => {
+
+				if( y > 0 ) {
+					verticalSlide.classList.remove( 'present' );
+					verticalSlide.classList.remove( 'past' );
+					verticalSlide.classList.add( 'future' );
+					verticalSlide.setAttribute( 'aria-hidden', 'true' );
+				}
+
+			} );
+
+		} );
+
+	}
+
+	/**
+	 * Randomly shuffles all slides in the deck.
+	 */
+	function shuffle( slides = getHorizontalSlides() ) {
+
+		slides.forEach( ( slide, i ) => {
+
+			// Insert the slide next to a randomly picked sibling slide
+			// slide. This may cause the slide to insert before itself,
+			// but that's not an issue.
+			let beforeSlide = slides[ Math.floor( Math.random() * slides.length ) ];
+			if( beforeSlide.parentNode === slide.parentNode ) {
+				slide.parentNode.insertBefore( slide, beforeSlide );
+			}
+
+			// Randomize the order of vertical slides (if there are any)
+			let verticalSlides = slide.querySelectorAll( 'section' );
+			if( verticalSlides.length ) {
+				shuffle( verticalSlides );
+			}
+
+		} );
+
+	}
+
+	/**
+	 * 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
+		let slides = Util.queryAll( dom.wrapper, selector ),
+			slidesLength = slides.length;
+
+		let printMode = print.isPrintingPDF();
+		let loopedForwards = false;
+		let loopedBackwards = false;
+
+		if( slidesLength ) {
+
+			// Should the index loop?
+			if( config.loop ) {
+				if( index >= slidesLength ) loopedForwards = true;
+
+				index %= slidesLength;
+
+				if( index < 0 ) {
+					index = slidesLength + index;
+					loopedBackwards = true;
+				}
+			}
+
+			// Enforce max and minimum index bounds
+			index = Math.max( Math.min( index, slidesLength - 1 ), 0 );
+
+			for( let i = 0; i < slidesLength; i++ ) {
+				let element = slides[i];
+
+				let reverse = config.rtl && !isVerticalSlide( element );
+
+				// Avoid .remove() with multiple args for IE11 support
+				element.classList.remove( 'past' );
+				element.classList.remove( 'present' );
+				element.classList.remove( 'future' );
+
+				// http://www.w3.org/html/wg/drafts/html/master/editing.html#the-hidden-attribute
+				element.setAttribute( 'hidden', '' );
+				element.setAttribute( 'aria-hidden', 'true' );
+
+				// If this element contains vertical slides
+				if( element.querySelector( 'section' ) ) {
+					element.classList.add( 'stack' );
+				}
+
+				// If we're printing static slides, all slides are "present"
+				if( printMode ) {
+					element.classList.add( 'present' );
+					continue;
+				}
+
+				if( i < index ) {
+					// Any element previous to index is given the 'past' class
+					element.classList.add( reverse ? 'future' : 'past' );
+
+					if( config.fragments ) {
+						// Show all fragments in prior slides
+						showFragmentsIn( element );
+					}
+				}
+				else if( i > index ) {
+					// Any element subsequent to index is given the 'future' class
+					element.classList.add( reverse ? 'past' : 'future' );
+
+					if( config.fragments ) {
+						// Hide all fragments in future slides
+						hideFragmentsIn( element );
+					}
+				}
+				// Update the visibility of fragments when a presentation loops
+				// in either direction
+				else if( i === index && config.fragments ) {
+					if( loopedForwards ) {
+						hideFragmentsIn( element );
+					}
+					else if( loopedBackwards ) {
+						showFragmentsIn( element );
+					}
+				}
+			}
+
+			let slide = slides[index];
+			let wasPresent = slide.classList.contains( 'present' );
+
+			// Mark the current slide as present
+			slide.classList.add( 'present' );
+			slide.removeAttribute( 'hidden' );
+			slide.removeAttribute( 'aria-hidden' );
+
+			if( !wasPresent ) {
+				// Dispatch an event indicating the slide is now visible
+				dispatchEvent({
+					target: slide,
+					type: 'visible',
+					bubbles: false
+				});
+			}
+
+			// If this slide has a state associated with it, add it
+			// onto the current state of the deck
+			let slideState = slide.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;
+
+	}
+
+	/**
+	 * Shows all fragment elements within the given contaienr.
