reveal.js

			// 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.querySelectorAll( '.slide-background' ) ).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;
					}

				} );
			}

		} );

		// Stop any currently playing video background
		if( previousBackground ) {

			var previousVideo = previousBackground.querySelector( 'video' );
			if( previousVideo ) previousVideo.pause();

		}

		if( currentBackground ) {

			// Start video playback
			var currentVideo = currentBackground.querySelector( 'video' );
			if( currentVideo ) currentVideo.play();

			// Don't transition between identical backgrounds. This
			// prevents unwanted flicker.
			var previousBackgroundHash = previousBackground ? previousBackground.getAttribute( 'data-background-hash' ) : null;
			var currentBackgroundHash = currentBackground.getAttribute( 'data-background-hash' );
			if( currentBackgroundHash && currentBackgroundHash === previousBackgroundHash && currentBackground !== previousBackground ) {
				dom.background.classList.add( 'no-transition' );
			}

			previousBackground = currentBackground;

		}

		// 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 > 1 ? -( 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":""}', '*' );
				}
			});
		}

	}

	/**
	 * Returns a value ranging from 0-1 that represents
	 * how far into the presentation we have navigated.
	 */
	function getProgress() {

		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++;
			}

		}

		if( currentSlide ) {

			var allFragments = currentSlide.querySelectorAll( '.fragment' );

			// If there are fragments in the current slide those should be
			// accounted for in the progress.
			if( allFragments.length > 0 ) {
				var visibleFragments = currentSlide.querySelectorAll( '.fragment.visible' );

				// This value represents how big a portion of the slide progress
				// that is made up by its fragments (0-1)
				var fragmentWeight = 0.9;

				// Add fragment progress to the past slide count
				pastCount += ( visibleFragments.length / allFragments.length ) * fragmentWeight;
			}

		}

		return pastCount / ( totalCount - 1 );

	}

	/**
	 * Checks if this presentation is running inside of the
	 * speaker notes window.
	 */
	function isSpeakerNotes() {

		return !!window.location.search.match( /receiver/gi );

	}

	/**
	 * Reads the current URL (hash) and navigates accordingly.
	 */
	function readURL() {

		var hash = window.location.hash;

		// Attempt to parse the hash as either an index or name
		var bits = hash.slice( 2 ).split( '/' ),
			name = hash.replace( /#|\//gi, '' );

		// If the first bit is invalid and there is a name we can
		// assume that this is a named link
		if( isNaN( parseInt( bits[0], 10 ) ) && name.length ) {
			var element;

			try {
				// Find the slide with the specified name
				element = document.querySelector( '#' + name );
			}
			catch( e ) {
				// If the ID is an invalid selector a harmless SyntaxError
				// may be thrown here.
			}

			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 = '/';

				// Attempt to create a named link based on the slide's ID
				var id = currentSlide.getAttribute( 'id' );
				if( id ) {
					id = id.toLowerCase();
					id = id.replace( /[^a-zA-Z0-9\-\_\:\.]/g, '' );
				}

				// If the current slide has an ID, use that as a named link
				if( currentSlide && typeof id === 'string' && id.length ) {
					url = '/' + id;
				}
				// Otherwise use the /h/v index
				else {
					if( indexh > 0 || indexv > 0 ) url += indexh;
					if( indexv > 0 ) url += '/' + indexv;
				}

				window.location.hash = url;
			}
		}

	}

	/**
	 * Retrieves the h/v location 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 };

	}

	/**
	 * Retrieves the total number of slides in this presentation.
	 */
	function getTotalSlides() {

		return document.querySelectorAll( SLIDES_SELECTOR + ':not(.stack)' ).length;

	}

	/**
	 * Retrieves the current state of the presentation as
	 * an object. This state can then be restored at any
	 * time.
	 */
	function getState() {

		var indices = getIndices();

		return {
			indexh: indices.h,
			indexv: indices.v,
			indexf: indices.f,
			paused: isPaused(),
			overview: isOverview()
		};

	}

	/**
	 * Restores the presentation to the given state.
	 *
	 * @param {Object} state As generated by getState()
	 */
	function setState( state ) {

		if( typeof state === 'object' ) {
			slide( deserialize( state.indexh ), deserialize( state.indexv ), deserialize( state.indexf ) );

			var pausedFlag = deserialize( state.paused ),
				overviewFlag = deserialize( state.overview );

			if( typeof pausedFlag === 'boolean' && pausedFlag !== isPaused() ) {
				togglePause( pausedFlag );
			}

			if( typeof overviewFlag === 'boolean' && overviewFlag !== isOverview() ) {
				toggleOverview( overviewFlag );
			}
		}

