text: /*!
   * reveal.js
   * http://lab.hakim.se/reveal-js
   * MIT licensed
   *
   * Copyright (C) 2014 Hakim El Hattab, http://hakim.se
   */
  var Reveal = (function(){
  
  	'use strict';
  
  	var SLIDES_SELECTOR = '.reveal .slides section',
  		HORIZONTAL_SLIDES_SELECTOR = '.reveal .slides>section',
  		VERTICAL_SLIDES_SELECTOR = '.reveal .slides>section.present>section',
  		HOME_SLIDE_SELECTOR = '.reveal .slides>section:first-of-type',
  
  		// Configurations defaults, can be overridden at initialization time
  		config = {
  
  			// The "normal" size of the presentation, aspect ratio will be preserved
  			// when the presentation is scaled to fit different resolutions
  			width: 960,
  			height: 700,
  
  			// Factor of the display size that should remain empty around the content
  			margin: 0.1,
  
  			// Bounds for smallest/largest possible scale to apply to content
  			minScale: 0.2,
  			maxScale: 1.0,
  
  			// Display controls in the bottom right corner
  			controls: true,
  
  			// Display a presentation progress bar
  			progress: true,
  
  			// Display the page number of the current slide
  			slideNumber: false,
  
  			// Push each slide change to the browser history
  			history: false,
  
  			// Enable keyboard shortcuts for navigation
  			keyboard: true,
  
  			// Enable the slide overview mode
  			overview: true,
  
  			// Vertical centering of slides
  			center: true,
  
  			// Enables touch navigation on devices with touch input
  			touch: true,
  
  			// Loop the presentation
  			loop: false,
  
  			// Change the presentation direction to be RTL
  			rtl: false,
  
  			// Turns fragments on and off globally
  			fragments: true,
  
  			// Flags if the presentation is running in an embedded mode,
  			// i.e. contained within a limited portion of the screen
  			embedded: false,
  
  			// Number of milliseconds between automatically proceeding to the
  			// next slide, disabled when set to 0, this value can be overwritten
  			// by using a data-autoslide attribute on your slides
  			autoSlide: 0,
  
  			// Stop auto-sliding after user input
  			autoSlideStoppable: true,
  
  			// Enable slide navigation via mouse wheel
  			mouseWheel: false,
  
  			// Apply a 3D roll to links on hover
  			rollingLinks: false,
  
  			// Hides the address bar on mobile devices
  			hideAddressBar: true,
  
  			// Opens links in an iframe preview overlay
  			previewLinks: false,
  
  			// Focuses body when page changes visiblity to ensure keyboard shortcuts work
  			focusBodyOnPageVisiblityChange: true,
  
  			// Theme (see /css/theme)
  			theme: null,
  
  			// Transition style
  			transition: 'default', // default/cube/page/concave/zoom/linear/fade/none
  
  			// Transition speed
  			transitionSpeed: 'default', // default/fast/slow
  
  			// Transition style for full page slide backgrounds
  			backgroundTransition: 'default', // default/linear/none
  
  			// Parallax background image
  			parallaxBackgroundImage: '', // CSS syntax, e.g. "a.jpg"
  
  			// Parallax background size
  			parallaxBackgroundSize: '', // CSS syntax, e.g. "3000px 2000px"
  
  			// Number of slides away from the current that are visible
  			viewDistance: 3,
  
  			// Script dependencies to load
  			dependencies: []
  
  		},
  
  		// Flags if reveal.js is loaded (has dispatched the 'ready' event)
  		loaded = false,
  
  		// The horizontal and vertical index of the currently active slide
  		indexh,
  		indexv,
  
  		// The previous and current slide HTML elements
  		previousSlide,
  		currentSlide,
  
  		previousBackground,
  
  		// Slides may hold a data-state attribute which we pick up and apply
  		// as a class to the body. This list contains the combined state of
  		// all current slides.
  		state = [],
  
  		// The current scale of the presentation (see width/height config)
  		scale = 1,
  
  		// Cached references to DOM elements
  		dom = {},
  
  		// Features supported by the browser, see #checkCapabilities()
  		features = {},
  
  		// Client is a mobile device, see #checkCapabilities()
  		isMobileDevice,
  
  		// Throttles mouse wheel navigation
  		lastMouseWheelStep = 0,
  
  		// Delays updates to the URL due to a Chrome thumbnailer bug
  		writeURLTimeout = 0,
  
  		// A delay used to activate the overview mode
  		activateOverviewTimeout = 0,
  
  		// A delay used to deactivate the overview mode
  		deactivateOverviewTimeout = 0,
  
  		// Flags if the interaction event listeners are bound
  		eventsAreBound = false,
  
  		// The current auto-slide duration
  		autoSlide = 0,
  
  		// Auto slide properties
  		autoSlidePlayer,
  		autoSlideTimeout = 0,
  		autoSlideStartTime = -1,
  		autoSlidePaused = false,
  
  		// Holds information about the currently ongoing touch input
  		touch = {
  			startX: 0,
  			startY: 0,
  			startSpan: 0,
  			startCount: 0,
  			captured: false,
  			threshold: 40
  		};
  
  	/**
  	 * Starts up the presentation if the client is capable.
  	 */
  	function initialize( options ) {
  
  		checkCapabilities();
  
  		if( !features.transforms2d && !features.transforms3d ) {
  			document.body.setAttribute( 'class', 'no-transforms' );
  
  			// If the browser doesn't support core features we won't be
  			// using JavaScript to control the presentation
  			return;
  		}
  
  		// Force a layout when the whole page, incl fonts, has loaded
  		window.addEventListener( 'load', layout, false );
  
  		var query = Reveal.getQueryHash();
  
  		// Do not accept new dependencies via query config to avoid
  		// the potential of malicious script injection
  		if( typeof query['dependencies'] !== 'undefined' ) delete query['dependencies'];
  
  		// Copy options over to our config object
  		extend( config, options );
  		extend( config, query );
  
  		// Hide the address bar in mobile browsers
  		hideAddressBar();
  
  		// Loads the dependencies and continues to #start() once done
  		load();
  
  	}
  
  	/**
  	 * Inspect the client to see what it's capable of, this
  	 * should only happens once per runtime.
  	 */
  	function checkCapabilities() {
  
  		features.transforms3d = 'WebkitPerspective' in document.body.style ||
  								'MozPerspective' in document.body.style ||
  								'msPerspective' in document.body.style ||
  								'OPerspective' in document.body.style ||
  								'perspective' in document.body.style;
  
  		features.transforms2d = 'WebkitTransform' in document.body.style ||
  								'MozTransform' in document.body.style ||
  								'msTransform' in document.body.style ||
  								'OTransform' in document.body.style ||
  								'transform' in document.body.style;
  
  		features.requestAnimationFrameMethod = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame;
  		features.requestAnimationFrame = typeof features.requestAnimationFrameMethod === 'function';
  
  		features.canvas = !!document.createElement( 'canvas' ).getContext;
  
  		isMobileDevice = navigator.userAgent.match( /(iphone|ipod|android)/gi );
  
  	}
  
  
      /**
       * Loads the dependencies of reveal.js. Dependencies are
       * defined via the configuration option 'dependencies'
       * and will be loaded prior to starting/binding reveal.js.
       * Some dependencies may have an 'async' flag, if so they
       * will load after reveal.js has been started up.
       */
  	function load() {
  
  		var scripts = [],
  			scriptsAsync = [],
  			scriptsToPreload = 0;
  
  		// Called once synchronous scripts finish loading
  		function proceed() {
  			if( scriptsAsync.length ) {
  				// Load asynchronous scripts
  				head.js.apply( null, scriptsAsync );
  			}
  
  			start();
  		}
  
  		function loadScript( s ) {
  			head.ready( s.src.match( /([\w\d_\-]*)\.?js$|[^\\\/]*$/i )[0], function() {
  				// Extension may contain callback functions
  				if( typeof s.callback === 'function' ) {
  					s.callback.apply( this );
  				}
  
  				if( --scriptsToPreload === 0 ) {
  					proceed();
  				}
  			});
  		}
  
  		for( var i = 0, len = config.dependencies.length; i < len; i++ ) {
  			var s = config.dependencies[i];
  
  			// Load if there's no condition or the condition is truthy
  			if( !s.condition || s.condition() ) {
  				if( s.async ) {
  					scriptsAsync.push( s.src );
  				}
  				else {
  					scripts.push( s.src );
  				}
  
  				loadScript( s );
  			}
  		}
  
  		if( scripts.length ) {
  			scriptsToPreload = scripts.length;
  
  			// Load synchronous scripts
  			head.js.apply( null, scripts );
  		}
  		else {
  			proceed();
  		}
  
  	}
  
  	/**
  	 * Starts up reveal.js by binding input events and navigating
  	 * to the current URL deeplink if there is one.
  	 */
  	function start() {
  
  		// Make sure we've got all the DOM elements we need
  		setupDOM();
  
  		// Resets all vertical slides so that only the first is visible
  		resetVerticalSlides();
  
  		// Updates the presentation to match the current configuration values
  		configure();
  
  		// Read the initial hash
  		readURL();
  
  		// Update all backgrounds
  		updateBackground( true );
  
  		// Notify listeners that the presentation is ready but use a 1ms
  		// timeout to ensure it's not fired synchronously after #initialize()
  		setTimeout( function() {
  			// Enable transitions now that we're loaded
  			dom.slides.classList.remove( 'no-transition' );
  
  			loaded = true;
  
  			dispatchEvent( 'ready', {
  				'indexh': indexh,
  				'indexv': indexv,
  				'currentSlide': currentSlide
  			} );
  		}, 1 );
  
  	}
  
  	/**
  	 * 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() {
  
  		// Cache references to key DOM elements
  		dom.theme = document.querySelector( '#theme' );
  		dom.wrapper = document.querySelector( '.reveal' );
  		dom.slides = document.querySelector( '.reveal .slides' );
  
  		// Prevent transitions while we're loading
  		dom.slides.classList.add( 'no-transition' );
  
  		// Background element
  		dom.background = createSingletonNode( dom.wrapper, 'div', 'backgrounds', null );
  
  		// Progress bar
  		dom.progress = createSingletonNode( dom.wrapper, 'div', 'progress', '<span></span>' );
  		dom.progressbar = dom.progress.querySelector( 'span' );
  
  		// Arrow controls
  		createSingletonNode( dom.wrapper, 'aside', 'controls',
  			'<div class="navigate-left"></div>' +
  			'<div class="navigate-right"></div>' +
  			'<div class="navigate-up"></div>' +
  			'<div class="navigate-down"></div>' );
  
  		// Slide number
  		dom.slideNumber = createSingletonNode( dom.wrapper, 'div', 'slide-number', '' );
  
  		// State background element [DEPRECATED]
  		createSingletonNode( dom.wrapper, 'div', 'state-background', null );
  
  		// Overlay graphic which is displayed during the paused mode
  		createSingletonNode( dom.wrapper, 'div', 'pause-overlay', null );
  
  		// Cache references to elements
  		dom.controls = document.querySelector( '.reveal .controls' );
  
  		// There can be multiple instances of controls throughout the page
  		dom.controlsLeft = toArray( document.querySelectorAll( '.navigate-left' ) );
  		dom.controlsRight = toArray( document.querySelectorAll( '.navigate-right' ) );
  		dom.controlsUp = toArray( document.querySelectorAll( '.navigate-up' ) );
  		dom.controlsDown = toArray( document.querySelectorAll( '.navigate-down' ) );
  		dom.controlsPrev = toArray( document.querySelectorAll( '.navigate-prev' ) );
  		dom.controlsNext = toArray( document.querySelectorAll( '.navigate-next' ) );
  
  	}
  
  	/**
  	 * Creates an HTML element and returns a reference to it.
  	 * If the element already exists the existing instance will
  	 * be returned.
  	 */
  	function createSingletonNode( container, tagname, classname, innerHTML ) {
  
  		var node = container.querySelector( '.' + classname );
  		if( !node ) {
  			node = document.createElement( tagname );
  			node.classList.add( classname );
  			if( innerHTML !== null ) {
  				node.innerHTML = innerHTML;
  			}
  			container.appendChild( node );
  		}
  		return node;
  
  	}
  
  	/**
  	 * Creates the slide background elements and appends them
  	 * to the background container. One element is created per
  	 * slide no matter if the given slide has visible background.
  	 */
  	function createBackgrounds() {
  
  		if( isPrintingPDF() ) {
  			document.body.classList.add( 'print-pdf' );
  		}
  
  		// Clear prior backgrounds
  		dom.background.innerHTML = '';
  		dom.background.classList.add( 'no-transition' );
  