+	 */
+	function showFragmentsIn( container ) {
+
+		Util.queryAll( container, '.fragment' ).forEach( fragment => {
+			fragment.classList.add( 'visible' );
+			fragment.classList.remove( 'current-fragment' );
+		} );
+
+	}
+
+	/**
+	 * Hides all fragment elements within the given contaienr.
+	 */
+	function hideFragmentsIn( container ) {
+
+		Util.queryAll( container, '.fragment.visible' ).forEach( fragment => {
+			fragment.classList.remove( 'visible', 'current-fragment' );
+		} );
+
+	}
+
+	/**
+	 * 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
+		let horizontalSlides = getHorizontalSlides(),
+			horizontalSlidesLength = horizontalSlides.length,
+			distanceX,
+			distanceY;
+
+		if( horizontalSlidesLength && typeof indexh !== 'undefined' ) {
+
+			// The number of steps away from the present slide that will
+			// be visible
+			let viewDistance = overview.isActive() ? 10 : config.viewDistance;
+
+			// Shorten the view distance on devices that typically have
+			// less resources
+			if( Device.isMobile ) {
+				viewDistance = overview.isActive() ? 6 : config.mobileViewDistance;
+			}
+
+			// All slides need to be visible when exporting to PDF
+			if( print.isPrintingPDF() ) {
+				viewDistance = Number.MAX_VALUE;
+			}
+
+			for( let x = 0; x < horizontalSlidesLength; x++ ) {
+				let horizontalSlide = horizontalSlides[x];
+
+				let verticalSlides = Util.queryAll( horizontalSlide, '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 ) {
+					slideContent.load( horizontalSlide );
+				}
+				else {
+					slideContent.unload( horizontalSlide );
+				}
+
+				if( verticalSlidesLength ) {
+
+					let oy = getPreviousVerticalIndex( horizontalSlide );
+
+					for( let y = 0; y < verticalSlidesLength; y++ ) {
+						let verticalSlide = verticalSlides[y];
+
+						distanceY = x === ( indexh || 0 ) ? Math.abs( ( indexv || 0 ) - y ) : Math.abs( y - oy );
+
+						if( distanceX + distanceY < viewDistance ) {
+							slideContent.load( verticalSlide );
+						}
+						else {
+							slideContent.unload( verticalSlide );
+						}
+					}
+
+				}
+			}
+
+			// Flag if there are ANY vertical slides, anywhere in the deck
+			if( hasVerticalSlides() ) {
+				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( hasHorizontalSlides() ) {
+				dom.wrapper.classList.add( 'has-horizontal-slides' );
+			}
+			else {
+				dom.wrapper.classList.remove( 'has-horizontal-slides' );
+			}
+
+		}
+
+	}
+
+	/**
+	 * Determine what available routes there are for navigation.
