reveal.js

		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 );

	}

	/**
	 * Utility for deserializing a value.
	 */
	function deserialize( value ) {

		if( typeof value === 'string' ) {
			if( value === 'null' ) return null;
			else if( value === 'true' ) return true;
			else if( value === 'false' ) return false;
			else if( value.match( /^\d+$/ ) ) return parseFloat( value );
		}

		return value;

	}

	/**
	 * Measures the distance in pixels between point a
	 * and point b.
	 *
	 * @param {Object} a point with x/y properties
	 * @param {Object} b point with x/y properties
	 */
	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.transform = transform;

	}

	/**
	 * Injects the given CSS styles into the DOM.
	 */
	function injectStyleSheet( value ) {

		var tag = document.createElement( 'style' );
		tag.type = 'text/css';
		if( tag.styleSheet ) {
			tag.styleSheet.cssText = value;
		}
		else {
			tag.appendChild( document.createTextNode( value ) );
		}
		document.getElementsByTagName( 'head' )[0].appendChild( tag );

	}

	/**
	 * Measures the distance in pixels between point a and point b.
	 *
	 * @param {String} color The string representation of a color,
	 * the following formats are supported:
	 * - #000
	 * - #000000
	 * - rgb(0,0,0)
	 */
	function colorToRgb( color ) {

		var hex3 = color.match( /^#([0-9a-f]{3})$/i );
		if( hex3 && hex3[1] ) {
			hex3 = hex3[1];
			return {
				r: parseInt( hex3.charAt( 0 ), 16 ) * 0x11,
				g: parseInt( hex3.charAt( 1 ), 16 ) * 0x11,
				b: parseInt( hex3.charAt( 2 ), 16 ) * 0x11
			};
		}

		var hex6 = color.match( /^#([0-9a-f]{6})$/i );
		if( hex6 && hex6[1] ) {
			hex6 = hex6[1];
			return {
				r: parseInt( hex6.substr( 0, 2 ), 16 ),
				g: parseInt( hex6.substr( 2, 2 ), 16 ),
				b: parseInt( hex6.substr( 4, 2 ), 16 )
			};
		}

		var rgb = color.match( /^rgb\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)$/i );
		if( rgb ) {
			return {
				r: parseInt( rgb[1], 10 ),
				g: parseInt( rgb[2], 10 ),
				b: parseInt( rgb[3], 10 )
			};
		}

		var rgba = color.match( /^rgba\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\,\s*([\d]+|[\d]*.[\d]+)\s*\)$/i );
		if( rgba ) {
			return {
				r: parseInt( rgba[1], 10 ),
				g: parseInt( rgba[2], 10 ),
				b: parseInt( rgba[3], 10 ),
				a: parseFloat( rgba[4] )
			};
		}

		return null;

	}

	/**
	 * Calculates brightness on a scale of 0-255.
	 *
	 * @param color See colorStringToRgb for supported formats.
	 */
	function colorBrightness( color ) {

		if( typeof color === 'string' ) color = colorToRgb( color );

		if( color ) {
			return ( color.r * 299 + color.g * 587 + color.b * 114 ) / 1000;
		}

		return null;

	}

	/**
	 * 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( window.getComputedStyle( child ).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.
	 *
	 * remaining height = [ configured parent height ] - [ current parent height ]
	 */
	function getRemainingHeight( element, height ) {

		height = height || 0;

		if( element ) {
			var newHeight, oldHeight = element.style.height;

			// Change the .stretch element height to 0 in order find the height of all
			// the other elements
			element.style.height = '0px';
			newHeight = height - element.parentNode.offsetHeight;

			// Restore the old height, just in case
			element.style.height = oldHeight + 'px';

			return newHeight;
		}

		return height;

	}

	/**
	 * Checks if this instance is being used to print a PDF.
	 */
	function isPrintingPDF() {

		return ( /print-pdf/gi ).test( window.location.search );

	}

	/**
	 * Hides the address bar if we're on a mobile device.
	 */
	function hideAddressBar() {

		if( config.hideAddressBar && isMobileDevice ) {
			// Events that should trigger the address bar to hide
			window.addEventListener( 'load', removeAddressBar, false );
			window.addEventListener( 'orientationchange', removeAddressBar, false );
		}

	}

	/**
	 * Causes the address bar to hide on mobile devices,
	 * more vertical space ftw.
	 */
	function removeAddressBar() {

		setTimeout( function() {
			window.scrollTo( 0, 1 );
		}, 10 );