  		// Helper method for creating a background element for the
  		// given slide
  		function _createBackground( slide, container ) {
  
  			var data = {
  				background: slide.getAttribute( 'data-background' ),
  				backgroundSize: slide.getAttribute( 'data-background-size' ),
  				backgroundImage: slide.getAttribute( 'data-background-image' ),
  				backgroundColor: slide.getAttribute( 'data-background-color' ),
  				backgroundRepeat: slide.getAttribute( 'data-background-repeat' ),
  				backgroundPosition: slide.getAttribute( 'data-background-position' ),
  				backgroundTransition: slide.getAttribute( 'data-background-transition' )
  			};
  
  			var element = document.createElement( 'div' );
  			element.className = 'slide-background';
  
  			if( data.background ) {
  				// Auto-wrap image urls in url(...)
  				if( /^(http|file|\/\/)/gi.test( data.background ) || /\.(svg|png|jpg|jpeg|gif|bmp)$/gi.test( data.background ) ) {
  					element.style.backgroundImage = 'url('+ data.background +')';
  				}
  				else {
  					element.style.background = data.background;
  				}
  			}
  
  			if( data.background || data.backgroundColor || data.backgroundImage ) {
  				element.setAttribute( 'data-background-hash', data.background + data.backgroundSize + data.backgroundImage + data.backgroundColor + data.backgroundRepeat + data.backgroundPosition + data.backgroundTransition );
  			}
  
  			// Additional and optional background properties
  			if( data.backgroundSize ) element.style.backgroundSize = data.backgroundSize;
  			if( data.backgroundImage ) element.style.backgroundImage = 'url("' + data.backgroundImage + '")';
  			if( data.backgroundColor ) element.style.backgroundColor = data.backgroundColor;
  			if( data.backgroundRepeat ) element.style.backgroundRepeat = data.backgroundRepeat;
  			if( data.backgroundPosition ) element.style.backgroundPosition = data.backgroundPosition;
  			if( data.backgroundTransition ) element.setAttribute( 'data-background-transition', data.backgroundTransition );
  
  			container.appendChild( element );
  
  			return element;
  
  		}
  
  		// Iterate over all horizontal slides
  		toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( slideh ) {
  
  			var backgroundStack;
  
  			if( isPrintingPDF() ) {
  				backgroundStack = _createBackground( slideh, slideh );
  			}
  			else {
  				backgroundStack = _createBackground( slideh, dom.background );
  			}
  
  			// Iterate over all vertical slides
  			toArray( slideh.querySelectorAll( 'section' ) ).forEach( function( slidev ) {
  
  				if( isPrintingPDF() ) {
  					_createBackground( slidev, slidev );
  				}
  				else {
  					_createBackground( slidev, backgroundStack );
  				}
  
  			} );
  
  		} );
  
  		// Add parallax background if specified
  		if( config.parallaxBackgroundImage ) {
  
  			dom.background.style.backgroundImage = 'url("' + config.parallaxBackgroundImage + '")';
  			dom.background.style.backgroundSize = config.parallaxBackgroundSize;
  
  			// Make sure the below properties are set on the element - these properties are
  			// needed for proper transitions to be set on the element via CSS. To remove
  			// annoying background slide-in effect when the presentation starts, apply
  			// these properties after short time delay
  			setTimeout( function() {
  				dom.wrapper.classList.add( 'has-parallax-background' );
  			}, 1 );
  
  		}
  		else {
  
  			dom.background.style.backgroundImage = '';
  			dom.wrapper.classList.remove( 'has-parallax-background' );
  
  		}
  
  	}
  
  	/**
  	 * Applies the configuration settings from the config
  	 * object. May be called multiple times.
  	 */
  	function configure( options ) {
  
  		var numberOfSlides = document.querySelectorAll( SLIDES_SELECTOR ).length;
  
  		dom.wrapper.classList.remove( config.transition );
  
  		// New config options may be passed when this method
  		// is invoked through the API after initialization
  		if( typeof options === 'object' ) extend( config, options );
  
  		// Force linear transition based on browser capabilities
  		if( features.transforms3d === false ) config.transition = 'linear';
  
  		dom.wrapper.classList.add( config.transition );
  
  		dom.wrapper.setAttribute( 'data-transition-speed', config.transitionSpeed );
  		dom.wrapper.setAttribute( 'data-background-transition', config.backgroundTransition );
  
  		dom.controls.style.display = config.controls ? 'block' : 'none';
  		dom.progress.style.display = config.progress ? 'block' : 'none';
  
  		if( config.rtl ) {
  			dom.wrapper.classList.add( 'rtl' );
  		}
  		else {
  			dom.wrapper.classList.remove( 'rtl' );
  		}
  
  		if( config.center ) {
  			dom.wrapper.classList.add( 'center' );
  		}
  		else {
  			dom.wrapper.classList.remove( 'center' );
  		}
  
  		if( config.mouseWheel ) {
  			document.addEventListener( 'DOMMouseScroll', onDocumentMouseScroll, false ); // FF
  			document.addEventListener( 'mousewheel', onDocumentMouseScroll, false );
  		}
  		else {
  			document.removeEventListener( 'DOMMouseScroll', onDocumentMouseScroll, false ); // FF
  			document.removeEventListener( 'mousewheel', onDocumentMouseScroll, false );
  		}
  
  		// Rolling 3D links
  		if( config.rollingLinks ) {
  			enableRollingLinks();
  		}
  		else {
  			disableRollingLinks();
  		}
  
  		// Iframe link previews
  		if( config.previewLinks ) {
  			enablePreviewLinks();
  		}
  		else {
  			disablePreviewLinks();
  			enablePreviewLinks( '[data-preview-link]' );
  		}
  
  		// Auto-slide playback controls
  		if( numberOfSlides > 1 && config.autoSlide && config.autoSlideStoppable && features.canvas && features.requestAnimationFrame ) {
  			autoSlidePlayer = new Playback( dom.wrapper, function() {
  				return Math.min( Math.max( ( Date.now() - autoSlideStartTime ) / autoSlide, 0 ), 1 );
  			} );
  
  			autoSlidePlayer.on( 'click', onAutoSlidePlayerClick );
  			autoSlidePaused = false;
  		}
  		else if( autoSlidePlayer ) {
  			autoSlidePlayer.destroy();
  			autoSlidePlayer = null;
  		}
  
  		// Load the theme in the config, if it's not already loaded
  		if( config.theme && dom.theme ) {
  			var themeURL = dom.theme.getAttribute( 'href' );
  			var themeFinder = /[^\/]*?(?=\.css)/;
  			var themeName = themeURL.match(themeFinder)[0];
  
  			if(  config.theme !== themeName ) {
  				themeURL = themeURL.replace(themeFinder, config.theme);
  				dom.theme.setAttribute( 'href', themeURL );
  			}
  		}
  
  		sync();
  
  	}
  
  	/**
  	 * Binds all event listeners.
  	 */
  	function addEventListeners() {
  
  		eventsAreBound = true;
  
  		window.addEventListener( 'hashchange', onWindowHashChange, false );
  		window.addEventListener( 'resize', onWindowResize, false );
  
  		if( config.touch ) {
  			dom.wrapper.addEventListener( 'touchstart', onTouchStart, false );
  			dom.wrapper.addEventListener( 'touchmove', onTouchMove, false );
  			dom.wrapper.addEventListener( 'touchend', onTouchEnd, false );
  
  			// Support pointer-style touch interaction as well
  			if( window.navigator.msPointerEnabled ) {
  				dom.wrapper.addEventListener( 'MSPointerDown', onPointerDown, false );
  				dom.wrapper.addEventListener( 'MSPointerMove', onPointerMove, false );
  				dom.wrapper.addEventListener( 'MSPointerUp', onPointerUp, false );
  			}
  		}
  
  		if( config.keyboard ) {
  			document.addEventListener( 'keydown', onDocumentKeyDown, false );
  		}
  
  		if( config.progress && dom.progress ) {
  			dom.progress.addEventListener( 'click', onProgressClicked, false );
  		}
  
  		if( config.focusBodyOnPageVisiblityChange ) {
  			var visibilityChange;
  
  			if( 'hidden' in document ) {
  				visibilityChange = 'visibilitychange';
  			}
  			else if( 'msHidden' in document ) {
  				visibilityChange = 'msvisibilitychange';
  			}
  			else if( 'webkitHidden' in document ) {
  				visibilityChange = 'webkitvisibilitychange';
  			}
  
  			if( visibilityChange ) {
  				document.addEventListener( visibilityChange, onPageVisibilityChange, false );
  			}
  		}
  
  		[ 'touchstart', 'click' ].forEach( function( eventName ) {
  			dom.controlsLeft.forEach( function( el ) { el.addEventListener( eventName, onNavigateLeftClicked, false ); } );
  			dom.controlsRight.forEach( function( el ) { el.addEventListener( eventName, onNavigateRightClicked, false ); } );
  			dom.controlsUp.forEach( function( el ) { el.addEventListener( eventName, onNavigateUpClicked, false ); } );
  			dom.controlsDown.forEach( function( el ) { el.addEventListener( eventName, onNavigateDownClicked, false ); } );
  			dom.controlsPrev.forEach( function( el ) { el.addEventListener( eventName, onNavigatePrevClicked, false ); } );
  			dom.controlsNext.forEach( function( el ) { el.addEventListener( eventName, onNavigateNextClicked, false ); } );
  		} );
  
  	}
  
  	/**
  	 * Unbinds all event listeners.
  	 */
  	function removeEventListeners() {
  
  		eventsAreBound = false;
  
  		document.removeEventListener( 'keydown', onDocumentKeyDown, false );
  		window.removeEventListener( 'hashchange', onWindowHashChange, false );
  		window.removeEventListener( 'resize', onWindowResize, false );
  
  		dom.wrapper.removeEventListener( 'touchstart', onTouchStart, false );
  		dom.wrapper.removeEventListener( 'touchmove', onTouchMove, false );
  		dom.wrapper.removeEventListener( 'touchend', onTouchEnd, false );
  
  		if( window.navigator.msPointerEnabled ) {
  			dom.wrapper.removeEventListener( 'MSPointerDown', onPointerDown, false );
  			dom.wrapper.removeEventListener( 'MSPointerMove', onPointerMove, false );
  			dom.wrapper.removeEventListener( 'MSPointerUp', onPointerUp, false );
  		}
  
  		if ( config.progress && dom.progress ) {
  			dom.progress.removeEventListener( 'click', onProgressClicked, false );
  		}
  
  		[ 'touchstart', 'click' ].forEach( function( eventName ) {
  			dom.controlsLeft.forEach( function( el ) { el.removeEventListener( eventName, onNavigateLeftClicked, false ); } );
  			dom.controlsRight.forEach( function( el ) { el.removeEventListener( eventName, onNavigateRightClicked, false ); } );
  			dom.controlsUp.forEach( function( el ) { el.removeEventListener( eventName, onNavigateUpClicked, false ); } );
  			dom.controlsDown.forEach( function( el ) { el.removeEventListener( eventName, onNavigateDownClicked, false ); } );
  			dom.controlsPrev.forEach( function( el ) { el.removeEventListener( eventName, onNavigatePrevClicked, false ); } );
  			dom.controlsNext.forEach( function( el ) { el.removeEventListener( eventName, onNavigateNextClicked, false ); } );
  		} );
  
  	}
  
  	/**
  	 * Extend object a with the properties of object b.
  	 * If there's a conflict, object b takes precedence.
  	 */
  	function extend( a, b ) {
  
  		for( var i in b ) {
  			a[ i ] = b[ i ];
  		}
  
  	}
  
  	/**
  	 * Converts the target object to an array.
  	 */
  	function toArray( o ) {
  
  		return Array.prototype.slice.call( o );
  
  	}
  
  	/**
  	 * Measures the distance in pixels between point a
  	 * and point b.
  	 *
  	 * @param {Object} a point with x/y properties
  	 * @param {Object} b point with x/y properties
  	 */
  	function distanceBetween( a, b ) {
  
  		var dx = a.x - b.x,
  			dy = a.y - b.y;
  
  		return Math.sqrt( dx*dx + dy*dy );
  
  	}
  
  	/**
  	 * Applies a CSS transform to the target element.
  	 */
  	function transformElement( element, transform ) {
  
  		element.style.WebkitTransform = transform;
  		element.style.MozTransform = transform;
  		element.style.msTransform = transform;
  		element.style.OTransform = transform;
  		element.style.transform = transform;
  
  	}
  
  	/**
  	 * Retrieves the height of the given element by looking
  	 * at the position and height of its immediate children.
  	 */
  	function getAbsoluteHeight( element ) {
  
  		var height = 0;
  
  		if( element ) {
  			var absoluteChildren = 0;
  
  			toArray( element.childNodes ).forEach( function( child ) {
  
  				if( typeof child.offsetTop === 'number' && child.style ) {
  					// Count # of abs children
  					if( child.style.position === 'absolute' ) {
  						absoluteChildren += 1;
  					}
  
  					height = Math.max( height, child.offsetTop + child.offsetHeight );
  				}
  
  			} );
  