+	 *
+	 * @return {{left: boolean, right: boolean, up: boolean, down: boolean}}
+	 */
+	function availableRoutes({ includeFragments = false } = {}) {
+
+		let horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
+			verticalSlides = dom.wrapper.querySelectorAll( VERTICAL_SLIDES_SELECTOR );
+
+		let routes = {
+			left: indexh > 0,
+			right: indexh < horizontalSlides.length - 1,
+			up: indexv > 0,
+			down: indexv < verticalSlides.length - 1
+		};
+
+		// Looped presentations can always be navigated as long as
+		// there are slides available
+		if( config.loop ) {
+			if( horizontalSlides.length > 1 ) {
+				routes.left = true;
+				routes.right = true;
+			}
+
+			if( verticalSlides.length > 1 ) {
+				routes.up = true;
+				routes.down = true;
+			}
+		}
+
+		if ( horizontalSlides.length > 1 && config.navigationMode === 'linear' ) {
+			routes.right = routes.right || routes.down;
+			routes.left = routes.left || routes.up;
+		}
+
+		// If includeFragments is set, a route will be considered
+		// available if either a slid OR fragment is available in
+		// the given direction
+		if( includeFragments === true ) {
+			let fragmentRoutes = fragments.availableRoutes();
+			routes.left = routes.left || fragmentRoutes.prev;
+			routes.up = routes.up || fragmentRoutes.prev;
+			routes.down = routes.down || fragmentRoutes.next;
+			routes.right = routes.right || fragmentRoutes.next;
+		}
+
+		// Reverse horizontal controls for rtl
+		if( config.rtl ) {
+			let left = routes.left;
+			routes.left = routes.right;
+			routes.right = left;
+		}
+
+		return routes;
+
+	}
+
+	/**
+	 * Returns the number of past slides. This can be used as a global
+	 * flattened index for slides.
+	 *
+	 * @param {HTMLElement} [slide=currentSlide] The slide we're counting before
+	 *
+	 * @return {number} Past slide count
+	 */
+	function getSlidePastCount( slide = currentSlide ) {
+
+		let horizontalSlides = getHorizontalSlides();
+
+		// The number of past slides
+		let pastCount = 0;
+
+		// Step through all slides and count the past ones
+		mainLoop: for( let i = 0; i < horizontalSlides.length; i++ ) {
+
+			let horizontalSlide = horizontalSlides[i];
+			let verticalSlides = horizontalSlide.querySelectorAll( 'section' );
+
+			for( let j = 0; j < verticalSlides.length; j++ ) {
+
+				// Stop as soon as we arrive at the present
+				if( verticalSlides[j] === slide ) {
+					break mainLoop;
+				}
+
+				// Don't count slides with the "uncounted" class
+				if( verticalSlides[j].dataset.visibility !== 'uncounted' ) {
+					pastCount++;
+				}
+
+			}
+
+			// Stop as soon as we arrive at the present
+			if( horizontalSlide === slide ) {
+				break;
+			}
+
+			// Don't count the wrapping section for vertical slides and
+			// slides marked as uncounted
+			if( horizontalSlide.classList.contains( 'stack' ) === false && horizontalSlide.dataset.visibility !== 'uncounted' ) {
+				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
+		let totalCount = getTotalSlides();
+		let pastCount = getSlidePastCount();
+
+		if( currentSlide ) {
+
+			let allFragments = currentSlide.querySelectorAll( '.fragment' );
+
+			// If there are fragments in the current slide those should be
+			// accounted for in the progress.
+			if( allFragments.length > 0 ) {
+				let 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)
+				let fragmentWeight = 0.9;
+
+				// Add fragment progress to the past slide count
+				pastCount += ( visibleFragments.length / allFragments.length ) * fragmentWeight;
+			}
+
+		}
+
+		return Math.min( pastCount / ( totalCount - 1 ), 1 );
+
+	}
+
+	/**
+	 * 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
+		let h = indexh,
+			v = indexv,
+			f;
+
+		// If a slide is specified, return the indices of that slide
+		if( slide ) {
+			let isVertical = isVerticalSlide( slide );
+			let slideh = isVertical ? slide.parentNode : slide;
+
+			// Select all horizontal slides
+			let horizontalSlides = getHorizontalSlides();
+
+			// 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( Util.queryAll( slide.parentNode, 'section' ).indexOf( slide ), 0 );
+			}
+		}
+
+		if( !slide && currentSlide ) {
+			let hasFragments = currentSlide.querySelectorAll( '.fragment' ).length > 0;
+			if( hasFragments ) {
+				let 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, v, f };
+
+	}
+
+	/**
+	 * Retrieves all slides in this presentation.