	}

	/**
	 * Return a sorted fragments list, ordered by an increasing
	 * "data-fragment-index" attribute.
	 *
	 * Fragments will be revealed in the order that they are returned by
	 * this function, so you can use the index attributes to control the
	 * order of fragment appearance.
	 *
	 * To maintain a sensible default fragment order, fragments are presumed
	 * to be passed in document order. This function adds a "fragment-index"
	 * attribute to each node if such an attribute is not already present,
	 * and sets that attribute to an integer value which is the position of
	 * the fragment within the fragments list.
	 */
	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();
				updateProgress();

				return !!( fragmentsShown.length || fragmentsHidden.length );

			}

		}

		return false;

	}

	/**
	 * Navigate to the next slide fragment.
	 *
	 * @return {Boolean} true if there was a next fragment,
	 * false otherwise
	 */
	function nextFragment() {

		return navigateFragment( null, 1 );

	}

	/**
	 * Navigate to the previous slide fragment.
	 *
	 * @return {Boolean} true if there was a previous fragment,
	 * false otherwise
	 */
	function previousFragment() {

		return navigateFragment( null, -1 );

	}

	/**
	 * Cues a new automated slide if enabled in the config.
	 */
	function cueAutoSlide() {

		cancelAutoSlide();

		if( currentSlide ) {

			var currentFragment = currentSlide.querySelector( '.current-fragment' );

			var fragmentAutoSlide = currentFragment ? currentFragment.getAttribute( 'data-autoslide' ) : null;
			var parentAutoSlide = currentSlide.parentNode ? currentSlide.parentNode.getAttribute( 'data-autoslide' ) : null;
			var slideAutoSlide = currentSlide.getAttribute( 'data-autoslide' );

			// Pick value in the following priority order:
			// 1. Current fragment's data-autoslide
			// 2. Current slide's data-autoslide
			// 3. Parent slide's data-autoslide
			// 4. Global autoSlide setting
			if( fragmentAutoSlide ) {
				autoSlide = parseInt( fragmentAutoSlide, 10 );
			}
			else if( slideAutoSlide ) {
				autoSlide = parseInt( slideAutoSlide, 10 );
			}
			else if( parentAutoSlide ) {
				autoSlide = parseInt( parentAutoSlide, 10 );
			}
			else {
				autoSlide = config.autoSlide;
			}

			// If there are media elements with data-autoplay,
			// automatically set the autoSlide duration to the
			// length of that media
			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() {

		if( autoSlide && !autoSlidePaused ) {
			autoSlidePaused = true;
			dispatchEvent( 'autoslidepaused' );
			clearTimeout( autoSlideTimeout );

			if( autoSlidePlayer ) {
				autoSlidePlayer.setPlaying( false );
			}
		}

	}

	function resumeAutoSlide() {

		if( autoSlide && autoSlidePaused ) {
			autoSlidePaused = false;
			dispatchEvent( 'autoslideresumed' );
			cueAutoSlide();
		}

	}

	function navigateLeft() {

		// Reverse for RTL
		if( config.rtl ) {
			if( ( isOverview() || nextFragment() === false ) && availableRoutes().left ) {
				slide( indexh + 1 );
			}
		}
		// Normal navigation
		else if( ( isOverview() || previousFragment() === false ) && availableRoutes().left ) {
			slide( indexh - 1 );
		}

	}

	function navigateRight() {

		// 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 ) {

		// If there's a condition specified and it returns false,
		// ignore this event
		if( typeof config.keyboardCondition === 'function' && config.keyboardCondition() === false ) {
			return true;
		}

		// Remember if auto-sliding was paused so we can toggle it
		var autoSlideWasPaused = autoSlidePaused;

		onUserInput( event );

		// Check if there's a focused element that could be using
		// the keyboard
		var 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;
				// two-spot, semicolon, b, period, Logitech presenter tools "black screen" button
				case 58: case 59: case 66: case 190: case 191: togglePause(); break;
				// f
				case 70: enterFullscreen(); break;
				// a
				case 65: if ( config.autoSlideStoppable ) toggleAutoSlide( autoSlideWasPaused ); break;
				default:
					triggered = false;
			}

		}

		// If the input resulted in a triggered action we should prevent
		// the browsers default behavior
		if( triggered ) {
			event.preventDefault();
		}
		// ESC or O key
		else if ( ( event.keyCode === 27 || event.keyCode === 79 ) && features.transforms3d ) {
			if( dom.preview ) {
				closePreview();
			}
			else {
				toggleOverview();
			}