reveal.js

			node.classList.remove( 'enabled' );
		} );

		// Add the 'enabled' class to the available routes
		if( routes.left ) dom.controlsLeft.classList.add( 'enabled' );
		if( routes.right ) dom.controlsRight.classList.add( 'enabled' );
		if( routes.up ) dom.controlsUp.classList.add( 'enabled' );
		if( routes.down ) dom.controlsDown.classList.add( 'enabled' );
	}

	/**
	 * 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 );

		return {
			left: indexh > 0,
			right: indexh < horizontalSlides.length - 1,
			up: indexv > 0,
			down: indexv < verticalSlides.length - 1
		};
	}
	
	/**
	 * 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 slide = document.querySelector( '#' + name );

			if( slide ) {
				// Find the position of the named slide and navigate to it
				var indices = Reveal.getIndices( slide );
				navigateTo( indices.h, indices.v );
			}
			// If the slide doesn't exist, navigate to the current slide
			else {
				navigateTo( indexh, indexv );
			}
		}
		else {
			// Read the index components of the hash
			var h = parseInt( bits[0], 10 ) || 0,
				v = parseInt( bits[1], 10 ) || 0;

			navigateTo( h, v );
		}
	}
	
	/**
	 * Updates the page URL (hash) to reflect the current
	 * state. 
	 */
	function writeURL() {
		if( config.history ) {
			var url = '/';
			
			// Only include the minimum possible number of components in
			// the URL
			if( indexh > 0 || indexv > 0 ) url += indexh;
			if( indexv > 0 ) url += '/' + indexv;
			
			window.location.hash = url;
		}
	}

	/**
	 * Navigate to the next slide fragment.
	 * 
	 * @return {Boolean} true if there was a next fragment,
	 * false otherwise
	 */
	function nextFragment() {
		// Vertical slides:
		if( document.querySelector( VERTICAL_SLIDES_SELECTOR + '.present' ) ) {
			var verticalFragments = document.querySelectorAll( VERTICAL_SLIDES_SELECTOR + '.present .fragment:not(.visible)' );
			if( verticalFragments.length ) {
				verticalFragments[0].classList.add( 'visible' );

				// Notify subscribers of the change
				dispatchEvent( 'fragmentshown', { fragment: verticalFragments[0] } );
				return true;
			}
		}
		// Horizontal slides:
		else {
			var horizontalFragments = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.present .fragment:not(.visible)' );
			if( horizontalFragments.length ) {
				horizontalFragments[0].classList.add( 'visible' );

				// Notify subscribers of the change
				dispatchEvent( 'fragmentshown', { fragment: horizontalFragments[0] } );
				return true;
			}
		}

		return false;
	}

	/**
	 * Navigate to the previous slide fragment.
	 * 
	 * @return {Boolean} true if there was a previous fragment,
	 * false otherwise
	 */
	function previousFragment() {
		// Vertical slides:
		if( document.querySelector( VERTICAL_SLIDES_SELECTOR + '.present' ) ) {
			var verticalFragments = document.querySelectorAll( VERTICAL_SLIDES_SELECTOR + '.present .fragment.visible' );
			if( verticalFragments.length ) {
				verticalFragments[ verticalFragments.length - 1 ].classList.remove( 'visible' );

				// Notify subscribers of the change
				dispatchEvent( 'fragmenthidden', { fragment: verticalFragments[ verticalFragments.length - 1 ] } );
				return true;
			}
		}
		// Horizontal slides:
		else {
			var horizontalFragments = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.present .fragment.visible' );
			if( horizontalFragments.length ) {
				horizontalFragments[ horizontalFragments.length - 1 ].classList.remove( 'visible' );

				// Notify subscribers of the change
				dispatchEvent( 'fragmenthidden', { fragment: horizontalFragments[ horizontalFragments.length - 1 ] } );
				return true;
			}
		}
		
		return false;
	}

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

		// Cue the next auto-slide if enabled
		if( autoSlide ) {
			autoSlideTimeout = setTimeout( navigateNext, autoSlide );
		}
	}
	
	/**
	 * Triggers a navigation to the specified indices.
	 * 
	 * @param {Number} h The horizontal index of the slide to show
	 * @param {Number} v The vertical index of the slide to show
	 */
	function navigateTo( h, v ) {
		slide( h, v );
	}
	
	function navigateLeft() {
		// Prioritize hiding fragments
		if( isOverviewActive() || previousFragment() === false ) {
			slide( indexh - 1, 0 );
		}
	}

	function navigateRight() {
		// Prioritize revealing fragments
		if( isOverviewActive() || nextFragment() === false ) {
			slide( indexh + 1, 0 );
		}
	}

	function navigateUp() {
		// Prioritize hiding fragments
		if( isOverviewActive() || previousFragment() === false ) {
			slide( indexh, indexv - 1 );
		}
	}

	function navigateDown() {
		// Prioritize revealing fragments
		if( isOverviewActive() || nextFragment() === false ) {
			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( '.reveal .slides>section.past:nth-child(' + indexh + ')' );

				if( previousSlide ) {
					indexv = ( previousSlide.querySelectorAll('section').length + 1 ) || 0;
					indexh --;
					slide();
				}
			}
		}
	}

	/**
	 * 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();
	}

	// Expose some methods publicly
	return {
		initialize: initialize,
		navigateTo: navigateTo,
		navigateLeft: navigateLeft,
		navigateRight: navigateRight,
		navigateUp: navigateUp,
		navigateDown: navigateDown,
		navigatePrev: navigatePrev,
		navigateNext: navigateNext,
		toggleOverview: toggleOverview,

		// Adds or removes all internal event listeners (such as keyboard)
		addEventListeners: addEventListeners,
		removeEventListeners: removeEventListeners,

		// Returns the indices of the current, or specified, slide
		getIndices: function( slide ) {
			// By default, return the current indices
			var h = indexh,
				v = indexv;

			// If a slide is specified, return the indices of that slide
			if( slide ) {
				var isVertical = !!slide.parentNode.nodeName.match( /section/gi );
				var slideh = isVertical ? slide.parentNode : slide;

				// Select all horizontal slides
				var horizontalSlides = Array.prototype.slice.call( 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( Array.prototype.slice.call( slide.parentNode.children ).indexOf( slide ), 0 );
				}
			}

			return { h: h, v: v };
		},

		// Returns the previous slide element, may be null
		getPreviousSlide: function() {
			return previousSlide;
		},

		// Returns the current slide element
		getCurrentSlide: function() {
			return currentSlide;
		},

		// 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();
			} );

			return query;
		},

		// 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 );
			}
		}
	};
	
})();