+	 */
+	function getSlides() {
+
+		return Util.queryAll( dom.wrapper, SLIDES_SELECTOR + ':not(.stack):not([data-visibility="uncounted"])' );
+
+	}
+
+	/**
+	 * Returns a list of all horizontal slides in the deck. Each
+	 * vertical stack is included as one horizontal slide in the
+	 * resulting array.
+	 */
+	function getHorizontalSlides() {
+
+		return Util.queryAll( dom.wrapper, HORIZONTAL_SLIDES_SELECTOR );
+
+	}
+
+	/**
+	 * Returns all vertical slides that exist within this deck.
+	 */
+	function getVerticalSlides() {
+
+		return Util.queryAll( dom.wrapper, '.slides>section>section' );
+
+	}
+
+	/**
+	 * Returns all vertical stacks (each stack can contain multiple slides).
+	 */
+	function getVerticalStacks() {
+
+		return Util.queryAll( dom.wrapper, HORIZONTAL_SLIDES_SELECTOR + '.stack');
+
+	}
+
+	/**
+	 * Returns true if there are at least two horizontal slides.
+	 */
+	function hasHorizontalSlides() {
+
+		return getHorizontalSlides().length > 1;
+	}
+
+	/**
+	 * Returns true if there are at least two vertical slides.
+	 */
+	function hasVerticalSlides() {
+
+		return getVerticalSlides().length > 1;
+
+	}
+
+	/**
+	 * Returns an array of objects where each object represents the
+	 * attributes on its respective slide.
+	 */
+	function getSlidesAttributes() {
+
+		return getSlides().map( slide => {
+
+			let attributes = {};
+			for( let i = 0; i < slide.attributes.length; i++ ) {
+				let attribute = slide.attributes[ i ];
+				attributes[ attribute.name ] = attribute.value;
+			}
+			return attributes;
+
+		} );
+
+	}
+
+	/**
+	 * Retrieves the total number of slides in this presentation.
+	 *
+	 * @return {number}
+	 */
+	function getTotalSlides() {
+
+		return getSlides().length;
+
+	}
+
+	/**
+	 * Returns the slide element matching the specified index.
+	 *
+	 * @return {HTMLElement}
+	 */
+	function getSlide( x, y ) {
+
+		let horizontalSlide = getHorizontalSlides()[ x ];
+		let verticalSlides = horizontalSlide && horizontalSlide.querySelectorAll( 'section' );
+
+		if( verticalSlides && verticalSlides.length && typeof y === 'number' ) {
+			return verticalSlides ? verticalSlides[ y ] : undefined;
+		}
+
+		return horizontalSlide;
+
+	}
+
+	/**
+	 * Returns the background element for the given slide.
+	 * All slides, even the ones with no background properties
+	 * defined, have a background element so as long as the
+	 * index is valid an element will be returned.
+	 *
+	 * @param {mixed} x Horizontal background index OR a slide
+	 * HTML element
+	 * @param {number} y Vertical background index
+	 * @return {(HTMLElement[]|*)}
+	 */
+	function getSlideBackground( x, y ) {
+
+		let slide = typeof x === 'number' ? getSlide( x, y ) : x;
+		if( slide ) {
+			return slide.slideBackgroundElement;
+		}
+
+		return undefined;
+
+	}
+
+	/**
+	 * 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() {
+
+		let indices = getIndices();
+
+		return {
+			indexh: indices.h,
+			indexv: indices.v,
+			indexf: indices.f,
+			paused: isPaused(),
+			overview: overview.isActive()
+		};
+
+	}
+
+	/**
+	 * 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( Util.deserialize( state.indexh ), Util.deserialize( state.indexv ), Util.deserialize( state.indexf ) );
+
+			let pausedFlag = Util.deserialize( state.paused ),
+				overviewFlag = Util.deserialize( state.overview );
+
+			if( typeof pausedFlag === 'boolean' && pausedFlag !== isPaused() ) {
+				togglePause( pausedFlag );
+			}
+
+			if( typeof overviewFlag === 'boolean' && overviewFlag !== overview.isActive() ) {
+				overview.toggle( overviewFlag );
+			}
+		}
+
+	}
+
+	/**
+	 * Cues a new automated slide if enabled in the config.