  			// If there are no absolute children, use offsetHeight
  			if( absoluteChildren === 0 ) {
  				height = element.offsetHeight;
  			}
  
  		}
  
  		return height;
  
  	}
  
  	/**
  	 * Returns the remaining height within the parent of the
  	 * target element after subtracting the height of all
  	 * siblings.
  	 *
  	 * remaining height = [parent height] - [ siblings height]
  	 */
  	function getRemainingHeight( element, height ) {
  
  		height = height || 0;
  
  		if( element ) {
  			var parent = element.parentNode;
  			var siblings = parent.childNodes;
  
  			// Subtract the height of each sibling
  			toArray( siblings ).forEach( function( sibling ) {
  
  				if( typeof sibling.offsetHeight === 'number' && sibling !== element ) {
  
  					var styles = window.getComputedStyle( sibling ),
  						marginTop = parseInt( styles.marginTop, 10 ),
  						marginBottom = parseInt( styles.marginBottom, 10 );
  
  					height -= sibling.offsetHeight + marginTop + marginBottom;
  
  				}
  
  			} );
  
  			var elementStyles = window.getComputedStyle( element );
  
  			// Subtract the margins of the target element
  			height -= parseInt( elementStyles.marginTop, 10 ) +
  						parseInt( elementStyles.marginBottom, 10 );
  
  		}
  
  		return height;
  
  	}
  
  	/**
  	 * Checks if this instance is being used to print a PDF.
  	 */
  	function isPrintingPDF() {
  
  		return ( /print-pdf/gi ).test( window.location.search );
  
  	}
  
  	/**
  	 * Hides the address bar if we're on a mobile device.
  	 */
  	function hideAddressBar() {
  
  		if( config.hideAddressBar && isMobileDevice ) {
  			// Events that should trigger the address bar to hide
  			window.addEventListener( 'load', removeAddressBar, false );
  			window.addEventListener( 'orientationchange', removeAddressBar, false );
  		}
  
  	}
  
  	/**
  	 * Causes the address bar to hide on mobile devices,
  	 * more vertical space ftw.
  	 */
  	function removeAddressBar() {
  
  		setTimeout( function() {
  			window.scrollTo( 0, 1 );
  		}, 10 );
  
  	}
  
  	/**
  	 * Dispatches an event of the specified type from the
  	 * reveal DOM element.
  	 */
  	function dispatchEvent( type, properties ) {
  
  		var event = document.createEvent( "HTMLEvents", 1, 2 );
  		event.initEvent( type, true, true );
  		extend( event, properties );
  		dom.wrapper.dispatchEvent( event );
  
  	}
  
  	/**
  	 * Wrap all links in 3D goodness.
  	 */
  	function enableRollingLinks() {
  
  		if( features.transforms3d && !( 'msPerspective' in document.body.style ) ) {
  			var anchors = document.querySelectorAll( SLIDES_SELECTOR + ' a:not(.image)' );
  
  			for( var i = 0, len = anchors.length; i < len; i++ ) {
  				var anchor = anchors[i];
  
  				if( anchor.textContent && !anchor.querySelector( '*' ) && ( !anchor.className || !anchor.classList.contains( anchor, 'roll' ) ) ) {
  					var span = document.createElement('span');
  					span.setAttribute('data-title', anchor.text);
  					span.innerHTML = anchor.innerHTML;
  
  					anchor.classList.add( 'roll' );
  					anchor.innerHTML = '';
  					anchor.appendChild(span);
  				}
  			}
  		}
  
  	}
  
  	/**
  	 * Unwrap all 3D links.
  	 */
  	function disableRollingLinks() {
  
  		var anchors = document.querySelectorAll( SLIDES_SELECTOR + ' a.roll' );
  
  		for( var i = 0, len = anchors.length; i < len; i++ ) {
  			var anchor = anchors[i];
  			var span = anchor.querySelector( 'span' );
  
  			if( span ) {
  				anchor.classList.remove( 'roll' );
  				anchor.innerHTML = span.innerHTML;
  			}
  		}
  
  	}
  
  	/**
  	 * Bind preview frame links.
  	 */
  	function enablePreviewLinks( selector ) {
  
  		var anchors = toArray( document.querySelectorAll( selector ? selector : 'a' ) );
  
  		anchors.forEach( function( element ) {
  			if( /^(http|www)/gi.test( element.getAttribute( 'href' ) ) ) {
  				element.addEventListener( 'click', onPreviewLinkClicked, false );
  			}
  		} );
  
  	}
  
  	/**
  	 * Unbind preview frame links.
  	 */
  	function disablePreviewLinks() {
  
  		var anchors = toArray( document.querySelectorAll( 'a' ) );
  
  		anchors.forEach( function( element ) {
  			if( /^(http|www)/gi.test( element.getAttribute( 'href' ) ) ) {
  				element.removeEventListener( 'click', onPreviewLinkClicked, false );
  			}
  		} );
  
  	}
  
  	/**
  	 * Opens a preview window for the target URL.
  	 */
  	function openPreview( url ) {
  
  		closePreview();
  
  		dom.preview = document.createElement( 'div' );
  		dom.preview.classList.add( 'preview-link-overlay' );
  		dom.wrapper.appendChild( dom.preview );
  
  		dom.preview.innerHTML = [
  			'<header>',
  				'<a class="close" href="#"><span class="icon"></span></a>',
  				'<a class="external" href="'+ url +'" target="_blank"><span class="icon"></span></a>',
  			'</header>',
  			'<div class="spinner"></div>',
  			'<div class="viewport">',
  				'<iframe src="'+ url +'"></iframe>',
  			'</div>'
  		].join('');
  
  		dom.preview.querySelector( 'iframe' ).addEventListener( 'load', function( event ) {
  			dom.preview.classList.add( 'loaded' );
  		}, false );
  
  		dom.preview.querySelector( '.close' ).addEventListener( 'click', function( event ) {
  			closePreview();
  			event.preventDefault();
  		}, false );
  
  		dom.preview.querySelector( '.external' ).addEventListener( 'click', function( event ) {
  			closePreview();
  		}, false );
  
  		setTimeout( function() {
  			dom.preview.classList.add( 'visible' );
  		}, 1 );
  
  	}
  
  	/**
  	 * Closes the iframe preview window.
  	 */
  	function closePreview() {
  
  		if( dom.preview ) {
  			dom.preview.setAttribute( 'src', '' );
  			dom.preview.parentNode.removeChild( dom.preview );
  			dom.preview = null;
  		}
  
  	}
  
  	/**
  	 * Applies JavaScript-controlled layout rules to the
  	 * presentation.
  	 */
  	function layout() {
  
  		if( dom.wrapper && !isPrintingPDF() ) {
  
  			// Available space to scale within
  			var availableWidth = dom.wrapper.offsetWidth,
  				availableHeight = dom.wrapper.offsetHeight;
  
  			// Reduce available space by margin
  			availableWidth -= ( availableHeight * config.margin );
  			availableHeight -= ( availableHeight * config.margin );
  
  			// Dimensions of the content
  			var slideWidth = config.width,
  				slideHeight = config.height,
  				slidePadding = 20; // TODO Dig this out of DOM
  
  			// Layout the contents of the slides
  			layoutSlideContents( config.width, config.height, slidePadding );
  
  			// Slide width may be a percentage of available width
  			if( typeof slideWidth === 'string' && /%$/.test( slideWidth ) ) {
  				slideWidth = parseInt( slideWidth, 10 ) / 100 * availableWidth;
  			}
  
  			// Slide height may be a percentage of available height
  			if( typeof slideHeight === 'string' && /%$/.test( slideHeight ) ) {
  				slideHeight = parseInt( slideHeight, 10 ) / 100 * availableHeight;
  			}
  
  			dom.slides.style.width = slideWidth + 'px';
  			dom.slides.style.height = slideHeight + 'px';
  
  			// Determine scale of content to fit within available space
  			scale = Math.min( availableWidth / slideWidth, availableHeight / slideHeight );
  
  			// Respect max/min scale settings
  			scale = Math.max( scale, config.minScale );
  			scale = Math.min( scale, config.maxScale );
  
  			// Prefer applying scale via zoom since Chrome blurs scaled content
  			// with nested transforms
  			if( typeof dom.slides.style.zoom !== 'undefined' && !navigator.userAgent.match( /(iphone|ipod|ipad|android)/gi ) ) {
  				dom.slides.style.zoom = scale;
  			}
  			// Apply scale transform as a fallback
  			else {
  				transformElement( dom.slides, 'translate(-50%, -50%) scale('+ scale +') translate(50%, 50%)' );
  			}
  
  			// Select all slides, vertical and horizontal
  			var slides = toArray( document.querySelectorAll( SLIDES_SELECTOR ) );
  
  			for( var i = 0, len = slides.length; i < len; i++ ) {
  				var slide = slides[ i ];
  
  				// Don't bother updating invisible slides
  				if( slide.style.display === 'none' ) {
  					continue;
  				}
  
  				if( config.center || slide.classList.contains( 'center' ) ) {
  					// Vertical stacks are not centred since their section
  					// children will be
  					if( slide.classList.contains( 'stack' ) ) {
  						slide.style.top = 0;
  					}
  					else {
  						slide.style.top = Math.max( - ( getAbsoluteHeight( slide ) / 2 ) - slidePadding, -slideHeight / 2 ) + 'px';
  					}
  				}
  				else {
  					slide.style.top = '';
  				}
  
  			}
  
  			updateProgress();
  			updateParallax();
  
  		}
  
  	}
  
  	/**
  	 * Applies layout logic to the contents of all slides in
  	 * the presentation.
  	 */
  	function layoutSlideContents( width, height, padding ) {
  
  		// Handle sizing of elements with the 'stretch' class
  		toArray( dom.slides.querySelectorAll( 'section > .stretch' ) ).forEach( function( element ) {
  
  			// Determine how much vertical space we can use
  			var remainingHeight = getRemainingHeight( element, ( height - ( padding * 2 ) ) );
  
  			// Consider the aspect ratio of media elements
  			if( /(img|video)/gi.test( element.nodeName ) ) {
  				var nw = element.naturalWidth || element.videoWidth,
  					nh = element.naturalHeight || element.videoHeight;
  
  				var es = Math.min( width / nw, remainingHeight / nh );
  
  				element.style.width = ( nw * es ) + 'px';
  				element.style.height = ( nh * es ) + 'px';
  
  			}
  			else {
  				element.style.width = width + 'px';
  				element.style.height = remainingHeight + 'px';
  			}
  
  		} );
  
  	}
  
  	/**
  	 * Stores the vertical index of a stack so that the same
  	 * vertical slide can be selected when navigating to and
  	 * from the stack.
  	 *
  	 * @param {HTMLElement} stack The vertical stack element
  	 * @param {int} v Index to memorize
  	 */
  	function setPreviousVerticalIndex( stack, v ) {
  
  		if( typeof stack === 'object' && typeof stack.setAttribute === 'function' ) {
  			stack.setAttribute( 'data-previous-indexv', v || 0 );
  		}
  
  	}
  
  	/**
  	 * Retrieves the vertical index which was stored using
  	 * #setPreviousVerticalIndex() or 0 if no previous index
  	 * exists.
  	 *
  	 * @param {HTMLElement} stack The vertical stack element
  	 */
  	function getPreviousVerticalIndex( stack ) {
  
  		if( typeof stack === 'object' && typeof stack.setAttribute === 'function' && stack.classList.contains( 'stack' ) ) {
  			// Prefer manually defined start-indexv
  			var attributeName = stack.hasAttribute( 'data-start-indexv' ) ? 'data-start-indexv' : 'data-previous-indexv';
  
  			return parseInt( stack.getAttribute( attributeName ) || 0, 10 );
  		}
  
  		return 0;
  
  	}
  
  	/**
  	 * Displays the overview of slides (quick nav) by
  	 * scaling down and arranging all slide elements.
  	 *
  	 * Experimental feature, might be dropped if perf
  	 * can't be improved.
  	 */
  	function activateOverview() {
  
  		// Only proceed if enabled in config
  		if( config.overview ) {
  
  			// Don't auto-slide while in overview mode
  			cancelAutoSlide();
  
  			var wasActive = dom.wrapper.classList.contains( 'overview' );
  
  			// Vary the depth of the overview based on screen size
  			var depth = window.innerWidth < 400 ? 1000 : 2500;
  
  			dom.wrapper.classList.add( 'overview' );
  			dom.wrapper.classList.remove( 'overview-deactivating' );
  
  			clearTimeout( activateOverviewTimeout );
  			clearTimeout( deactivateOverviewTimeout );
  
