text: import SlideContent from './controllers/slidecontent.js'
  import SlideNumber from './controllers/slidenumber.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'
  
  /**
   * reveal.js
   * https://revealjs.com
   * MIT licensed
   *
   * Copyright (C) 2020 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 = {};
  
  	// The reveal.js version
  	const VERSION = '4.0.0-rc.1';
  
  	// 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 ),
  		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 ) {
  
  		// Cache references to key DOM elements
  		dom.wrapper = revealElement;
  		dom.slides = revealElement.querySelector( '.slides' );
  
  		// Compose our config object
  		config = { ...defaultConfig, ...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 = revealElement.closest( '.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;
  
  		// 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
  		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();
  				} );
  			}
  		}
  
  	}
  
  	/**
  	 * 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();
  		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 );
  
  	}
  
  	/**
  	 * 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', 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' );
  						}
  
  					}
  				}
  			}, 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 );
  
  		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( '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( 'transitionend', onTransitionEnd, false );
  		dom.pauseOverlay.removeEventListener( 'click', resume, false );
  
  	}
  
  	/**
  	 * 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 );
  		}
  
  	}
  
  	/**
  	 * 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 {
  					// Zoom Scaling
  					// Content remains crisp no matter how much we scale. Side
  					// effects are minor differences in text layout and iframe
  					// viewports changing size. A 200x200 iframe viewport in a
  					// 2x zoomed presentation ends up having a 400x400 viewport.
  					if( scale > 1 && Device.supportsZoom && window.devicePixelRatio < 2 ) {
  						dom.slides.style.zoom = scale;
  						dom.slides.style.left = '';
  						dom.slides.style.top = '';
  						dom.slides.style.bottom = '';
  						dom.slides.style.right = '';
  						transformSlides( { layout: '' } );
  					}
  					// Transform Scaling
  					// Content layout remains the exact same when scaled up.
  					// Side effect is content becoming blurred, especially with
  					// high scale values on ldpi screens.
  					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
  						}
  					});
  				}
  			}
  
  			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 ) {
  
  		const 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
  			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 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
  		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' ) ) {
  				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: o
  				}
  			});
  		}
  
  		// Handle embedded content
  		if( slideChanged || !previousSlide ) {
  			slideContent.stopEmbeddedContent( previousSlide );
  			slideContent.startEmbeddedContent( currentSlide );
  		}
  
  		// Announce the current slide contents to screen readers
  		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();
  
  		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() {
  
  		getHorizontalSlides().forEach( ( slide, i, slides ) => {
  
  			// 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
  		let slides = Util.queryAll( dom.wrapper, selector ),
  			slidesLength = slides.length;
  
  		let printMode = print.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( let i = 0; i < slidesLength; i++ ) {
  				let element = slides[i];
  
  				let reverse = config.rtl && !isVerticalSlide( element );
  
  				element.classList.remove( 'past', 'present', '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
  						Util.queryAll( element, '.fragment' ).forEach( fragment => {
  							fragment.classList.add( 'visible' );
  							fragment.classList.remove( 'current-fragment' );
  						} );
  					}
  				}
  				else if( i > index ) {
  					// Any element subsequent to index is given the 'future' class
  					element.classList.add( reverse ? 'past' : 'future' );
  
  					if( config.fragments ) {
  						// Hide all fragments in future slides
  						Util.queryAll( element, '.fragment.visible' ).forEach( fragment => {
  							fragment.classList.remove( 'visible', 'current-fragment' );
  						} );
  					}
  				}
  			}
  
  			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;
  
  	}
  
  	/**
  	 * 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
  		// availalbe 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' );
  
  			// 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' );
  
  			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() {
  
  		navigationHistory.hasNavigatedHorizontally = true;
  
  		// Reverse for RTL
  		if( config.rtl ) {
  			if( ( overview.isActive() || fragments.next() === false ) && availableRoutes().left ) {
  				slide( indexh + 1, config.navigationMode === 'grid' ? indexv : undefined );
  			}
  		}
  		// Normal navigation
  		else if( ( overview.isActive() || fragments.prev() === false ) && availableRoutes().left ) {
  			slide( indexh - 1, config.navigationMode === 'grid' ? indexv : undefined );
  		}
  
  	}
  
  	function navigateRight() {
  
  		navigationHistory.hasNavigatedHorizontally = true;
  
  		// Reverse for RTL
  		if( config.rtl ) {
  			if( ( overview.isActive() || fragments.prev() === false ) && availableRoutes().right ) {
  				slide( indexh - 1, config.navigationMode === 'grid' ? indexv : undefined );
  			}
  		}
  		// Normal navigation
  		else if( ( overview.isActive() || fragments.next() === false ) && availableRoutes().right ) {
  			slide( indexh + 1, config.navigationMode === 'grid' ? indexv : undefined );
  		}
  
  	}
  
  	function navigateUp() {
  
  		// Prioritize hiding fragments
  		if( ( overview.isActive() || fragments.prev() === false ) && availableRoutes().up ) {
  			slide( indexh, indexv - 1 );
  		}
  
  	}
  
  	function navigateDown() {
  
  		navigationHistory.hasNavigatedVertically = true;
  
  		// Prioritize revealing fragments
  		if( ( overview.isActive() || 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() {
  
  		// Prioritize revealing fragments
  		if( fragments.prev() === false ) {
  			if( availableRoutes().up ) {
  				navigateUp();
  			}
  			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();
  				}
  
  				if( previousSlide ) {
  					let v = ( previousSlide.querySelectorAll( 'section' ).length - 1 ) || undefined;
  					let h = indexh - 1;
  					slide( h, v );
  				}
  			}
  		}
  
  	}
  
  	/**
  	 * The reverse of #navigatePrev().
  	 */
  	function navigateNext() {
  
  		navigationHistory.hasNavigatedHorizontally = true;
  		navigationHistory.hasNavigatedVertically = true;
  
  		// Prioritize revealing fragments
  		if( 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( currentSlide ) ) {
  				routes.down = false;
  			}
  
  			if( routes.down ) {
  				navigateDown();
  			}
  			else if( config.rtl ) {
  				navigateLeft();
  			}
  			else {
  				navigateRight();
  			}
  		}
  
  	}
  
  
  	// --------------------------------------------------------------------//
  	// ----------------------------- EVENTS -------------------------------//
  	// --------------------------------------------------------------------//
  
  	/**
  	 * Called by all event handlers that are based on user
  	 * input.
  	 *
  	 * @param {object} [event]
  	 */
  	function onUserInput( event ) {
  
  		if( config.autoSlideStoppable ) {
  			pauseAutoSlide();
  		}
  
  	}
  
  	/**
  	 * 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 }
  			});
  		}
  
  	}
  
  	/**
  	 * 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();
  		}
  
  	}
  
  	/**
  	 * 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,
  
  		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,
  
  		// 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 ),
  
  		// 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 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;
  
  };
  