+	 */
+	function cueAutoSlide() {
+
+		cancelAutoSlide();
+
+		if( currentSlide && config.autoSlide !== false ) {
+
+			let fragment = currentSlide.querySelector( '.current-fragment[data-autoslide]' );
+
+			let fragmentAutoSlide = fragment ? fragment.getAttribute( 'data-autoslide' ) : null;
+			let parentAutoSlide = currentSlide.parentNode ? currentSlide.parentNode.getAttribute( 'data-autoslide' ) : null;
+			let 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 ) {
+					Util.queryAll( currentSlide, 'video, audio' ).forEach( 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() && !overview.isActive() && ( !isLastSlide() || fragments.availableRoutes().next || config.loop === true ) ) {
+				autoSlideTimeout = setTimeout( () => {
+					if( typeof config.autoSlideMethod === 'function' ) {
+						config.autoSlideMethod()
+					}
+					else {
+						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({ type: 'autoslidepaused' });
+			clearTimeout( autoSlideTimeout );
+
+			if( autoSlidePlayer ) {
+				autoSlidePlayer.setPlaying( false );
+			}
+		}
+
+	}
+
+	function resumeAutoSlide() {
+
+		if( autoSlide && autoSlidePaused ) {
+			autoSlidePaused = false;
+			dispatchEvent({ type: 'autoslideresumed' });
+			cueAutoSlide();
+		}
+
+	}
+
+	function navigateLeft({skipFragments=false}={}) {
+
+		navigationHistory.hasNavigatedHorizontally = true;
+
+		// Reverse for RTL
+		if( config.rtl ) {
+			if( ( overview.isActive() || skipFragments || fragments.next() === false ) && availableRoutes().left ) {
+				slide( indexh + 1, config.navigationMode === 'grid' ? indexv : undefined );
+			}
+		}
+		// Normal navigation
+		else if( ( overview.isActive() || skipFragments || fragments.prev() === false ) && availableRoutes().left ) {
+			slide( indexh - 1, config.navigationMode === 'grid' ? indexv : undefined );
+		}
+
+	}
+
+	function navigateRight({skipFragments=false}={}) {
+
+		navigationHistory.hasNavigatedHorizontally = true;
+
+		// Reverse for RTL
+		if( config.rtl ) {
+			if( ( overview.isActive() || skipFragments || fragments.prev() === false ) && availableRoutes().right ) {
+				slide( indexh - 1, config.navigationMode === 'grid' ? indexv : undefined );
+			}
+		}
+		// Normal navigation
+		else if( ( overview.isActive() || skipFragments || fragments.next() === false ) && availableRoutes().right ) {
+			slide( indexh + 1, config.navigationMode === 'grid' ? indexv : undefined );
+		}
+
+	}
+
+	function navigateUp({skipFragments=false}={}) {
+
+		// Prioritize hiding fragments
+		if( ( overview.isActive() || skipFragments || fragments.prev() === false ) && availableRoutes().up ) {
+			slide( indexh, indexv - 1 );
+		}
+
+	}
+
+	function navigateDown({skipFragments=false}={}) {
+
+		navigationHistory.hasNavigatedVertically = true;
+
+		// Prioritize revealing fragments
+		if( ( overview.isActive() || skipFragments || fragments.next() === 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({skipFragments=false}={}) {
+
+		// Prioritize revealing fragments
+		if( skipFragments || fragments.prev() === false ) {
+			if( availableRoutes().up ) {
+				navigateUp({skipFragments});
+			}
+			else {
+				// Fetch the previous horizontal slide, if there is one
+				let previousSlide;
+
+				if( config.rtl ) {
+					previousSlide = Util.queryAll( dom.wrapper, HORIZONTAL_SLIDES_SELECTOR + '.future' ).pop();
+				}
+				else {
+					previousSlide = Util.queryAll( dom.wrapper, HORIZONTAL_SLIDES_SELECTOR + '.past' ).pop();
+				}
+
+				// When going backwards and arriving on a stack we start
+				// at the bottom of the stack
+				if( previousSlide && previousSlide.classList.contains( 'stack' ) ) {
+					let v = ( previousSlide.querySelectorAll( 'section' ).length - 1 ) || undefined;
+					let h = indexh - 1;
+					slide( h, v );
+				}
+				else {
+					navigateLeft({skipFragments});
+				}
+			}
+		}
+
+	}
+
+	/**
+	 * The reverse of #navigatePrev().