  			// Not the pretties solution, but need to let the overview
  			// class apply first so that slides are measured accurately
  			// before we can position them
  			activateOverviewTimeout = setTimeout( function() {
  
  				var horizontalSlides = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR );
  
  				for( var i = 0, len1 = horizontalSlides.length; i < len1; i++ ) {
  					var hslide = horizontalSlides[i],
  						hoffset = config.rtl ? -105 : 105;
  
  					hslide.setAttribute( 'data-index-h', i );
  
  					// Apply CSS transform
  					transformElement( hslide, 'translateZ(-'+ depth +'px) translate(' + ( ( i - indexh ) * hoffset ) + '%, 0%)' );
  
  					if( hslide.classList.contains( 'stack' ) ) {
  
  						var verticalSlides = hslide.querySelectorAll( 'section' );
  
  						for( var j = 0, len2 = verticalSlides.length; j < len2; j++ ) {
  							var verticalIndex = i === indexh ? indexv : getPreviousVerticalIndex( hslide );
  
  							var vslide = verticalSlides[j];
  
  							vslide.setAttribute( 'data-index-h', i );
  							vslide.setAttribute( 'data-index-v', j );
  
  							// Apply CSS transform
  							transformElement( vslide, 'translate(0%, ' + ( ( j - verticalIndex ) * 105 ) + '%)' );
  
  							// Navigate to this slide on click
  							vslide.addEventListener( 'click', onOverviewSlideClicked, true );
  						}
  
  					}
  					else {
  
  						// Navigate to this slide on click
  						hslide.addEventListener( 'click', onOverviewSlideClicked, true );
  
  					}
  				}
  
  				updateSlidesVisibility();
  
  				layout();
  
  				if( !wasActive ) {
  					// Notify observers of the overview showing
  					dispatchEvent( 'overviewshown', {
  						'indexh': indexh,
  						'indexv': indexv,
  						'currentSlide': currentSlide
  					} );
  				}
  
  			}, 10 );
  
  		}
  
  	}
  
  	/**
  	 * Exits the slide overview and enters the currently
  	 * active slide.
  	 */
  	function deactivateOverview() {
  
  		// Only proceed if enabled in config
  		if( config.overview ) {
  
  			clearTimeout( activateOverviewTimeout );
  			clearTimeout( deactivateOverviewTimeout );
  
  			dom.wrapper.classList.remove( 'overview' );
  
  			// Temporarily add a class so that transitions can do different things
  			// depending on whether they are exiting/entering overview, or just
  			// moving from slide to slide
  			dom.wrapper.classList.add( 'overview-deactivating' );
  
  			deactivateOverviewTimeout = setTimeout( function () {
  				dom.wrapper.classList.remove( 'overview-deactivating' );
  			}, 1 );
  
  			// Select all slides
  			toArray( document.querySelectorAll( SLIDES_SELECTOR ) ).forEach( function( slide ) {
  				// Resets all transforms to use the external styles
  				transformElement( slide, '' );
  
  				slide.removeEventListener( 'click', onOverviewSlideClicked, true );
  			} );
  
  			slide( indexh, indexv );
  
  			cueAutoSlide();
  
  			// Notify observers of the overview hiding
  			dispatchEvent( 'overviewhidden', {
  				'indexh': indexh,
  				'indexv': indexv,
  				'currentSlide': currentSlide
  			} );
  
  		}
  	}
  
  	/**
  	 * Toggles the slide overview mode on and off.
  	 *
  	 * @param {Boolean} override Optional flag which overrides the
  	 * toggle logic and forcibly sets the desired state. True means
  	 * overview is open, false means it's closed.
  	 */
  	function toggleOverview( override ) {
  
  		if( typeof override === 'boolean' ) {
  			override ? activateOverview() : deactivateOverview();
  		}
  		else {
  			isOverview() ? deactivateOverview() : activateOverview();
  		}
  
  	}
  
  	/**
  	 * Checks if the overview is currently active.
  	 *
  	 * @return {Boolean} true if the overview is active,
  	 * false otherwise
  	 */
  	function isOverview() {
  
  		return dom.wrapper.classList.contains( 'overview' );
  
  	}
  
  	/**
  	 * Checks if the current or specified slide is vertical
  	 * (nested within another slide).
  	 *
  	 * @param {HTMLElement} slide [optional] The slide to check
  	 * orientation of
  	 */
  	function isVerticalSlide( slide ) {
  
  		// Prefer slide argument, otherwise use current slide
  		slide = slide ? slide : currentSlide;
  
  		return slide && slide.parentNode && !!slide.parentNode.nodeName.match( /section/i );
  
  	}
  
  	/**
  	 * Handling the fullscreen functionality via the fullscreen API
  	 *
  	 * @see http://fullscreen.spec.whatwg.org/
  	 * @see https://developer.mozilla.org/en-US/docs/DOM/Using_fullscreen_mode
  	 */
  	function enterFullscreen() {
  
  		var element = document.body;
  
  		// Check which implementation is available
  		var requestMethod = element.requestFullScreen ||
  							element.webkitRequestFullscreen ||
  							element.webkitRequestFullScreen ||
  							element.mozRequestFullScreen ||
  							element.msRequestFullScreen;
  
  		if( requestMethod ) {
  			requestMethod.apply( element );
  		}
  
  	}
  
  	/**
  	 * Enters the paused mode which fades everything on screen to
  	 * black.
  	 */
  	function pause() {
  
  		var wasPaused = dom.wrapper.classList.contains( 'paused' );
  
  		cancelAutoSlide();
  		dom.wrapper.classList.add( 'paused' );
  
  		if( wasPaused === false ) {
  			dispatchEvent( 'paused' );
  		}
  
  	}
  
  	/**
  	 * Exits from the paused mode.
  	 */
  	function resume() {
  
  		var wasPaused = dom.wrapper.classList.contains( 'paused' );
  		dom.wrapper.classList.remove( 'paused' );
  
  		cueAutoSlide();
  
  		if( wasPaused ) {
  			dispatchEvent( 'resumed' );
  		}
  
  	}
  
  	/**
  	 * Toggles the paused mode on and off.
  	 */
  	function togglePause() {
  
  		if( isPaused() ) {
  			resume();
  		}
  		else {
  			pause();
  		}
  
  	}
  
  	/**
  	 * Checks if we are currently in the paused mode.
  	 */
  	function isPaused() {
  
  		return dom.wrapper.classList.contains( 'paused' );
  
  	}
  
  	/**
  	 * Steps from the current point in the presentation to the
  	 * slide which matches the specified horizontal and vertical
  	 * indices.
  	 *
  	 * @param {int} h Horizontal index of the target slide
  	 * @param {int} v Vertical index of the target slide
  	 * @param {int} f Optional index of a fragment within the
  	 * target slide to activate
  	 * @param {int} o Optional origin for use in multimaster environments
  	 */
  	function slide( h, v, f, o ) {
  
  		// Remember where we were at before
  		previousSlide = currentSlide;
  
  		// Query all horizontal slides in the deck
  		var horizontalSlides = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR );
  
  		// If no vertical index is specified and the upcoming slide is a
  		// stack, resume at its previous vertical index
  		if( v === undefined ) {
  			v = getPreviousVerticalIndex( horizontalSlides[ h ] );
  		}
  
  		// If we were on a vertical stack, remember what vertical index
  		// it was on so we can resume at the same position when returning
  		if( previousSlide && previousSlide.parentNode && previousSlide.parentNode.classList.contains( 'stack' ) ) {
  			setPreviousVerticalIndex( previousSlide.parentNode, indexv );
  		}
  
  		// Remember the state before this slide
  		var stateBefore = state.concat();
  
  		// Reset the state array
  		state.length = 0;
  
  		var indexhBefore = indexh || 0,
  			indexvBefore = indexv || 0;
  
  		// Activate and transition to the new slide
  		indexh = updateSlides( HORIZONTAL_SLIDES_SELECTOR, h === undefined ? indexh : h );
  		indexv = updateSlides( VERTICAL_SLIDES_SELECTOR, v === undefined ? indexv : v );
  
  		// Update the visibility of slides now that the indices have changed
  		updateSlidesVisibility();
  
  		layout();
  
  		// Apply the new state
  		stateLoop: for( var i = 0, len = state.length; i < len; i++ ) {
  			// Check if this state existed on the previous slide. If it
  			// did, we will avoid adding it repeatedly
  			for( var j = 0; j < stateBefore.length; j++ ) {
  				if( stateBefore[j] === state[i] ) {
  					stateBefore.splice( j, 1 );
  					continue stateLoop;
  				}
  			}
  
  			document.documentElement.classList.add( state[i] );
  
  			// Dispatch custom event matching the state's name
  			dispatchEvent( state[i] );
  		}
  
  		// Clean up the remains of the previous state
  		while( stateBefore.length ) {
  			document.documentElement.classList.remove( stateBefore.pop() );
  		}
  
  		// If the overview is active, re-activate it to update positions
  		if( isOverview() ) {
  			activateOverview();
  		}
  
  		// Find the current horizontal slide and any possible vertical slides
  		// within it
  		var currentHorizontalSlide = horizontalSlides[ indexh ],
  			currentVerticalSlides = currentHorizontalSlide.querySelectorAll( 'section' );
  
  		// Store references to the previous and current slides
  		currentSlide = currentVerticalSlides[ indexv ] || currentHorizontalSlide;
  
  		// Show fragment, if specified
  		if( typeof f !== 'undefined' ) {
  			navigateFragment( f );
  		}
  
  		// Dispatch an event if the slide changed
  		var slideChanged = ( indexh !== indexhBefore || indexv !== indexvBefore );
  		if( slideChanged ) {
  			dispatchEvent( 'slidechanged', {
  				'indexh': indexh,
  				'indexv': indexv,
  				'previousSlide': previousSlide,
  				'currentSlide': currentSlide,
  				'origin': o
  			} );
  		}
  		else {
  			// Ensure that the previous slide is never the same as the current
  			previousSlide = null;
  		}
  
  		// Solves an edge case where the previous slide maintains the
  		// 'present' class when navigating between adjacent vertical
  		// stacks
  		if( previousSlide ) {
  			previousSlide.classList.remove( 'present' );
  
  			// Reset all slides upon navigate to home
  			// Issue: #285
  			if ( document.querySelector( HOME_SLIDE_SELECTOR ).classList.contains( 'present' ) ) {
  				// Launch async task
  				setTimeout( function () {
  					var slides = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.stack') ), i;
  					for( i in slides ) {
  						if( slides[i] ) {
  							// Reset stack
  							setPreviousVerticalIndex( slides[i], 0 );
  						}
  					}
  				}, 0 );
  			}
  		}
  
  		// Handle embedded content
  		if( slideChanged ) {
  			stopEmbeddedContent( previousSlide );
  			startEmbeddedContent( currentSlide );
  		}
  
  		updateControls();
  		updateProgress();
  		updateBackground();
  		updateParallax();
  		updateSlideNumber();
  
  		// Update the URL hash
  		writeURL();
  
  		cueAutoSlide();
  
  	}
  
  	/**
  	 * Syncs the presentation with the current DOM. Useful
  	 * when new slides or control elements are added or when
  	 * the configuration has changed.
  	 */
  	function sync() {
  
  		// Subscribe to input
  		removeEventListeners();
  		addEventListeners();
  
  		// Force a layout to make sure the current config is accounted for
  		layout();
  
  		// Reflect the current autoSlide value
  		autoSlide = config.autoSlide;
  
  		// Start auto-sliding if it's enabled
  		cueAutoSlide();
  
  		// Re-create the slide backgrounds
  		createBackgrounds();
  
  		sortAllFragments();
  
  		updateControls();
  		updateProgress();
  		updateBackground( true );
  		updateSlideNumber();
  
  	}
  
  	/**
  	 * Resets all vertical slides so that only the first
  	 * is visible.
  	 */
  	function resetVerticalSlides() {
  
  		var horizontalSlides = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
  		horizontalSlides.forEach( function( horizontalSlide ) {
  
  			var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) );
  			verticalSlides.forEach( function( verticalSlide, y ) {
  
  				if( y > 0 ) {
  					verticalSlide.classList.remove( 'present' );
  					verticalSlide.classList.remove( 'past' );
  					verticalSlide.classList.add( 'future' );
  				}
  
  			} );
  
  		} );
  
  	}
  
  	/**
  	 * Sorts and formats all of fragments in the
  	 * presentation.
  	 */
  	function sortAllFragments() {
  
  		var horizontalSlides = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
  		horizontalSlides.forEach( function( horizontalSlide ) {
  
  			var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) );
  			verticalSlides.forEach( function( verticalSlide, y ) {
  
  				sortFragments( verticalSlide.querySelectorAll( '.fragment' ) );
  
