diff --git a/inst/NEWS b/inst/NEWS
index 46058bb..dfb9c84 100644
--- a/inst/NEWS
+++ b/inst/NEWS
@@ -1,3 +1,9 @@
+Version 0.8 (unreleased)
+-----------------------------------------------------------------------
+
+- Add support for the chalkboard plugin
+
+
 Version 0.7
 -----------------------------------------------------------------------
 
diff --git a/inst/reveal.js-3.3.0/plugin/chalkboard/chalkboard.js b/inst/reveal.js-3.3.0/plugin/chalkboard/chalkboard.js
new file mode 100644
index 0000000..238363f
--- /dev/null
+++ b/inst/reveal.js-3.3.0/plugin/chalkboard/chalkboard.js
@@ -0,0 +1,1067 @@
+/*****************************************************************
+** Author: Asvin Goel, goel@telematique.eu
+**
+** A plugin for reveal.js adding a chalkboard. 
+**
+** Version: 0.5
+** 
+** License: MIT license (see LICENSE.md)
+**
+** Credits: 
+** Chalkboard effect by Mohamed Moustafa https://github.com/mmoustafa/Chalkboard
+******************************************************************/
+
+var RevealChalkboard = window.RevealChalkboard || (function(){
+	var path = scriptPath();
+	function scriptPath() {
+		// obtain plugin path from the script element
+		var src;
+		if (document.currentScript) {
+			src = document.currentScript.src;
+		} else {
+			var sel = document.querySelector('script[src$="/chalkboard.js"]')
+			if (sel) {
+				src = sel.src;
+			}
+		}
+
+		var path = typeof src === undefined ? src
+			: src.slice(0, src.lastIndexOf("/") + 1);
+//console.log("Path: " + path);
+		return path;
+}
+
+/*****************************************************************
+** Configuration
+******************************************************************/
+	var config = Reveal.getConfig().chalkboard || {};
+
+	var background, pen, draw, color;
+	var theme = config.theme || "chalkboard"; 
+	switch ( theme ) {
+		case "whiteboard":
+			background = [ 'rgba(127,127,127,.1)' , path + 'img/whiteboard.png' ];
+			pen = [ 'url(' + path + 'img/boardmarker.png), auto',
+				'url(' + path + 'img/boardmarker.png), auto' ];
+			draw = [ drawWithPen , drawWithPen ];
+			color = [ 'rgba(0,0,255,1)', 'rgba(0,0,255,1)' ];
+			break;
+		default:
+			background = [ 'rgba(127,127,127,.1)' , path + 'img/blackboard.png' ];
+			pen = [ 'url(' + path + 'img/boardmarker.png), auto',
+				'url(' + path + 'img/chalk.png), auto' ];
+			draw = [ drawWithPen , drawWithChalk ];
+			color = [ 'rgba(0,0,255,1)', 'rgba(255,255,255,0.5)'  ];
+	}
+	
+	if ( config.background ) background = config.background;
+	if ( config.pen ) pen = config.pen;
+	if ( config.draw ) draw = config.draw;
+	if ( config.color ) color = config.color;
+
+	var toggleChalkboardButton = config.toggleChalkboardButton == undefined ? true : config.toggleChalkboardButton;
+	var toggleNotesButton = config.toggleNotesButton == undefined ? true : config.toggleNotesButton;
+	var transition = config.transition  || 800;
+
+	var readOnly = config.readOnly;
+
+	var legacyFileSupport = config.legacyFileSupport;
+	if ( legacyFileSupport ) { console.warn("Legacy file support is deprecated and may be removed in future versions!") }
+
+/*****************************************************************
+** Setup
+******************************************************************/
+
+	var eraserDiameter = 20;
+
+	if ( toggleChalkboardButton ) {
+//console.log("toggleChalkboardButton")
+		var button = document.createElement( 'div' );
+		button.className = "chalkboard-button";
+		button.id = "toggle-chalkboard";
+		button.style.vivibility = "visible";
+		button.style.position = "absolute";
+		button.style.zIndex = 30;
+		button.style.fontSize = "24px";
+
+		button.style.left = toggleChalkboardButton.left || "30px";
+		button.style.bottom = toggleChalkboardButton.bottom ||  "30px";
+		button.style.top = toggleChalkboardButton.top ||  "auto";
+		button.style.right = toggleChalkboardButton.right ||  "auto";
+
+		button.innerHTML = '<a href="#" onclick="RevealChalkboard.toggleChalkboard(); return false;"><i class="fa fa-pencil-square-o"></i></a>'