+	 */
+	function navigateNext({skipFragments=false}={}) {
+
+		navigationHistory.hasNavigatedHorizontally = true;
+		navigationHistory.hasNavigatedVertically = true;
+
+		// Prioritize revealing fragments
+		if( skipFragments || fragments.next() === false ) {
+
+			let routes = availableRoutes();
+
+			// When looping is enabled `routes.down` is always available
+			// so we need a separate check for when we've reached the
+			// end of a stack and should move horizontally
+			if( routes.down && routes.right && config.loop && isLastVerticalSlide() ) {
+				routes.down = false;
+			}
+
+			if( routes.down ) {
+				navigateDown({skipFragments});
+			}
+			else if( config.rtl ) {
+				navigateLeft({skipFragments});
+			}
+			else {
+				navigateRight({skipFragments});
+			}
+		}
+
+	}
+
+
+	// --------------------------------------------------------------------//
+	// ----------------------------- EVENTS -------------------------------//
+	// --------------------------------------------------------------------//
+
+	/**
+	 * Called by all event handlers that are based on user
+	 * input.
+	 *
+	 * @param {object} [event]
+	 */
+	function onUserInput( event ) {
+
+		if( config.autoSlideStoppable ) {
+			pauseAutoSlide();
+		}
+
+	}
+
+	/**
+	* Listener for post message events posted to this window.
+	*/
+	function onPostMessage( event ) {
+
+		let 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' ) {
+
+				if( POST_MESSAGE_METHOD_BLACKLIST.test( data.method ) === false ) {
+
+					const result = Reveal[data.method].apply( Reveal, data.args );
+
+					// Dispatch a postMessage event with the returned value from
+					// our method invocation for getter functions
+					dispatchPostMessage( 'callback', { method: data.method, result: result } );
+
+				}
+				else {
+					console.warn( 'reveal.js: "'+ data.method +'" is is blacklisted from the postMessage API' );
+				}
+
+			}
+		}
+
+	}
+
+	/**
+	 * Event listener for transition end on the current slide.
+	 *
+	 * @param {object} [event]
+	 */
+	function onTransitionEnd( event ) {
+
+		if( transition === 'running' && /section/gi.test( event.target.nodeName ) ) {
+			transition = 'idle';
+			dispatchEvent({
+				type: 'slidetransitionend',
+				data: { indexh, indexv, previousSlide, currentSlide }
+			});
+		}
+
+	}
+
+	/**
+	 * A global listener for all click events inside of the
+	 * .slides container.
+	 *
+	 * @param {object} [event]
+	 */
+	function onSlidesClicked( event ) {
+
+		const anchor = Util.closest( event.target, 'a[href^="#"]' );
+
+		// If a hash link is clicked, we find the target slide
+		// and navigate to it. We previously relied on 'hashchange'
+		// for links like these but that prevented media with
+		// audio tracks from playing in mobile browsers since it
+		// wasn't considered a direct interaction with the document.
+		if( anchor ) {
+			const hash = anchor.getAttribute( 'href' );
+			const indices = location.getIndicesFromHash( hash );
+
+			if( indices ) {
+				Reveal.slide( indices.h, indices.v, indices.f );
+				event.preventDefault();
+			}
+		}
+
+	}
+
+	/**
+	 * 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 ) {
+
+		// If, after clicking a link or similar and we're coming back,
+		// focus the document.body to ensure we can use keyboard shortcuts
+		if( document.hidden === 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();
+		}
+
+	}
+
+	/**
+	 * Handler for the document level 'fullscreenchange' event.