  			} );
  
  			if( verticalSlides.length === 0 ) sortFragments( horizontalSlide.querySelectorAll( '.fragment' ) );
  
  		} );
  
  	}
  
  	/**
  	 * Updates one dimension of slides by showing the slide
  	 * with the specified index.
  	 *
  	 * @param {String} selector A CSS selector that will fetch
  	 * the group of slides we are working with
  	 * @param {Number} index The index of the slide that should be
  	 * shown
  	 *
  	 * @return {Number} The index of the slide that is now shown,
  	 * might differ from the passed in index if it was out of
  	 * bounds.
  	 */
  	function updateSlides( selector, index ) {
  
  		// Select all slides and convert the NodeList result to
  		// an array
  		var slides = toArray( document.querySelectorAll( selector ) ),
  			slidesLength = slides.length;
  
  		if( slidesLength ) {
  
  			// Should the index loop?
  			if( config.loop ) {
  				index %= slidesLength;
  
  				if( index < 0 ) {
  					index = slidesLength + index;
  				}
  			}
  
  			// Enforce max and minimum index bounds
  			index = Math.max( Math.min( index, slidesLength - 1 ), 0 );
  
  			for( var i = 0; i < slidesLength; i++ ) {
  				var element = slides[i];
  
  				var reverse = config.rtl && !isVerticalSlide( element );
  
  				element.classList.remove( 'past' );
  				element.classList.remove( 'present' );
  				element.classList.remove( 'future' );
  
  				// http://www.w3.org/html/wg/drafts/html/master/editing.html#the-hidden-attribute
  				element.setAttribute( 'hidden', '' );
  
  				if( i < index ) {
  					// Any element previous to index is given the 'past' class
  					element.classList.add( reverse ? 'future' : 'past' );
  
  					var pastFragments = toArray( element.querySelectorAll( '.fragment' ) );
  
  					// Show all fragments on prior slides
  					while( pastFragments.length ) {
  						var pastFragment = pastFragments.pop();
  						pastFragment.classList.add( 'visible' );
  						pastFragment.classList.remove( 'current-fragment' );
  					}
  				}
  				else if( i > index ) {
  					// Any element subsequent to index is given the 'future' class
  					element.classList.add( reverse ? 'past' : 'future' );
  
  					var futureFragments = toArray( element.querySelectorAll( '.fragment.visible' ) );
  
  					// No fragments in future slides should be visible ahead of time
  					while( futureFragments.length ) {
  						var futureFragment = futureFragments.pop();
  						futureFragment.classList.remove( 'visible' );
  						futureFragment.classList.remove( 'current-fragment' );
  					}
  				}
  
  				// If this element contains vertical slides
  				if( element.querySelector( 'section' ) ) {
  					element.classList.add( 'stack' );
  				}
  			}
  
  			// Mark the current slide as present
  			slides[index].classList.add( 'present' );
  			slides[index].removeAttribute( 'hidden' );
  
  			// If this slide has a state associated with it, add it
  			// onto the current state of the deck
  			var slideState = slides[index].getAttribute( 'data-state' );
  			if( slideState ) {
  				state = state.concat( slideState.split( ' ' ) );
  			}
  
  		}
  		else {
  			// Since there are no slides we can't be anywhere beyond the
  			// zeroth index
  			index = 0;
  		}
  
  		return index;
  
  	}
  
  	/**
  	 * Optimization method; hide all slides that are far away
  	 * from the present slide.
  	 */
  	function updateSlidesVisibility() {
  
  		// Select all slides and convert the NodeList result to
  		// an array
  		var horizontalSlides = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ),
  			horizontalSlidesLength = horizontalSlides.length,
  			distanceX,
  			distanceY;
  
  		if( horizontalSlidesLength ) {
  
  			// The number of steps away from the present slide that will
  			// be visible
  			var viewDistance = isOverview() ? 10 : config.viewDistance;
  
  			// Limit view distance on weaker devices
  			if( isMobileDevice ) {
  				viewDistance = isOverview() ? 6 : 1;
  			}
  
  			for( var x = 0; x < horizontalSlidesLength; x++ ) {
  				var horizontalSlide = horizontalSlides[x];
  
  				var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) ),
  					verticalSlidesLength = verticalSlides.length;
  
  				// Loops so that it measures 1 between the first and last slides
  				distanceX = Math.abs( ( indexh - x ) % ( horizontalSlidesLength - viewDistance ) ) || 0;
  
  				// Show the horizontal slide if it's within the view distance
  				horizontalSlide.style.display = distanceX > viewDistance ? 'none' : 'block';
  
  				if( verticalSlidesLength ) {
  
  					var oy = getPreviousVerticalIndex( horizontalSlide );
  
  					for( var y = 0; y < verticalSlidesLength; y++ ) {
  						var verticalSlide = verticalSlides[y];
  
  						distanceY = x === indexh ? Math.abs( indexv - y ) : Math.abs( y - oy );
  
  						verticalSlide.style.display = ( distanceX + distanceY ) > viewDistance ? 'none' : 'block';
  					}
  
  				}
  			}
  
  		}
  
  	}
  
  	/**
  	 * Updates the progress bar to reflect the current slide.
  	 */
  	function updateProgress() {
  
  		// Update progress if enabled
  		if( config.progress && dom.progress ) {
  
  			var horizontalSlides = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
  
  			// The number of past and total slides
  			var totalCount = document.querySelectorAll( SLIDES_SELECTOR + ':not(.stack)' ).length;
  			var pastCount = 0;
  
  			// Step through all slides and count the past ones
  			mainLoop: for( var i = 0; i < horizontalSlides.length; i++ ) {
  
  				var horizontalSlide = horizontalSlides[i];
  				var verticalSlides = toArray( horizontalSlide.querySelectorAll( 'section' ) );
  
  				for( var j = 0; j < verticalSlides.length; j++ ) {
  
  					// Stop as soon as we arrive at the present
  					if( verticalSlides[j].classList.contains( 'present' ) ) {
  						break mainLoop;
  					}
  
  					pastCount++;
  
  				}
  
  				// Stop as soon as we arrive at the present
  				if( horizontalSlide.classList.contains( 'present' ) ) {
  					break;
  				}
  
  				// Don't count the wrapping section for vertical slides
  				if( horizontalSlide.classList.contains( 'stack' ) === false ) {
  					pastCount++;
  				}
  
  			}
  
  			dom.progressbar.style.width = ( pastCount / ( totalCount - 1 ) ) * window.innerWidth + 'px';
  
  		}
  
  	}
  
  	/**
  	 * Updates the slide number div to reflect the current slide.
  	 */
  	function updateSlideNumber() {
  
  		// Update slide number if enabled
  		if( config.slideNumber && dom.slideNumber) {
  
  			// Display the number of the page using 'indexh - indexv' format
  			var indexString = indexh;
  			if( indexv > 0 ) {
  				indexString += ' - ' + indexv;
  			}
  
  			dom.slideNumber.innerHTML = indexString;
  		}
  
  	}
  
  	/**
  	 * Updates the state of all control/navigation arrows.
  	 */
  	function updateControls() {
  
  		var routes = availableRoutes();
  		var fragments = availableFragments();
  
  		// Remove the 'enabled' class from all directions
  		dom.controlsLeft.concat( dom.controlsRight )
  						.concat( dom.controlsUp )
  						.concat( dom.controlsDown )
  						.concat( dom.controlsPrev )
  						.concat( dom.controlsNext ).forEach( function( node ) {
  			node.classList.remove( 'enabled' );
  			node.classList.remove( 'fragmented' );
  		} );
  
  		// Add the 'enabled' class to the available routes
  		if( routes.left ) dom.controlsLeft.forEach( function( el ) { el.classList.add( 'enabled' );	} );
  		if( routes.right ) dom.controlsRight.forEach( function( el ) { el.classList.add( 'enabled' ); } );
  		if( routes.up ) dom.controlsUp.forEach( function( el ) { el.classList.add( 'enabled' );	} );
  		if( routes.down ) dom.controlsDown.forEach( function( el ) { el.classList.add( 'enabled' ); } );
  
  		// Prev/next buttons
  		if( routes.left || routes.up ) dom.controlsPrev.forEach( function( el ) { el.classList.add( 'enabled' ); } );
  		if( routes.right || routes.down ) dom.controlsNext.forEach( function( el ) { el.classList.add( 'enabled' ); } );
  
  		// Highlight fragment directions
  		if( currentSlide ) {
  
  			// Always apply fragment decorator to prev/next buttons
  			if( fragments.prev ) dom.controlsPrev.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
  			if( fragments.next ) dom.controlsNext.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
  
  			// Apply fragment decorators to directional buttons based on
  			// what slide axis they are in
  			if( isVerticalSlide( currentSlide ) ) {
  				if( fragments.prev ) dom.controlsUp.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
  				if( fragments.next ) dom.controlsDown.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
  			}
  			else {
  				if( fragments.prev ) dom.controlsLeft.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
  				if( fragments.next ) dom.controlsRight.forEach( function( el ) { el.classList.add( 'fragmented', 'enabled' ); } );
  			}
  
  		}
  
  	}
  
  	/**
  	 * Updates the background elements to reflect the current
  	 * slide.
  	 *
  	 * @param {Boolean} includeAll If true, the backgrounds of
  	 * all vertical slides (not just the present) will be updated.
  	 */
  	function updateBackground( includeAll ) {
  
  		var currentBackground = null;
  
  		// Reverse past/future classes when in RTL mode
  		var horizontalPast = config.rtl ? 'future' : 'past',
  			horizontalFuture = config.rtl ? 'past' : 'future';
  
  		// Update the classes of all backgrounds to match the
  		// states of their slides (past/present/future)
  		toArray( dom.background.childNodes ).forEach( function( backgroundh, h ) {
  
  			if( h < indexh ) {
  				backgroundh.className = 'slide-background ' + horizontalPast;
  			}
  			else if ( h > indexh ) {
  				backgroundh.className = 'slide-background ' + horizontalFuture;
  			}
  			else {
  				backgroundh.className = 'slide-background present';
  
  				// Store a reference to the current background element
  				currentBackground = backgroundh;
  			}
  
  			if( includeAll || h === indexh ) {
  				toArray( backgroundh.childNodes ).forEach( function( backgroundv, v ) {
  
  					if( v < indexv ) {
  						backgroundv.className = 'slide-background past';
  					}
  					else if ( v > indexv ) {
  						backgroundv.className = 'slide-background future';
  					}
  					else {
  						backgroundv.className = 'slide-background present';
  
  						// Only if this is the present horizontal and vertical slide
  						if( h === indexh ) currentBackground = backgroundv;
  					}
  
  				} );
  			}
  
  		} );
  
  		// Don't transition between identical backgrounds. This
  		// prevents unwanted flicker.
  		if( currentBackground ) {
  			var previousBackgroundHash = previousBackground ? previousBackground.getAttribute( 'data-background-hash' ) : null;
  			var currentBackgroundHash = currentBackground.getAttribute( 'data-background-hash' );
  			if( currentBackgroundHash && currentBackgroundHash === previousBackgroundHash && currentBackground !== previousBackground ) {
  				dom.background.classList.add( 'no-transition' );
  			}
  
  			previousBackground = currentBackground;
  		}
  
  		// Allow the first background to apply without transition
  		setTimeout( function() {
  			dom.background.classList.remove( 'no-transition' );
  		}, 1 );
  
  	}
  
  	/**
  	 * Updates the position of the parallax background based
  	 * on the current slide index.
  	 */
  	function updateParallax() {
  
  		if( config.parallaxBackgroundImage ) {
  
  			var horizontalSlides = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
  				verticalSlides = document.querySelectorAll( VERTICAL_SLIDES_SELECTOR );
  
  			var backgroundSize = dom.background.style.backgroundSize.split( ' ' ),
  				backgroundWidth, backgroundHeight;
  
  			if( backgroundSize.length === 1 ) {
  				backgroundWidth = backgroundHeight = parseInt( backgroundSize[0], 10 );
  			}
  			else {
  				backgroundWidth = parseInt( backgroundSize[0], 10 );
  				backgroundHeight = parseInt( backgroundSize[1], 10 );
  			}
  
  			var slideWidth = dom.background.offsetWidth;
  			var horizontalSlideCount = horizontalSlides.length;
  			var horizontalOffset = -( backgroundWidth - slideWidth ) / ( horizontalSlideCount-1 ) * indexh;
  
  			var slideHeight = dom.background.offsetHeight;
  			var verticalSlideCount = verticalSlides.length;
  			var verticalOffset = verticalSlideCount > 0 ? -( backgroundHeight - slideHeight ) / ( verticalSlideCount-1 ) * indexv : 0;
  
  			dom.background.style.backgroundPosition = horizontalOffset + 'px ' + verticalOffset + 'px';
  
