reveal.js

				// 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' );

						// Announce the fragments one by one to the Screen Reader
						dom.statusDiv.innerHTML = element.textContent;

						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 = dom.wrapper.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 'keypress' event.
	 */

	function onDocumentKeyPress( event ) {
		// Check if the pressed key is question mark
		if( event.shiftKey && event.charCode == 63 ) {
			openShortcutsOverlay();
		}
	}

	/**
	 * 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 activeElementIsCE = document.activeElement && document.activeElement.contentEditable !== 'inherit';
		var activeElementIsInput = document.activeElement && document.activeElement.tagName && /input|textarea/i.test( document.activeElement.tagName );

		// Disregard the event if there's a focused element or a
		// keyboard modifier key is present
		if( activeElementIsCE || activeElementIsInput || (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 && event.preventDefault();
		}
		// ESC or O key
		else if ( ( event.keyCode === 27 || event.keyCode === 79 ) && features.transforms3d ) {
			if( dom.preview ) {
				closePreview();
			}
			else {
				toggleOverview();
			}

			event.preventDefault && 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.pointerType === "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.pointerType === "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.pointerType === "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( dom.wrapper.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 --------------------------------//
	// --------------------------------------------------------------------//


	Reveal = {
		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,

		// Toggles the auto slide mode on/off
		toggleAutoSlide: toggleAutoSlide,

		// State checks
		isOverview: isOverview,
		isPaused: isPaused,
		isAutoSliding: isAutoSliding,

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

		// Facility for persisting and restoring the presentation state
		getState: getState,
		setState: setState,

		// Presentation progress on range of 0-1
		getProgress: getProgress,

		// Returns the indices of the current, or specified, slide
		getIndices: getIndices,

		getTotalSlides: getTotalSlides,

		// Returns the slide element at the specified index
		getSlide: getSlide,

		// Returns the slide background element at the specified index
		getSlideBackground: getSlideBackground,

		// 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();
			} );