+		document.querySelector(".reveal").appendChild( button );
+	}
+	if ( toggleNotesButton ) {
+//console.log("toggleNotesButton")
+		var button = document.createElement( 'div' );
+		button.className = "chalkboard-button";
+		button.id = "toggle-notes";
+		button.style.position = "absolute";
+		button.style.zIndex = 30;
+		button.style.fontSize = "24px";
+
+		button.style.left = toggleNotesButton.left || "70px";
+		button.style.bottom = toggleNotesButton.bottom ||  "30px";
+		button.style.top = toggleNotesButton.top ||  "auto";
+		button.style.right = toggleNotesButton.right ||  "auto";
+
+		button.innerHTML = '<a href="#" onclick="RevealChalkboard.toggleNotesCanvas(); return false;"><i class="fa fa-pencil"></i></a>'
+		document.querySelector(".reveal").appendChild( button );
+	}
+//alert("Buttons");
+
+	var drawingCanvas = [ {id: "notescanvas" }, {id: "chalkboard" } ];
+	setupDrawingCanvas(0);
+	setupDrawingCanvas(1);
+
+	var mode = 0; // 0: notes canvas, 1: chalkboard
+
+	var mouseX = 0;
+	var mouseY = 0;
+	var xLast = null;
+	var yLast = null;
+
+	var slideStart = Date.now();
+	var slideIndices =  { h:0, v:0 };
+        var event = null;
+        var timeouts = [ [], [] ];
+	var touchTimeout = null;
+	var slidechangeTimeout = null;
+	var playback = false;
+
+	function setupDrawingCanvas( id ) {
+		var container = document.createElement( 'div' );
+		container.id = drawingCanvas[id].id;
+		container.classList.add( 'overlay' );
+		container.setAttribute( 'data-prevent-swipe', '' );
+		container.oncontextmenu = function() { return false; } 
+		container.style.cursor = pen[ id ];
+
+		drawingCanvas[id].width = window.innerWidth;
+		drawingCanvas[id].height = window.innerHeight;
+		drawingCanvas[id].scale = 1;
+		drawingCanvas[id].xOffset = 0;
+		drawingCanvas[id].yOffset = 0;
+
+
+		if ( id == "0" ) {
+			container.style.background = 'rgba(0,0,0,0)';
+			container.style.zIndex = "24";
+			container.classList.add( 'visible' )
+			container.style.pointerEvents = "none";
+
+			var slides = document.querySelector(".slides");
+			var aspectRatio = Reveal.getConfig().width / Reveal.getConfig().height;
+			if ( drawingCanvas[id].width > drawingCanvas[id].height*aspectRatio ) {
+				drawingCanvas[id].xOffset = (drawingCanvas[id].width - drawingCanvas[id].height*aspectRatio) / 2;
+			}
+			else if ( drawingCanvas[id].height > drawingCanvas[id].width/aspectRatio ) {
+				drawingCanvas[id].yOffset = ( drawingCanvas[id].height - drawingCanvas[id].width/aspectRatio ) / 2;
+			}
+		}
+		else {
+			container.style.background = 'url("' + background[id] + '") repeat';
+			container.style.zIndex = "26";
+		}
+
+		var sponge = document.createElement( 'img' );
+		sponge.src = path + 'img/sponge.png';
+		sponge.id = "sponge";
+		sponge.style.visibility = "hidden";
+		sponge.style.position = "absolute";
+		container.appendChild( sponge );
+		drawingCanvas[id].sponge = sponge;
+
+		var canvas = document.createElement( 'canvas' );
+		canvas.width = drawingCanvas[id].width;
+		canvas.height = drawingCanvas[id].height;
+		canvas.setAttribute( 'data-chalkboard', id );
+		canvas.style.cursor = pen[ id ];
+		container.appendChild( canvas );
+		drawingCanvas[id].canvas = canvas;
+
+		drawingCanvas[id].context = canvas.getContext("2d");
+
+
+		document.querySelector( '.reveal' ).appendChild( container );
+		drawingCanvas[id].container = container;
+	}
+
+
+/*****************************************************************
+** Storage
+******************************************************************/
+	var storage = [
+			{ width: drawingCanvas[0].width - 2 * drawingCanvas[0].xOffset, height: drawingCanvas[0].height - 2 * drawingCanvas[0].yOffset, data: []},
+			{ width: drawingCanvas[1].width, height: drawingCanvas[1].height, data: []}
+		];
+//console.log( JSON.stringify(storage));
+
+	if ( config.src != null ) {
+		loadData( config.src );
+	}
+
+
+	/**
+	 * Load data.