  		}
  
  	}
  
  	/**
  	 * Determine what available routes there are for navigation.
  	 *
  	 * @return {Object} containing four booleans: left/right/up/down
  	 */
  	function availableRoutes() {
  
  		var horizontalSlides = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
  			verticalSlides = document.querySelectorAll( VERTICAL_SLIDES_SELECTOR );
  
  		var routes = {
  			left: indexh > 0 || config.loop,
  			right: indexh < horizontalSlides.length - 1 || config.loop,
  			up: indexv > 0,
  			down: indexv < verticalSlides.length - 1
  		};
  
  		// reverse horizontal controls for rtl
  		if( config.rtl ) {
  			var left = routes.left;
  			routes.left = routes.right;
  			routes.right = left;
  		}
  
  		return routes;
  
  	}
  
  	/**
  	 * Returns an object describing the available fragment
  	 * directions.
  	 *
  	 * @return {Object} two boolean properties: prev/next
  	 */
  	function availableFragments() {
  
  		if( currentSlide && config.fragments ) {
  			var fragments = currentSlide.querySelectorAll( '.fragment' );
  			var hiddenFragments = currentSlide.querySelectorAll( '.fragment:not(.visible)' );
  
  			return {
  				prev: fragments.length - hiddenFragments.length > 0,
  				next: !!hiddenFragments.length
  			};
  		}
  		else {
  			return { prev: false, next: false };
  		}
  
  	}
  
  	/**
  	 * Start playback of any embedded content inside of
  	 * the targeted slide.
  	 */
  	function startEmbeddedContent( slide ) {
  
  		if( slide && !isSpeakerNotes() ) {
  			// HTML5 media elements
  			toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
  				if( el.hasAttribute( 'data-autoplay' ) ) {
  					el.play();
  				}
  			} );
  
  			// iframe embeds
  			toArray( slide.querySelectorAll( 'iframe' ) ).forEach( function( el ) {
  				el.contentWindow.postMessage( 'slide:start', '*' );
  			});
  
  			// YouTube embeds
  			toArray( slide.querySelectorAll( 'iframe[src*="youtube.com/embed/"]' ) ).forEach( function( el ) {
  				if( el.hasAttribute( 'data-autoplay' ) ) {
  					el.contentWindow.postMessage( '{"event":"command","func":"playVideo","args":""}', '*' );
  				}
  			});
  		}
  
  	}
  
  	/**
  	 * Stop playback of any embedded content inside of
  	 * the targeted slide.
  	 */
  	function stopEmbeddedContent( slide ) {
  
  		if( slide ) {
  			// HTML5 media elements
  			toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
  				if( !el.hasAttribute( 'data-ignore' ) ) {
  					el.pause();
  				}
  			} );
  
  			// iframe embeds
  			toArray( slide.querySelectorAll( 'iframe' ) ).forEach( function( el ) {
  				el.contentWindow.postMessage( 'slide:stop', '*' );
  			});
  
  			// YouTube embeds
  			toArray( slide.querySelectorAll( 'iframe[src*="youtube.com/embed/"]' ) ).forEach( function( el ) {
  				if( !el.hasAttribute( 'data-ignore' ) && typeof el.contentWindow.postMessage === 'function' ) {
  					el.contentWindow.postMessage( '{"event":"command","func":"pauseVideo","args":""}', '*' );
  				}
  			});
  		}
  
  	}
  
  	/**
  	 * Checks if this presentation is running inside of the
  	 * speaker notes window.
  	 */
  	function isSpeakerNotes() {
  
  		return !!window.location.search.match( /receiver/gi );
  
  	}
  
  	/**
  	 * Reads the current URL (hash) and navigates accordingly.
  	 */
  	function readURL() {
  
  		var hash = window.location.hash;
  
  		// Attempt to parse the hash as either an index or name
  		var bits = hash.slice( 2 ).split( '/' ),
  			name = hash.replace( /#|\//gi, '' );
  
  		// If the first bit is invalid and there is a name we can
  		// assume that this is a named link
  		if( isNaN( parseInt( bits[0], 10 ) ) && name.length ) {
  			// Find the slide with the specified name
  			var element = document.querySelector( '#' + name );
  
  			if( element ) {
  				// Find the position of the named slide and navigate to it
  				var indices = Reveal.getIndices( element );
  				slide( indices.h, indices.v );
  			}
  			// If the slide doesn't exist, navigate to the current slide
  			else {
  				slide( indexh || 0, indexv || 0 );
  			}
  		}
  		else {
  			// Read the index components of the hash
  			var h = parseInt( bits[0], 10 ) || 0,
  				v = parseInt( bits[1], 10 ) || 0;
  
  			if( h !== indexh || v !== indexv ) {
  				slide( h, v );
  			}
  		}
  
  	}
  
  	/**
  	 * Updates the page URL (hash) to reflect the current
  	 * state.
  	 *
  	 * @param {Number} delay The time in ms to wait before
  	 * writing the hash
  	 */
  	function writeURL( delay ) {
  
  		if( config.history ) {
  
  			// Make sure there's never more than one timeout running
  			clearTimeout( writeURLTimeout );
  
  			// If a delay is specified, timeout this call
  			if( typeof delay === 'number' ) {
  				writeURLTimeout = setTimeout( writeURL, delay );
  			}
  			else {
  				var url = '/';
  
  				// If the current slide has an ID, use that as a named link
  				if( currentSlide && typeof currentSlide.getAttribute( 'id' ) === 'string' ) {
  					url = '/' + currentSlide.getAttribute( 'id' );
  				}
  				// Otherwise use the /h/v index
  				else {
  					if( indexh > 0 || indexv > 0 ) url += indexh;
  					if( indexv > 0 ) url += '/' + indexv;
  				}
  
  				window.location.hash = url;
  			}
  		}
  
  	}
  
  	/**
  	 * Retrieves the h/v location of the current, or specified,
  	 * slide.
  	 *
  	 * @param {HTMLElement} slide If specified, the returned
  	 * index will be for this slide rather than the currently
  	 * active one
  	 *
  	 * @return {Object} { h: <int>, v: <int>, f: <int> }
  	 */
  	function getIndices( slide ) {
  
  		// By default, return the current indices
  		var h = indexh,
  			v = indexv,
  			f;
  
  		// If a slide is specified, return the indices of that slide
  		if( slide ) {
  			var isVertical = isVerticalSlide( slide );
  			var slideh = isVertical ? slide.parentNode : slide;
  
  			// Select all horizontal slides
  			var horizontalSlides = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
  
  			// Now that we know which the horizontal slide is, get its index
  			h = Math.max( horizontalSlides.indexOf( slideh ), 0 );
  
  			// If this is a vertical slide, grab the vertical index
  			if( isVertical ) {
  				v = Math.max( toArray( slide.parentNode.querySelectorAll( 'section' ) ).indexOf( slide ), 0 );
  			}
  		}
  
  		if( !slide && currentSlide ) {
  			var hasFragments = currentSlide.querySelectorAll( '.fragment' ).length > 0;
  			if( hasFragments ) {
  				var visibleFragments = currentSlide.querySelectorAll( '.fragment.visible' );
  				f = visibleFragments.length - 1;
  			}
  		}
  
  		return { h: h, v: v, f: f };
  
  	}
  
  	/**
  	 * Return a sorted fragments list, ordered by an increasing
  	 * "data-fragment-index" attribute.
  	 *
  	 * Fragments will be revealed in the order that they are returned by
  	 * this function, so you can use the index attributes to control the
  	 * order of fragment appearance.
  	 *
  	 * To maintain a sensible default fragment order, fragments are presumed
  	 * to be passed in document order. This function adds a "fragment-index"
  	 * attribute to each node if such an attribute is not already present,
  	 * and sets that attribute to an integer value which is the position of
  	 * the fragment within the fragments list.
  	 */
  	function sortFragments( fragments ) {
  
  		fragments = toArray( fragments );
  
  		var ordered = [],
  			unordered = [],
  			sorted = [];
  
  		// Group ordered and unordered elements
  		fragments.forEach( function( fragment, i ) {
  			if( fragment.hasAttribute( 'data-fragment-index' ) ) {
  				var index = parseInt( fragment.getAttribute( 'data-fragment-index' ), 10 );
  
  				if( !ordered[index] ) {
  					ordered[index] = [];
  				}
  
  				ordered[index].push( fragment );
  			}
  			else {
  				unordered.push( [ fragment ] );
  			}
  		} );
  
  		// Append fragments without explicit indices in their
  		// DOM order
  		ordered = ordered.concat( unordered );
  
  		// Manually count the index up per group to ensure there
  		// are no gaps
  		var index = 0;
  
  		// Push all fragments in their sorted order to an array,
  		// this flattens the groups
  		ordered.forEach( function( group ) {
  			group.forEach( function( fragment ) {
  				sorted.push( fragment );
  				fragment.setAttribute( 'data-fragment-index', index );
  			} );
  
  			index ++;
  		} );
  
  		return sorted;
  
  	}
  
  	/**
  	 * Navigate to the specified slide fragment.
  	 *
  	 * @param {Number} index The index of the fragment that
  	 * should be shown, -1 means all are invisible
  	 * @param {Number} offset Integer offset to apply to the
  	 * fragment index
  	 *
  	 * @return {Boolean} true if a change was made in any
  	 * fragments visibility as part of this call
  	 */
  	function navigateFragment( index, offset ) {
  
  		if( currentSlide && config.fragments ) {
  
  			var fragments = sortFragments( currentSlide.querySelectorAll( '.fragment' ) );
  			if( fragments.length ) {
  
  				// If no index is specified, find the current
  				if( typeof index !== 'number' ) {
  					var lastVisibleFragment = sortFragments( currentSlide.querySelectorAll( '.fragment.visible' ) ).pop();
  
  					if( lastVisibleFragment ) {
  						index = parseInt( lastVisibleFragment.getAttribute( 'data-fragment-index' ) || 0, 10 );
  					}
  					else {
  						index = -1;
  					}
  				}
  
  				// If an offset is specified, apply it to the index
  				if( typeof offset === 'number' ) {
  					index += offset;
  				}
  
  				var fragmentsShown = [],
  					fragmentsHidden = [];
  
  				toArray( fragments ).forEach( function( element, i ) {
  
  					if( element.hasAttribute( 'data-fragment-index' ) ) {
  						i = parseInt( element.getAttribute( 'data-fragment-index' ), 10 );
  					}
  
  					// Visible fragments
  					if( i <= index ) {
  						if( !element.classList.contains( 'visible' ) ) fragmentsShown.push( element );
  						element.classList.add( 'visible' );
  						element.classList.remove( 'current-fragment' );
  
  						if( i === index ) {
  							element.classList.add( 'current-fragment' );
  						}
  					}
  					// Hidden fragments
  					else {
  						if( element.classList.contains( 'visible' ) ) fragmentsHidden.push( element );
  						element.classList.remove( 'visible' );
  						element.classList.remove( 'current-fragment' );
  					}
  
  
  				} );
  
  				if( fragmentsHidden.length ) {
  					dispatchEvent( 'fragmenthidden', { fragment: fragmentsHidden[0], fragments: fragmentsHidden } );
  				}
  
  				if( fragmentsShown.length ) {
  					dispatchEvent( 'fragmentshown', { fragment: fragmentsShown[0], fragments: fragmentsShown } );
  				}
  
  				updateControls();
  
  				return !!( fragmentsShown.length || fragmentsHidden.length );
  
  			}
  
  		}
  
  		return false;
  
  	}
  
  	/**
  	 * Navigate to the next slide fragment.
  	 *
  	 * @return {Boolean} true if there was a next fragment,
  	 * false otherwise
  	 */
  	function nextFragment() {
  
  		return navigateFragment( null, 1 );
  
  	}
  
  	/**
  	 * Navigate to the previous slide fragment.
  	 *
  	 * @return {Boolean} true if there was a previous fragment,
  	 * false otherwise
  	 */
  	function previousFragment() {
  
  		return navigateFragment( null, -1 );
  
  	}
  
  	/**
  	 * Cues a new automated slide if enabled in the config.
  	 */
  	function cueAutoSlide() {
  
  		cancelAutoSlide();
  
  		if( currentSlide ) {
  
  			var parentAutoSlide = currentSlide.parentNode ? currentSlide.parentNode.getAttribute( 'data-autoslide' ) : null;
  			var slideAutoSlide = currentSlide.getAttribute( 'data-autoslide' );
  