	}

	/**
	 * Dispatches an event of the specified type from the
	 * reveal DOM element.
	 */
	function dispatchEvent( type, args ) {

		var event = document.createEvent( 'HTMLEvents', 1, 2 );
		event.initEvent( type, true, true );
		extend( event, args );
		dom.wrapper.dispatchEvent( event );

		// If we're in an iframe, post each reveal.js event to the
		// parent window. Used by the notes plugin
		if( config.postMessageEvents && window.parent !== window.self ) {
			window.parent.postMessage( JSON.stringify({ namespace: 'reveal', eventName: type, state: getState() }), '*' );
		}

	}

	/**
	 * Wrap all links in 3D goodness.
	 */
	function enableRollingLinks() {

		if( features.transforms3d && !( 'msPerspective' in document.body.style ) ) {
			var anchors = dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' a' );

			for( var i = 0, len = anchors.length; i < len; i++ ) {
				var anchor = anchors[i];

				if( anchor.textContent && !anchor.querySelector( '*' ) && ( !anchor.className || !anchor.classList.contains( anchor, 'roll' ) ) ) {
					var span = document.createElement('span');
					span.setAttribute('data-title', anchor.text);
					span.innerHTML = anchor.innerHTML;

					anchor.classList.add( 'roll' );
					anchor.innerHTML = '';
					anchor.appendChild(span);
				}
			}
		}

	}

	/**
	 * Unwrap all 3D links.
	 */
	function disableRollingLinks() {

		var anchors = dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' a.roll' );

		for( var i = 0, len = anchors.length; i < len; i++ ) {
			var anchor = anchors[i];
			var span = anchor.querySelector( 'span' );

			if( span ) {
				anchor.classList.remove( 'roll' );
				anchor.innerHTML = span.innerHTML;
			}
		}

	}

	/**
	 * Bind preview frame links.
	 */
	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 showPreview( url ) {

		closeOverlay();

		dom.overlay = document.createElement( 'div' );
		dom.overlay.classList.add( 'overlay' );
		dom.overlay.classList.add( 'overlay-preview' );
		dom.wrapper.appendChild( dom.overlay );

		dom.overlay.innerHTML = [
			'<header>',
				'<a class="close" href="#"><span class="icon"></span></a>',
				'<a class="external" href="'+ url +'" target="_blank"><span class="icon"></span></a>',
			'</header>',
			'<div class="spinner"></div>',
			'<div class="viewport">',
				'<iframe src="'+ url +'"></iframe>',
			'</div>'
		].join('');

		dom.overlay.querySelector( 'iframe' ).addEventListener( 'load', function( event ) {
			dom.overlay.classList.add( 'loaded' );
		}, false );

		dom.overlay.querySelector( '.close' ).addEventListener( 'click', function( event ) {
			closeOverlay();
			event.preventDefault();
		}, false );

		dom.overlay.querySelector( '.external' ).addEventListener( 'click', function( event ) {
			closeOverlay();
		}, false );

		setTimeout( function() {
			dom.overlay.classList.add( 'visible' );
		}, 1 );

	}

	/**
	 * Opens a overlay window with help material.
	 */
	function showHelp() {

		if( config.help ) {

			closeOverlay();

			dom.overlay = document.createElement( 'div' );
			dom.overlay.classList.add( 'overlay' );
			dom.overlay.classList.add( 'overlay-help' );
			dom.wrapper.appendChild( dom.overlay );

			var html = '<p class="title">Keyboard Shortcuts</p><br/>';

			html += '<table><th>KEY</th><th>ACTION</th>';
			for( var key in keyboardShortcuts ) {
				html += '<tr><td>' + key + '</td><td>' + keyboardShortcuts[ key ] + '</td></tr>';
			}

			html += '</table>';

			dom.overlay.innerHTML = [
				'<header>',
					'<a class="close" href="#"><span class="icon"></span></a>',
				'</header>',
				'<div class="viewport">',
					'<div class="viewport-inner">'+ html +'</div>',
				'</div>'
			].join('');

			dom.overlay.querySelector( '.close' ).addEventListener( 'click', function( event ) {
				closeOverlay();
				event.preventDefault();
			}, false );

			setTimeout( function() {
				dom.overlay.classList.add( 'visible' );
			}, 1 );

		}

	}

	/**
	 * Closes any currently open overlay.
	 */
	function closeOverlay() {

		if( dom.overlay ) {
			dom.overlay.parentNode.removeChild( dom.overlay );
			dom.overlay = null;
		}