+	 */
+	function loadData( filename ) {
+		var xhr = new XMLHttpRequest();
+		xhr.onload = function() {
+			if (xhr.readyState === 4) {
+				storage = JSON.parse(xhr.responseText);
+				for (var id = 0; id < storage.length; id++) {
+					if ( drawingCanvas[id].width != storage[id].width || drawingCanvas[id].height != storage[id].height ) {
+						drawingCanvas[id].scale = Math.min( drawingCanvas[id].width/storage[id].width, drawingCanvas[id].height/storage[id].height);
+						drawingCanvas[id].xOffset = (drawingCanvas[id].width - storage[id].width * drawingCanvas[id].scale)/2;
+						drawingCanvas[id].yOffset = (drawingCanvas[id].height - storage[id].height * drawingCanvas[id].scale)/2;
+					}
+					if ( config.readOnly ) {
+						drawingCanvas[id].container.style.cursor = 'default';
+						drawingCanvas[id].canvas.style.cursor = 'default';
+					}
+				}
+//console.log("Drawings loaded");
+			}
+			else {
+				config.readOnly = undefined;
+				readOnly = undefined;
+				console.warn( 'Failed to get file ' + filename +". ReadyState: " + xhr.readyState + ", Status: " + xhr.status);
+			}
+		};
+
+		xhr.open( 'GET', filename, true );
+		try {
+			xhr.send();
+		}
+		catch ( error ) {
+			config.readOnly = undefined;
+			readOnly = undefined;
+			console.warn( 'Failed to get file ' + filename + '. Make sure that the presentation and the file are served by a HTTP server and the file can be found there. ' + error );
+		}
+	}
+
+	/**
+	 * Download data.
+	 */
+	function downloadData() {
+		var a = document.createElement('a');
+		document.body.appendChild(a);	
+		try {
+			// cleanup slide data without events
+			for (var id = 0; id < 2; id++) {
+				for (var i = storage[id].data.length-1; i >= 0; i--) {
+					if (storage[id].data[i].events.length == 0) {
+						storage[id].data.splice(i, 1);
+					}
+				}
+			}
+			a.download = "chalkboard.json";
+			var blob = new Blob( [ JSON.stringify( storage ) ], { type: "application/json"} );
+			a.href = window.URL.createObjectURL( blob );
+		} catch( error ) {
+			a.innerHTML += " (" + error + ")";
+		}
+		a.click();
+		document.body.removeChild(a);
+	}
+
+	/**
+	 * Returns data object for the slide with the given indices.