  			// Pick value in the following priority order:
  			// 1. Current slide's data-autoslide
  			// 2. Parent slide's data-autoslide
  			// 3. Global autoSlide setting
  			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
  			toArray( currentSlide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
  				if( el.hasAttribute( 'data-autoplay' ) ) {
  					if( autoSlide && el.duration * 1000 > autoSlide ) {
  						autoSlide = ( el.duration * 1000 ) + 1000;
  					}
  				}
  			} );
  
  			// Cue the next auto-slide if:
  			// - There is an autoSlide value
  			// - Auto-sliding isn't paused by the user
  			// - The presentation isn't paused
  			// - The overview isn't active
  			// - The presentation isn't over
  			if( autoSlide && !autoSlidePaused && !isPaused() && !isOverview() && ( !Reveal.isLastSlide() || config.loop === true ) ) {
  				autoSlideTimeout = setTimeout( navigateNext, autoSlide );
  				autoSlideStartTime = Date.now();
  			}
  
  			if( autoSlidePlayer ) {
  				autoSlidePlayer.setPlaying( autoSlideTimeout !== -1 );
  			}
  
  		}
  
  	}
  
  	/**
  	 * Cancels any ongoing request to auto-slide.
  	 */
  	function cancelAutoSlide() {
  
  		clearTimeout( autoSlideTimeout );
  		autoSlideTimeout = -1;
  
  	}
  
  	function pauseAutoSlide() {
  
  		autoSlidePaused = true;
  		clearTimeout( autoSlideTimeout );
  
  		if( autoSlidePlayer ) {
  			autoSlidePlayer.setPlaying( false );
  		}
  
  	}
  
  	function resumeAutoSlide() {
  
  		autoSlidePaused = false;
  		cueAutoSlide();
  
  	}
  
  	function navigateLeft() {
  
  		// Reverse for RTL
  		if( config.rtl ) {
  			if( ( isOverview() || nextFragment() === false ) && availableRoutes().left ) {
  				slide( indexh + 1 );
  			}
  		}
  		// Normal navigation
  		else if( ( isOverview() || previousFragment() === false ) && availableRoutes().left ) {
  			slide( indexh - 1 );
  		}
  
  	}
  
  	function navigateRight() {
  
  		// Reverse for RTL
  		if( config.rtl ) {
  			if( ( isOverview() || previousFragment() === false ) && availableRoutes().right ) {
  				slide( indexh - 1 );
  			}
  		}
  		// Normal navigation
  		else if( ( isOverview() || nextFragment() === false ) && availableRoutes().right ) {
  			slide( indexh + 1 );
  		}
  
  	}
  
  	function navigateUp() {
  
  		// Prioritize hiding fragments
  		if( ( isOverview() || previousFragment() === false ) && availableRoutes().up ) {
  			slide( indexh, indexv - 1 );
  		}
  
  	}
  
  	function navigateDown() {
  
  		// Prioritize revealing fragments
  		if( ( isOverview() || nextFragment() === false ) && availableRoutes().down ) {
  			slide( indexh, indexv + 1 );
  		}
  
  	}
  
  	/**
  	 * Navigates backwards, prioritized in the following order:
  	 * 1) Previous fragment
  	 * 2) Previous vertical slide
  	 * 3) Previous horizontal slide
  	 */
  	function navigatePrev() {
  
  		// Prioritize revealing fragments
  		if( previousFragment() === false ) {
  			if( availableRoutes().up ) {
  				navigateUp();
  			}
  			else {
  				// Fetch the previous horizontal slide, if there is one
  				var previousSlide = document.querySelector( HORIZONTAL_SLIDES_SELECTOR + '.past:nth-child(' + indexh + ')' );
  
  				if( previousSlide ) {
  					var v = ( previousSlide.querySelectorAll( 'section' ).length - 1 ) || undefined;
  					var h = indexh - 1;
  					slide( h, v );
  				}
  			}
  		}
  
  	}
  
  	/**
  	 * Same as #navigatePrev() but navigates forwards.
  	 */
  	function navigateNext() {
  
  		// Prioritize revealing fragments
  		if( nextFragment() === false ) {
  			availableRoutes().down ? navigateDown() : navigateRight();
  		}
  
  		// If auto-sliding is enabled we need to cue up
  		// another timeout
  		cueAutoSlide();
  
  	}
  
  
  	// --------------------------------------------------------------------//
  	// ----------------------------- EVENTS -------------------------------//
  	// --------------------------------------------------------------------//
  
  	/**
  	 * Called by all event handlers that are based on user
  	 * input.
  	 */
  	function onUserInput( event ) {
  
  		if( config.autoSlideStoppable ) {
  			pauseAutoSlide();
  		}
  
  	}
  
  	/**
  	 * Handler for the document level 'keydown' event.
  	 */
  	function onDocumentKeyDown( event ) {
  
  		onUserInput( event );
  
  		// Check if there's a focused element that could be using
  		// the keyboard
  		var activeElement = document.activeElement;
  		var hasFocus = !!( document.activeElement && ( document.activeElement.type || document.activeElement.href || document.activeElement.contentEditable !== 'inherit' ) );
  
  		// Disregard the event if there's a focused element or a
  		// keyboard modifier key is present
  		if( hasFocus || (event.shiftKey && event.keyCode !== 32) || event.altKey || event.ctrlKey || event.metaKey ) return;
  
  		// While paused only allow "unpausing" keyboard events (b and .)
  		if( isPaused() && [66,190,191].indexOf( event.keyCode ) === -1 ) {
  			return false;
  		}
  
  		var triggered = false;
  
  		// 1. User defined key bindings
  		if( typeof config.keyboard === 'object' ) {
  
  			for( var key in config.keyboard ) {
  
  				// Check if this binding matches the pressed key
  				if( parseInt( key, 10 ) === event.keyCode ) {
  
  					var value = config.keyboard[ key ];
  
  					// Callback function
  					if( typeof value === 'function' ) {
  						value.apply( null, [ event ] );
  					}
  					// String shortcuts to reveal.js API
  					else if( typeof value === 'string' && typeof Reveal[ value ] === 'function' ) {
  						Reveal[ value ].call();
  					}
  
  					triggered = true;
  
  				}
  
  			}
  
  		}
  
  		// 2. System defined key bindings
  		if( triggered === false ) {
  
  			// Assume true and try to prove false
  			triggered = true;
  
  			switch( event.keyCode ) {
  				// p, page up
  				case 80: case 33: navigatePrev(); break;
  				// n, page down
  				case 78: case 34: navigateNext(); break;
  				// h, left
  				case 72: case 37: navigateLeft(); break;
  				// l, right
  				case 76: case 39: navigateRight(); break;
  				// k, up
  				case 75: case 38: navigateUp(); break;
  				// j, down
  				case 74: case 40: navigateDown(); break;
  				// home
  				case 36: slide( 0 ); break;
  				// end
  				case 35: slide( Number.MAX_VALUE ); break;
  				// space
  				case 32: isOverview() ? deactivateOverview() : event.shiftKey ? navigatePrev() : navigateNext(); break;
  				// return
  				case 13: isOverview() ? deactivateOverview() : triggered = false; break;
  				// b, period, Logitech presenter tools "black screen" button
  				case 66: case 190: case 191: togglePause(); break;
  				// f
  				case 70: enterFullscreen(); break;
  				default:
  					triggered = false;
  			}
  
  		}
  
  		// If the input resulted in a triggered action we should prevent
  		// the browsers default behavior
  		if( triggered ) {
  			event.preventDefault();
  		}
  		// ESC or O key
  		else if ( ( event.keyCode === 27 || event.keyCode === 79 ) && features.transforms3d ) {
  			if( dom.preview ) {
  				closePreview();
  			}
  			else {
  				toggleOverview();
  			}
  
  			event.preventDefault();
  		}
  
  		// If auto-sliding is enabled we need to cue up
  		// another timeout
  		cueAutoSlide();
  
  	}
  
  	/**
  	 * Handler for the 'touchstart' event, enables support for
  	 * swipe and pinch gestures.
  	 */
  	function onTouchStart( event ) {
  
  		touch.startX = event.touches[0].clientX;
  		touch.startY = event.touches[0].clientY;
  		touch.startCount = event.touches.length;
  
  		// If there's two touches we need to memorize the distance
  		// between those two points to detect pinching
  		if( event.touches.length === 2 && config.overview ) {
  			touch.startSpan = distanceBetween( {
  				x: event.touches[1].clientX,
  				y: event.touches[1].clientY
  			}, {
  				x: touch.startX,
  				y: touch.startY
  			} );
  		}
  
  	}
  
  	/**
  	 * Handler for the 'touchmove' event.
  	 */
  	function onTouchMove( event ) {
  
  		// Each touch should only trigger one action
  		if( !touch.captured ) {
  			onUserInput( event );
  
  			var currentX = event.touches[0].clientX;
  			var currentY = event.touches[0].clientY;
  
  			// If the touch started with two points and still has
  			// two active touches; test for the pinch gesture
  			if( event.touches.length === 2 && touch.startCount === 2 && config.overview ) {
  
  				// The current distance in pixels between the two touch points
  				var currentSpan = distanceBetween( {
  					x: event.touches[1].clientX,
  					y: event.touches[1].clientY
  				}, {
  					x: touch.startX,
  					y: touch.startY
  				} );
  
  				// If the span is larger than the desire amount we've got
  				// ourselves a pinch
  				if( Math.abs( touch.startSpan - currentSpan ) > touch.threshold ) {
  					touch.captured = true;
  
  					if( currentSpan < touch.startSpan ) {
  						activateOverview();
  					}
  					else {
  						deactivateOverview();
  					}
  				}
  
  				event.preventDefault();
  
  			}
  			// There was only one touch point, look for a swipe
  			else if( event.touches.length === 1 && touch.startCount !== 2 ) {
  
  				var deltaX = currentX - touch.startX,
  					deltaY = currentY - touch.startY;
  
  				if( deltaX > touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
  					touch.captured = true;
  					navigateLeft();
  				}
  				else if( deltaX < -touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
  					touch.captured = true;
  					navigateRight();
  				}
  				else if( deltaY > touch.threshold ) {
  					touch.captured = true;
  					navigateUp();
  				}
  				else if( deltaY < -touch.threshold ) {
  					touch.captured = true;
  					navigateDown();
  				}
  
  				// If we're embedded, only block touch events if they have
  				// triggered an action
  				if( config.embedded ) {
  					if( touch.captured || isVerticalSlide( currentSlide ) ) {
  						event.preventDefault();
  					}
  				}
  				// Not embedded? Block them all to avoid needless tossing
  				// around of the viewport in iOS
  				else {
  					event.preventDefault();
  				}
  
  			}
  		}
  		// There's a bug with swiping on some Android devices unless
  		// the default action is always prevented
  		else if( navigator.userAgent.match( /android/gi ) ) {
  			event.preventDefault();
  		}
  
  	}
  
  	/**
  	 * Handler for the 'touchend' event.
  	 */
  	function onTouchEnd( event ) {
  
  		touch.captured = false;
  
  	}
  
  	/**
  	 * Convert pointer down to touch start.
  	 */
  	function onPointerDown( event ) {
  
  		if( event.pointerType === event.MSPOINTER_TYPE_TOUCH ) {
  			event.touches = [{ clientX: event.clientX, clientY: event.clientY }];
  			onTouchStart( event );
  		}
  
  	}
  
  	/**
  	 * Convert pointer move to touch move.
  	 */
  	function onPointerMove( event ) {
  
  		if( event.pointerType === event.MSPOINTER_TYPE_TOUCH ) {
  			event.touches = [{ clientX: event.clientX, clientY: event.clientY }];
  			onTouchMove( event );
  		}
  
  	}
  
  	/**
  	 * Convert pointer up to touch end.
  	 */
  	function onPointerUp( event ) {
  
  		if( event.pointerType === event.MSPOINTER_TYPE_TOUCH ) {
  			event.touches = [{ clientX: event.clientX, clientY: event.clientY }];
  			onTouchEnd( event );
  		}
  
  	}
  
  	/**
  	 * Handles mouse wheel scrolling, throttled to avoid skipping
  	 * multiple slides.
  	 */
  	function onDocumentMouseScroll( event ) {
  
  		if( Date.now() - lastMouseWheelStep > 600 ) {
  
  			lastMouseWheelStep = Date.now();
  
  			var delta = event.detail || -event.wheelDelta;
  			if( delta > 0 ) {
  				navigateNext();
  			}
  			else {
  				navigatePrev();
  			}
  
  		}
  
  	}
  
  	/**
  	 * Clicking on the progress bar results in a navigation to the
  	 * closest approximate horizontal slide using this equation:
  	 *
  	 * ( clickX / presentationWidth ) * numberOfSlides
  	 */
  	function onProgressClicked( event ) {
  
  		onUserInput( event );
  
  		event.preventDefault();
  
  		var slidesTotal = toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).length;
  		var slideIndex = Math.floor( ( event.clientX / dom.wrapper.offsetWidth ) * slidesTotal );
  
  		slide( slideIndex );
  