	}

	/**
	 * Applies JavaScript-controlled layout rules to the
	 * presentation.
	 */
	function layout() {

		if( dom.wrapper && !isPrintingPDF() ) {

			var size = getComputedSlideSize();

			var slidePadding = 20; // TODO Dig this out of DOM
			var zTransform = z !== 0 ? 'translateZ(-'+ z +'px)' : '';

			// Layout the contents of the slides
			layoutSlideContents( config.width, config.height, slidePadding );

			dom.slides.style.width = size.width + 'px';
			dom.slides.style.height = size.height + 'px';

			// Determine scale of content to fit within available space
			scale = Math.min( size.presentationWidth / size.width, size.presentationHeight / size.height );

			// Respect max/min scale settings
			scale = Math.max( scale, config.minScale );
			scale = Math.min( scale, config.maxScale );

			// Don't apply any scaling styles if scale is 1
			if( scale === 1 ) {
				dom.slides.style.zoom = '';
				dom.slides.style.left = '';
				dom.slides.style.top = '';
				dom.slides.style.bottom = '';
				dom.slides.style.right = '';
				transformElement( dom.slides, zTransform );
			}
			else {
				// Prefer zooming in desktop Chrome so that content remains crisp
				if( !isMobileDevice && /chrome/i.test( navigator.userAgent ) && typeof dom.slides.style.zoom !== 'undefined' ) {
					dom.slides.style.zoom = scale;
					transformElement( dom.slides, zTransform );
				}
				// Apply scale transform as a fallback
				else {
					dom.slides.style.left = '50%';
					dom.slides.style.top = '50%';
					dom.slides.style.bottom = 'auto';
					dom.slides.style.right = 'auto';
					transformElement( dom.slides, 'translate(-50%, -50%) scale('+ scale +') ' + zTransform );
				}
			}

			// Select all slides, vertical and horizontal
			var slides = toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) );

			for( var i = 0, len = slides.length; i < len; i++ ) {
				var slide = slides[ i ];

				// Don't bother updating invisible slides
				if( slide.style.display === 'none' ) {
					continue;
				}

				if( config.center || slide.classList.contains( 'center' ) ) {
					// Vertical stacks are not centred since their section
					// children will be
					if( slide.classList.contains( 'stack' ) ) {
						slide.style.top = 0;
					}
					else {
						slide.style.top = Math.max( ( ( size.height - getAbsoluteHeight( slide ) ) / 2 ) - slidePadding, 0 ) + '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 );

			// Consider the aspect ratio of media elements
			if( /(img|video)/gi.test( element.nodeName ) ) {
				var nw = element.naturalWidth || element.videoWidth,
					nh = element.naturalHeight || element.videoHeight;

				var es = Math.min( width / nw, remainingHeight / nh );

				element.style.width = ( nw * es ) + 'px';
				element.style.height = ( nh * es ) + 'px';

			}
			else {
				element.style.width = width + 'px';
				element.style.height = remainingHeight + 'px';
			}

		} );

	}

	/**
	 * Calculates the computed pixel size of our slides. These
	 * values are based on the width and height configuration
	 * options.
	 */
	function getComputedSlideSize( presentationWidth, presentationHeight ) {

		var size = {
			// Slide size
			width: config.width,
			height: config.height,

			// Presentation size
			presentationWidth: presentationWidth || dom.wrapper.offsetWidth,
			presentationHeight: presentationHeight || dom.wrapper.offsetHeight
		};

		// Reduce available space by margin
		size.presentationWidth -= ( size.presentationHeight * config.margin );
		size.presentationHeight -= ( size.presentationHeight * config.margin );

		// Slide width may be a percentage of available width
		if( typeof size.width === 'string' && /%$/.test( size.width ) ) {
			size.width = parseInt( size.width, 10 ) / 100 * size.presentationWidth;
		}

		// Slide height may be a percentage of available height
		if( typeof size.height === 'string' && /%$/.test( size.height ) ) {
			size.height = parseInt( size.height, 10 ) / 100 * size.presentationHeight;
		}

		return size;

	}

	/**
	 * Stores the vertical index of a stack so that the same
	 * vertical slide can be selected when navigating to and
	 * from the stack.
	 *
	 * @param {HTMLElement} stack The vertical stack element
	 * @param {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' );

			// Set the depth of the presentation. This determinse how far we
			// zoom out and varies based on display size. It gets applied at
			// the layout step.
			z = window.innerWidth < 400 ? 1000 : 2500;

			dom.wrapper.classList.add( 'overview' );
			dom.wrapper.classList.remove( 'overview-deactivating' );