+	 */
+	function getSlideData( indices, id ) {
+		if ( id == undefined ) id = mode;
+		if (!indices) indices = slideIndices;
+		var data;
+		for (var i = 0; i < storage[id].data.length; i++) {
+			if (storage[id].data[i].slide.h === indices.h && storage[id].data[i].slide.v === indices.v && storage[id].data[i].slide.f === indices.f ) {
+				data = storage[id].data[i];
+				return data;
+			}
+			if ( !legacyFileSupport && 
+			     ( storage[id].data[i].slide.h > indices.h || 
+                               ( storage[id].data[i].slide.h === indices.h && storage[id].data[i].slide.v > indices.v ) || 
+			       ( storage[id].data[i].slide.h === indices.h && storage[id].data[i].slide.v === indices.v && storage[id].data[i].slide.f > indices.f ) 
+			     )
+			   ) {
+				storage[id].data.splice( i, 0, { slide: indices, events: [], duration: 0 } );
+				data = storage[id].data[i];
+				return data;
+			}
+		}
+		storage[id].data.push( { slide: indices, events: [], duration: 0 } );
+		data = storage[id].data[storage[id].data.length-1];
+		return data;
+	}
+
+	/**
+	 * Returns maximum duration of slide playback for both modes
+	 */
+	function getSlideDuration( indices ) {
+		if (!indices) indices = slideIndices;
+		var duration = 0;
+		for (var id = 0; id < 2; id++) {
+			for (var i = 0; i < storage[id].data.length; i++) {
+				if (storage[id].data[i].slide.h === indices.h && storage[id].data[i].slide.v === indices.v && storage[id].data[i].slide.f === indices.f ) {
+					duration = Math.max( duration, storage[id].data[i].duration );
+					break;
+				}
+			}
+		}
+//console.log( duration );
+		return duration;
+	}
+
+/*****************************************************************
+** Print
+******************************************************************/
+	var printMode = ( /print-pdf/gi ).test( window.location.search );
+//console.log("createPrintout" + printMode)
+
+	function createPrintout( ) {
+//console.log( 'Create printout for ' + storage[1].data.length + " slides");
+		drawingCanvas[0].container.classList.remove( 'visible' ); // do not print notes canvas
+
+		var patImg = new Image(); 
+		patImg.onload = function () {
+			var nextSlide = [];
+			var width = Reveal.getConfig().width;
+			var height = Reveal.getConfig().height;
+			var scale = 1;
+			var xOffset = 0;
+			var yOffset = 0;
+			if ( width != storage[1].width || height != storage[1].height ) {
+				scale = Math.min( width/storage[1].width, height/storage[1].height);
+				xOffset = (width - storage[1].width * scale)/2;
+				yOffset = (height - storage[1].height * scale)/2;
+			}
+
+			for (var i = 0; i < storage[1].data.length; i++) {
+				var slide = Reveal.getSlide( storage[1].data[i].slide.h, storage[1].data[i].slide.v );
+				nextSlide.push( slide.nextSibling );
+			}
+			for (var i = 0; i < storage[1].data.length; i++) {
+				var slideData = getSlideData( storage[1].data[i].slide, 1 );
+
+				var imgCanvas = document.createElement('canvas');
+				imgCanvas.width = width;
+				imgCanvas.height = height;
+
+				var imgCtx = imgCanvas.getContext("2d");
+				imgCtx.fillStyle = imgCtx.createPattern( patImg ,'repeat');
+				imgCtx.rect(0,0,imgCanvas.width,imgCanvas.height);
+				imgCtx.fill();
+
+				for (var j = 0; j < slideData.events.length; j++) {
+					switch ( slideData.events[j].type ) {
+						case "draw":
+							for (var k = 1; k < slideData.events[j].curve.length; k++) {
+								draw[1]( imgCtx, 
+									xOffset + slideData.events[j].curve[k-1].x*scale, 
+									yOffset + slideData.events[j].curve[k-1].y*scale, 