+	 *
+	 * @param {object} [event]
+	 */
+	function onFullscreenChange( event ) {
+
+		let element = document.fullscreenElement || document.webkitFullscreenElement;
+		if( element === dom.wrapper ) {
+			event.stopImmediatePropagation();
+
+			// Timeout to avoid layout shift in Safari
+			setTimeout( () => {
+				Reveal.layout();
+				Reveal.focus.focus(); // focus.focus :'(
+			}, 1 );
+		}
+
+	}
+
+	/**
+	 * 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' ) ) {
+			let 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( isLastSlide() && config.loop === false ) {
+			slide( 0, 0 );
+			resumeAutoSlide();
+		}
+		// Resume
+		else if( autoSlidePaused ) {
+			resumeAutoSlide();
+		}
+		// Pause
+		else {
+			pauseAutoSlide();
+		}
+
+	}
+
+
+	// --------------------------------------------------------------------//
+	// ------------------------------- API --------------------------------//
+	// --------------------------------------------------------------------//
+
+	// The public reveal.js API
+	const API = {
+		VERSION,
+
+		initialize,
+		configure,
+		destroy,
+
+		sync,
+		syncSlide,
+		syncFragments: fragments.sync.bind( fragments ),
+
+		// Navigation methods
+		slide,
+		left: navigateLeft,
+		right: navigateRight,
+		up: navigateUp,
+		down: navigateDown,
+		prev: navigatePrev,
+		next: navigateNext,
+
+		// Navigation aliases
+		navigateLeft, navigateRight, navigateUp, navigateDown, navigatePrev, navigateNext,
+
+		// Fragment methods
+		navigateFragment: fragments.goto.bind( fragments ),
+		prevFragment: fragments.prev.bind( fragments ),
+		nextFragment: fragments.next.bind( fragments ),
+
+		// Event binding
+		on,
+		off,
+
+		// Legacy event binding methods left in for backwards compatibility
+		addEventListener: on,
+		removeEventListener: off,
+
+		// Forces an update in slide layout
+		layout,
+
+		// Randomizes the order of slides
+		shuffle,
+
+		// Returns an object with the available routes as booleans (left/right/top/bottom)
+		availableRoutes,
+
+		// Returns an object with the available fragments as booleans (prev/next)
+		availableFragments: fragments.availableRoutes.bind( fragments ),
+
+		// Toggles a help overlay with keyboard shortcuts
+		toggleHelp,
+
+		// Toggles the overview mode on/off
+		toggleOverview: overview.toggle.bind( overview ),
+
+		// Toggles the "black screen" mode on/off
+		togglePause,
+
+		// Toggles the auto slide mode on/off
+		toggleAutoSlide,
+
+		// Toggles visibility of the jump-to-slide UI
+		toggleJumpToSlide,
+
+		// Slide navigation checks
+		isFirstSlide,
+		isLastSlide,
+		isLastVerticalSlide,
+		isVerticalSlide,
+
+		// State checks
+		isPaused,
+		isAutoSliding,
+		isSpeakerNotes: notes.isSpeakerNotesWindow.bind( notes ),
+		isOverview: overview.isActive.bind( overview ),
+		isFocused: focus.isFocused.bind( focus ),
+		isPrintingPDF: print.isPrintingPDF.bind( print ),
+
+		// Checks if reveal.js has been loaded and is ready for use
+		isReady: () => ready,
+
+		// Slide preloading
+		loadSlide: slideContent.load.bind( slideContent ),
+		unloadSlide: slideContent.unload.bind( slideContent ),
+
+		// Media playback
+		startEmbeddedContent: () => slideContent.startEmbeddedContent( currentSlide ),
+		stopEmbeddedContent: () => slideContent.stopEmbeddedContent( currentSlide, { unloadIframes: false } ),
+
+		// Preview management
+		showPreview,
+		hidePreview: closeOverlay,
+