			// Move the backgrounds element into the slide container to
			// that the same scaling is applied
			dom.slides.appendChild( dom.background );

			var horizontalSlides = dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ),
				horizontalBackgrounds = dom.background.childNodes;

			for( var i = 0, len1 = horizontalSlides.length; i < len1; i++ ) {
				var hslide = horizontalSlides[i],
					hbackground = horizontalBackgrounds[i],
					hoffset = config.rtl ? -105 : 105;

				var htransform = 'translate(' + ( ( i - indexh ) * hoffset ) + '%, 0%)';

				hslide.setAttribute( 'data-index-h', i );

				// Apply CSS transform
				transformElement( hslide, htransform );
				transformElement( hbackground, htransform );

				if( hslide.classList.contains( 'stack' ) ) {

					var verticalSlides = hslide.querySelectorAll( 'section' ),
						verticalBackgrounds = hbackground.querySelectorAll( '.slide-background' );

					for( var j = 0, len2 = verticalSlides.length; j < len2; j++ ) {
						var verticalIndex = i === indexh ? indexv : getPreviousVerticalIndex( hslide );

						var vslide = verticalSlides[j],
							vbackground = verticalBackgrounds[j];

						var vtransform = 'translate(0%, ' + ( ( j - verticalIndex ) * 105 ) + '%)';

						vslide.setAttribute( 'data-index-h', i );
						vslide.setAttribute( 'data-index-v', j );

						// Apply CSS transform
						transformElement( vslide, vtransform );
						transformElement( vbackground, vtransform );

						// 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
				} );
			}

		}

	}

	/**
	 * Exits the slide overview and enters the currently
	 * active slide.
	 */
	function deactivateOverview() {

		// Only proceed if enabled in config
		if( config.overview ) {

			dom.wrapper.classList.remove( 'overview' );

			// Move the background element back out
			dom.wrapper.appendChild( dom.background );

			// Temporarily add a class so that transitions can do different things
			// depending on whether they are exiting/entering overview, or just
			// moving from slide to slide
			dom.wrapper.classList.add( 'overview-deactivating' );

			setTimeout( function () {
				dom.wrapper.classList.remove( 'overview-deactivating' );
			}, 1 );

			// Clean up changes made to slides
			toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) ).forEach( function( slide ) {
				transformElement( slide, '' );

				slide.removeEventListener( 'click', onOverviewSlideClicked, true );
			} );

			// Clean up changes made to backgrounds
			toArray( dom.background.querySelectorAll( '.slide-background' ) ).forEach( function( background ) {
				transformElement( background, '' );
			} );

			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() {

		if( config.pause ) {
			var wasPaused = dom.wrapper.classList.contains( 'paused' );

			cancelAutoSlide();
			dom.wrapper.classList.add( 'paused' );

			if( wasPaused === false ) {
				dispatchEvent( 'paused' );
			}
		}

	}

	/**
	 * Exits from the paused mode.
	 */
	function resume() {

		var wasPaused = dom.wrapper.classList.contains( 'paused' );
		dom.wrapper.classList.remove( 'paused' );

		cueAutoSlide();

		if( wasPaused ) {
			dispatchEvent( 'resumed' );
		}

	}

	/**
	 * Toggles the paused mode on and off.
	 */
	function togglePause( override ) {

		if( typeof override === 'boolean' ) {
			override ? pause() : resume();
		}
		else {
			isPaused() ? resume() : pause();
		}

	}

	/**
	 * Checks if we are currently in the paused mode.
	 */
	function isPaused() {

		return dom.wrapper.classList.contains( 'paused' );

	}

	/**
	 * Toggles the auto slide mode on and off.
	 *
	 * @param {Boolean} override Optional flag which sets the desired state.
	 * True means autoplay starts, false means it stops.
	 */

	function toggleAutoSlide( override ) {

		if( typeof override === 'boolean' ) {
			override ? resumeAutoSlide() : pauseAutoSlide();
		}

		else {
			autoSlidePaused ? resumeAutoSlide() : pauseAutoSlide();
		}

	}

	/**
	 * Checks if the auto slide mode is currently on.
	 */
	function isAutoSliding() {

		return !!( autoSlide && !autoSlidePaused );

	}

	/**
	 * Steps from the current point in the presentation to the
	 * slide which matches the specified horizontal and vertical
	 * indices.
	 *
	 * @param {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 = dom.wrapper.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();
		}