+									xOffset + slideData.events[j].curve[k].x*scale, 
+									yOffset + slideData.events[j].curve[k].y*scale
+								);
+							}
+							break;
+						case "erase":
+							for (var k = 0; k < slideData.events[j].curve.length; k++) {
+								erase( imgCtx, 
+									xOffset + slideData.events[j].curve[k].x*scale, 
+									yOffset + slideData.events[j].curve[k].y*scale
+								);
+							}
+							break;
+						case "clear":
+							addPrintout( nextSlide[i], imgCanvas, patImg );
+							imgCtx.clearRect(0,0,imgCanvas.width,imgCanvas.height);
+							imgCtx.fill();
+							break;
+						default:
+							break;
+					}
+				}
+				if ( slideData.events.length ) {
+					addPrintout( nextSlide[i], imgCanvas, patImg );
+				}
+			} 
+			Reveal.sync();
+		};
+		patImg.src = background[1];
+	}
+
+	function addPrintout( nextSlide, imgCanvas, patImg ) {
+		var slideCanvas = document.createElement('canvas');
+		slideCanvas.width = Reveal.getConfig().width;
+		slideCanvas.height = Reveal.getConfig().height;	
+		var ctx = slideCanvas.getContext("2d");
+		ctx.fillStyle = ctx.createPattern( patImg ,'repeat');
+		ctx.rect(0,0,slideCanvas.width,slideCanvas.height);
+		ctx.fill();
+		ctx.drawImage(imgCanvas, 0, 0);
+
+		var newSlide = document.createElement( 'section' );
+		newSlide.classList.add( 'present' );
+		newSlide.innerHTML = '<h1 style="visibility:hidden">Drawing</h1>';
+		newSlide.setAttribute("data-background-size", '100% 100%' );
+		newSlide.setAttribute("data-background-repeat", 'norepeat' );
+		newSlide.setAttribute("data-background", 'url("' + slideCanvas.toDataURL("image/png") +'")' );
+		nextSlide.parentElement.insertBefore( newSlide, nextSlide );
+	}
+
+/*****************************************************************
+** Drawings
+******************************************************************/
+
+	function drawWithPen(context,fromX,fromY,toX,toY){
+		context.lineWidth = 3;
+		context.lineCap = 'round';
+		context.strokeStyle = color[0];
+		context.beginPath();
+  		context.moveTo(fromX, fromY);		
+  		context.lineTo(toX, toY);
+  		context.stroke();
+	}
+
+	function drawWithChalk(context,fromX,fromY,toX,toY){
+		var brushDiameter = 7;
+		context.lineWidth = brushDiameter;
+		context.lineCap = 'round';
+		context.fillStyle = color[1]; // 'rgba(255,255,255,0.5)';	
+		context.strokeStyle = color[1];
+		var opacity = Math.min(0.8, Math.max(0,color[1].replace(/^.*,(.+)\)/,'$1') - 0.1)) + Math.random()*0.2;
+		context.strokeStyle = context.strokeStyle.replace(/[\d\.]+\)$/g, opacity + ')');
+		context.beginPath();
+  		context.moveTo(fromX, fromY);		
+  		context.lineTo(toX, toY);
+  		context.stroke();
+  		// Chalk Effect
+		var length = Math.round(Math.sqrt(Math.pow(toX-fromX,2)+Math.pow(toY-fromY,2))/(5/brushDiameter));
+		var xUnit = (toX-fromX)/length;
+		var yUnit = (toY-fromY)/length;
+		for(var i=0; i<length; i++ ){
+			var xCurrent = fromX+(i*xUnit);	
+			var yCurrent = fromY+(i*yUnit);
+			var xRandom = xCurrent+(Math.random()-0.5)*brushDiameter*1.2;			
+			var yRandom = yCurrent+(Math.random()-0.5)*brushDiameter*1.2;
+	    		context.clearRect( xRandom, yRandom, Math.random()*2+2, Math.random()+1);
+		}
+	}
+	function erase(context,x,y){
+		context.save();
+		context.beginPath();
+		context.arc(x, y, eraserDiameter, 0, 2 * Math.PI, false);
+		context.clip();
+		context.clearRect(x - eraserDiameter - 1, y - eraserDiameter - 1, eraserDiameter * 2 + 2, eraserDiameter * 2 + 2);
+		context.restore();
+
+	}
+
+
+	/**
+	 * Opens an overlay for the chalkboard.