+		// Adds or removes all internal event listeners
+		addEventListeners,
+		removeEventListeners,
+		dispatchEvent,
+
+		// Facility for persisting and restoring the presentation state
+		getState,
+		setState,
+
+		// Presentation progress on range of 0-1
+		getProgress,
+
+		// Returns the indices of the current, or specified, slide
+		getIndices,
+
+		// Returns an Array of key:value maps of the attributes of each
+		// slide in the deck
+		getSlidesAttributes,
+
+		// Returns the number of slides that we have passed
+		getSlidePastCount,
+
+		// Returns the total number of slides
+		getTotalSlides,
+
+		// Returns the slide element at the specified index
+		getSlide,
+
+		// Returns the previous slide element, may be null
+		getPreviousSlide: () => previousSlide,
+
+		// Returns the current slide element
+		getCurrentSlide: () => currentSlide,
+
+		// Returns the slide background element at the specified index
+		getSlideBackground,
+
+		// Returns the speaker notes string for a slide, or null
+		getSlideNotes: notes.getSlideNotes.bind( notes ),
+
+		// Returns an Array of all slides
+		getSlides,
+
+		// Returns an array with all horizontal/vertical slides in the deck
+		getHorizontalSlides,
+		getVerticalSlides,
+
+		// Checks if the presentation contains two or more horizontal
+		// and vertical slides
+		hasHorizontalSlides,
+		hasVerticalSlides,
+
+		// Checks if the deck has navigated on either axis at least once
+		hasNavigatedHorizontally: () => navigationHistory.hasNavigatedHorizontally,
+		hasNavigatedVertically: () => navigationHistory.hasNavigatedVertically,
+
+		// Adds/removes a custom key binding
+		addKeyBinding: keyboard.addKeyBinding.bind( keyboard ),
+		removeKeyBinding: keyboard.removeKeyBinding.bind( keyboard ),
+
+		// Programmatically triggers a keyboard event
+		triggerKey: keyboard.triggerKey.bind( keyboard ),
+
+		// Registers a new shortcut to include in the help overlay
+		registerKeyboardShortcut: keyboard.registerKeyboardShortcut.bind( keyboard ),
+
+		getComputedSlideSize,
+
+		// Returns the current scale of the presentation content
+		getScale: () => scale,
+
+		// Returns the current configuration object
+		getConfig: () => config,
+
+		// Helper method, retrieves query string as a key:value map
+		getQueryHash: Util.getQueryHash,
+
+		// Returns the path to the current slide as represented in the URL
+		getSlidePath: location.getHash.bind( location ),
+
+		// Returns reveal.js DOM elements
+		getRevealElement: () => revealElement,
+		getSlidesElement: () => dom.slides,
+		getViewportElement: () => dom.viewport,
+		getBackgroundsElement: () => backgrounds.element,
+
+		// API for registering and retrieving plugins
+		registerPlugin: plugins.registerPlugin.bind( plugins ),
+		hasPlugin: plugins.hasPlugin.bind( plugins ),
+		getPlugin: plugins.getPlugin.bind( plugins ),
+		getPlugins: plugins.getRegisteredPlugins.bind( plugins )
+
+	};
+
+	// Our internal API which controllers have access to
+	Util.extend( Reveal, {
+		...API,
+
+		// Methods for announcing content to screen readers
+		announceStatus,
+		getStatusText,
+
+		// Controllers
+		print,
+		focus,
+		progress,
+		controls,
+		location,
+		overview,
+		fragments,
+		slideContent,
+		slideNumber,
+
+		onUserInput,
+		closeOverlay,
+		updateSlidesVisibility,
+		layoutSlideContents,
+		transformSlides,
+		cueAutoSlide,
+		cancelAutoSlide
+	} );
+
+	return API;
+
+};