  	}
  
  	/**
  	 * Event handler for navigation control buttons.
  	 */
  	function onNavigateLeftClicked( event ) { event.preventDefault(); onUserInput(); navigateLeft(); }
  	function onNavigateRightClicked( event ) { event.preventDefault(); onUserInput(); navigateRight(); }
  	function onNavigateUpClicked( event ) { event.preventDefault(); onUserInput(); navigateUp(); }
  	function onNavigateDownClicked( event ) { event.preventDefault(); onUserInput(); navigateDown(); }
  	function onNavigatePrevClicked( event ) { event.preventDefault(); onUserInput(); navigatePrev(); }
  	function onNavigateNextClicked( event ) { event.preventDefault(); onUserInput(); navigateNext(); }
  
  	/**
  	 * Handler for the window level 'hashchange' event.
  	 */
  	function onWindowHashChange( event ) {
  
  		readURL();
  
  	}
  
  	/**
  	 * Handler for the window level 'resize' event.
  	 */
  	function onWindowResize( event ) {
  
  		layout();
  
  	}
  
  	/**
  	 * Handle for the window level 'visibilitychange' event.
  	 */
  	function onPageVisibilityChange( event ) {
  
  		var isHidden =  document.webkitHidden ||
  						document.msHidden ||
  						document.hidden;
  
  		// If, after clicking a link or similar and we're coming back,
  		// focus the document.body to ensure we can use keyboard shortcuts
  		if( isHidden === false && document.activeElement !== document.body ) {
  			document.activeElement.blur();
  			document.body.focus();
  		}
  
  	}
  
  	/**
  	 * Invoked when a slide is and we're in the overview.
  	 */
  	function onOverviewSlideClicked( event ) {
  
  		// TODO There's a bug here where the event listeners are not
  		// removed after deactivating the overview.
  		if( eventsAreBound && isOverview() ) {
  			event.preventDefault();
  
  			var element = event.target;
  
  			while( element && !element.nodeName.match( /section/gi ) ) {
  				element = element.parentNode;
  			}
  
  			if( element && !element.classList.contains( 'disabled' ) ) {
  
  				deactivateOverview();
  
  				if( element.nodeName.match( /section/gi ) ) {
  					var h = parseInt( element.getAttribute( 'data-index-h' ), 10 ),
  						v = parseInt( element.getAttribute( 'data-index-v' ), 10 );
  
  					slide( h, v );
  				}
  
  			}
  		}
  
  	}
  
  	/**
  	 * Handles clicks on links that are set to preview in the
  	 * iframe overlay.
  	 */
  	function onPreviewLinkClicked( event ) {
  
  		var url = event.target.getAttribute( 'href' );
  		if( url ) {
  			openPreview( url );
  			event.preventDefault();
  		}
  
  	}
  
  	/**
  	 * Handles click on the auto-sliding controls element.
  	 */
  	function onAutoSlidePlayerClick( event ) {
  
  		// Replay
  		if( Reveal.isLastSlide() && config.loop === false ) {
  			slide( 0, 0 );
  			resumeAutoSlide();
  		}
  		// Resume
  		else if( autoSlidePaused ) {
  			resumeAutoSlide();
  		}
  		// Pause
  		else {
  			pauseAutoSlide();
  		}
  
  	}
  
  
  	// --------------------------------------------------------------------//
  	// ------------------------ PLAYBACK COMPONENT ------------------------//
  	// --------------------------------------------------------------------//
  
  
  	/**
  	 * Constructor for the playback component, which displays
  	 * play/pause/progress controls.
  	 *
  	 * @param {HTMLElement} container The component will append
  	 * itself to this
  	 * @param {Function} progressCheck A method which will be
  	 * called frequently to get the current progress on a range
  	 * of 0-1
  	 */
  	function Playback( container, progressCheck ) {
  
  		// Cosmetics
  		this.diameter = 50;
  		this.thickness = 3;
  
  		// Flags if we are currently playing
  		this.playing = false;
  
  		// Current progress on a 0-1 range
  		this.progress = 0;
  
  		// Used to loop the animation smoothly
  		this.progressOffset = 1;
  
  		this.container = container;
  		this.progressCheck = progressCheck;
  
  		this.canvas = document.createElement( 'canvas' );
  		this.canvas.className = 'playback';
  		this.canvas.width = this.diameter;
  		this.canvas.height = this.diameter;
  		this.context = this.canvas.getContext( '2d' );
  
  		this.container.appendChild( this.canvas );
  
  		this.render();
  
  	}
  
  	Playback.prototype.setPlaying = function( value ) {
  
  		var wasPlaying = this.playing;
  
  		this.playing = value;
  
  		// Start repainting if we weren't already
  		if( !wasPlaying && this.playing ) {
  			this.animate();
  		}
  		else {
  			this.render();
  		}
  
  	};
  
  	Playback.prototype.animate = function() {
  
  		var progressBefore = this.progress;
  
  		this.progress = this.progressCheck();
  
  		// When we loop, offset the progress so that it eases
  		// smoothly rather than immediately resetting
  		if( progressBefore > 0.8 && this.progress < 0.2 ) {
  			this.progressOffset = this.progress;
  		}
  
  		this.render();
  
  		if( this.playing ) {
  			features.requestAnimationFrameMethod.call( window, this.animate.bind( this ) );
  		}
  
  	};
  
  	/**
  	 * Renders the current progress and playback state.
  	 */
  	Playback.prototype.render = function() {
  
  		var progress = this.playing ? this.progress : 0,
  			radius = ( this.diameter / 2 ) - this.thickness,
  			x = this.diameter / 2,
  			y = this.diameter / 2,
  			iconSize = 14;
  
  		// Ease towards 1
  		this.progressOffset += ( 1 - this.progressOffset ) * 0.1;
  
  		var endAngle = ( - Math.PI / 2 ) + ( progress * ( Math.PI * 2 ) );
  		var startAngle = ( - Math.PI / 2 ) + ( this.progressOffset * ( Math.PI * 2 ) );
  
  		this.context.save();
  		this.context.clearRect( 0, 0, this.diameter, this.diameter );
  
  		// Solid background color
  		this.context.beginPath();
  		this.context.arc( x, y, radius + 2, 0, Math.PI * 2, false );
  		this.context.fillStyle = 'rgba( 0, 0, 0, 0.4 )';
  		this.context.fill();
  
  		// Draw progress track
  		this.context.beginPath();
  		this.context.arc( x, y, radius, 0, Math.PI * 2, false );
  		this.context.lineWidth = this.thickness;
  		this.context.strokeStyle = '#666';
  		this.context.stroke();
  
  		if( this.playing ) {
  			// Draw progress on top of track
  			this.context.beginPath();
  			this.context.arc( x, y, radius, startAngle, endAngle, false );
  			this.context.lineWidth = this.thickness;
  			this.context.strokeStyle = '#fff';
  			this.context.stroke();
  		}
  
  		this.context.translate( x - ( iconSize / 2 ), y - ( iconSize / 2 ) );
  
  		// Draw play/pause icons
  		if( this.playing ) {
  			this.context.fillStyle = '#fff';
  			this.context.fillRect( 0, 0, iconSize / 2 - 2, iconSize );
  			this.context.fillRect( iconSize / 2 + 2, 0, iconSize / 2 - 2, iconSize );
  		}
  		else {
  			this.context.beginPath();
  			this.context.translate( 2, 0 );
  			this.context.moveTo( 0, 0 );
  			this.context.lineTo( iconSize - 2, iconSize / 2 );
  			this.context.lineTo( 0, iconSize );
  			this.context.fillStyle = '#fff';
  			this.context.fill();
  		}
  
  		this.context.restore();
  
  	};
  
  	Playback.prototype.on = function( type, listener ) {
  		this.canvas.addEventListener( type, listener, false );
  	};
  
  	Playback.prototype.off = function( type, listener ) {
  		this.canvas.removeEventListener( type, listener, false );
  	};
  
  	Playback.prototype.destroy = function() {
  
  		this.playing = false;
  
  		if( this.canvas.parentNode ) {
  			this.container.removeChild( this.canvas );
  		}
  
  	};
  
  
  	// --------------------------------------------------------------------//
  	// ------------------------------- API --------------------------------//
  	// --------------------------------------------------------------------//
  
  
  	return {
  		initialize: initialize,
  		configure: configure,
  		sync: sync,
  
  		// Navigation methods
  		slide: slide,
  		left: navigateLeft,
  		right: navigateRight,
  		up: navigateUp,
  		down: navigateDown,
  		prev: navigatePrev,
  		next: navigateNext,
  
  		// Fragment methods
  		navigateFragment: navigateFragment,
  		prevFragment: previousFragment,
  		nextFragment: nextFragment,
  
  		// Deprecated aliases
  		navigateTo: slide,
  		navigateLeft: navigateLeft,
  		navigateRight: navigateRight,
  		navigateUp: navigateUp,
  		navigateDown: navigateDown,
  		navigatePrev: navigatePrev,
  		navigateNext: navigateNext,
  
  		// Forces an update in slide layout
  		layout: layout,
  
  		// Returns an object with the available routes as booleans (left/right/top/bottom)
  		availableRoutes: availableRoutes,
  
  		// Returns an object with the available fragments as booleans (prev/next)
  		availableFragments: availableFragments,
  
  		// Toggles the overview mode on/off
  		toggleOverview: toggleOverview,
  
  		// Toggles the "black screen" mode on/off
  		togglePause: togglePause,
  
  		// State checks
  		isOverview: isOverview,
  		isPaused: isPaused,
  
  		// Adds or removes all internal event listeners (such as keyboard)
  		addEventListeners: addEventListeners,
  		removeEventListeners: removeEventListeners,
  
  		// Returns the indices of the current, or specified, slide
  		getIndices: getIndices,
  
  		// Returns the slide at the specified index, y is optional
  		getSlide: function( x, y ) {
  			var horizontalSlide = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR )[ x ];
  			var verticalSlides = horizontalSlide && horizontalSlide.querySelectorAll( 'section' );
  
  			if( typeof y !== 'undefined' ) {
  				return verticalSlides ? verticalSlides[ y ] : undefined;
  			}
  
  			return horizontalSlide;
  		},
  
  		// Returns the previous slide element, may be null
  		getPreviousSlide: function() {
  			return previousSlide;
  		},
  
  		// Returns the current slide element
  		getCurrentSlide: function() {
  			return currentSlide;
  		},
  
  		// Returns the current scale of the presentation content
  		getScale: function() {
  			return scale;
  		},
  
  		// Returns the current configuration object
  		getConfig: function() {
  			return config;
  		},
  
  		// Helper method, retrieves query string as a key/value hash
  		getQueryHash: function() {
  			var query = {};
  
  			location.search.replace( /[A-Z0-9]+?=([\w\.%-]*)/gi, function(a) {
  				query[ a.split( '=' ).shift() ] = a.split( '=' ).pop();
  			} );
  
  			// Basic deserialization
  			for( var i in query ) {
  				var value = query[ i ];
  
  				query[ i ] = unescape( value );
  
  				if( value === 'null' ) query[ i ] = null;
  				else if( value === 'true' ) query[ i ] = true;
  				else if( value === 'false' ) query[ i ] = false;
  				else if( value.match( /^\d+$/ ) ) query[ i ] = parseFloat( value );
  			}
  
  			return query;
  		},
  
  		// Returns true if we're currently on the first slide
  		isFirstSlide: function() {
  			return document.querySelector( SLIDES_SELECTOR + '.past' ) == null ? true : false;
  		},
  
  		// Returns true if we're currently on the last slide
  		isLastSlide: function() {
  			if( currentSlide ) {
  				// Does this slide has next a sibling?
  				if( currentSlide.nextElementSibling ) return false;
  
  				// If it's vertical, does its parent have a next sibling?
  				if( isVerticalSlide( currentSlide ) && currentSlide.parentNode.nextElementSibling ) return false;
  
  				return true;
  			}
  
  			return false;
  		},
  
  		// Checks if reveal.js has been loaded and is ready for use
  		isReady: function() {
  			return loaded;
  		},
  
  		// Forward event binding to the reveal DOM element
  		addEventListener: function( type, listener, useCapture ) {
  			if( 'addEventListener' in window ) {
  				( dom.wrapper || document.querySelector( '.reveal' ) ).addEventListener( type, listener, useCapture );
  			}
  		},
  		removeEventListener: function( type, listener, useCapture ) {
  			if( 'addEventListener' in window ) {
  				( dom.wrapper || document.querySelector( '.reveal' ) ).removeEventListener( type, listener, useCapture );
  			}
  		}
  	};
  
  })();
  