+	 */
+	function showChalkboard() {
+//console.log("showChalkboard");
+		clearTimeout(touchTimeout);
+		touchTimeout = null;
+		drawingCanvas[0].sponge.style.visibility = "hidden"; // make sure that the sponge from touch events is hidden
+		drawingCanvas[1].sponge.style.visibility = "hidden"; // make sure that the sponge from touch events is hidden
+		drawingCanvas[1].container.classList.add( 'visible' );
+		mode = 1;
+	}
+
+
+	/**
+	 * Closes open chalkboard.
+	 */
+	function closeChalkboard() {
+		clearTimeout(touchTimeout);
+		touchTimeout = null;
+		drawingCanvas[0].sponge.style.visibility = "hidden"; // make sure that the sponge from touch events is hidden
+		drawingCanvas[1].sponge.style.visibility = "hidden"; // make sure that the sponge from touch events is hidden
+		drawingCanvas[1].container.classList.remove( 'visible' );
+		xLast = null;
+		yLast = null;
+		event = null;
+		mode = 0;
+	}
+
+	/**
+	 * Clear current canvas.
+	 */
+	function clearCanvas( id ) {
+		if ( id == 0 ) clearTimeout( slidechangeTimeout );
+		drawingCanvas[id].context.clearRect(0,0,drawingCanvas[id].width,drawingCanvas[id].height);
+	}
+
+/*****************************************************************
+** Playback
+******************************************************************/
+
+	document.addEventListener('seekplayback', function( event ) {
+//console.log('event seekplayback ' + event.timestamp);
+		stopPlayback();				
+		if ( !playback || event.timestamp == 0) {
+			// in other cases startplayback fires after seeked
+			startPlayback( event.timestamp );				
+		}
+//console.log('seeked');
+	});
+
+
+	document.addEventListener('startplayback', function( event ) {
+//console.log('event startplayback ' + event.timestamp);
+		stopPlayback();				
+		playback = true;
+		startPlayback( event.timestamp );				
+	});
+
+	document.addEventListener('stopplayback', function( event ) {
+//console.log('event stopplayback ' + (Date.now() - slideStart) );
+		playback = false;
+		stopPlayback();				
+	});
+
+	document.addEventListener('startrecording', function( event ) {
+//console.log('event startrecording ' + event.timestamp);
+		startRecording();				
+	});
+
+	function recordEvent( event ) {
+		var slideData = getSlideData();
+		var i = slideData.events.length;
+		while ( i > 0 && event.begin < slideData.events[i-1].begin ) {
+			i--;
+		}
+		slideData.events.splice( i, 0, event);
+		slideData.duration = Math.max( slideData.duration, Date.now() - slideStart ) + 1;
+	}
+
+	function startRecording() {
+		resetSlide( true );
+		updateReadOnlyMode();
+		slideStart = Date.now();
+	}
+
+	function startPlayback( timestamp, finalMode, resized ) {
+//console.log("playback " + timestamp );
+		if ( resized == undefined ) {
+			updateReadOnlyMode();			
+		}
+		slideStart = Date.now() - timestamp;
+		closeChalkboard();
+		mode = 0;		
+		for ( var id = 0; id < 2; id++ ) {
+			clearCanvas( id );
+			var slideData = getSlideData( slideIndices, id );
+//console.log( timestamp +" / " + JSON.stringify(slideData));
+			var index = 0;
+			while ( index < slideData.events.length && slideData.events[index].begin < (Date.now() - slideStart) ) {
+				playEvent( id, slideData.events[index], timestamp );
+				index++;
+			} 
+
+			while ( playback && index < slideData.events.length ) {
+				timeouts[id].push( setTimeout( playEvent, slideData.events[index].begin - (Date.now() - slideStart), id, slideData.events[index], timestamp ) );
+				index++;
+			}
+		} 
+//console.log("Mode: " + finalMode + "/" + mode );
+		if ( finalMode != undefined ) {
+			mode = finalMode;
+		}
+		if( mode == 1 ) showChalkboard();
+//console.log("playback (ok)");
+		
+	};
+
+	function stopPlayback() {
+//console.log("stopPlayback");
+//console.log("Timeouts: " + timeouts[0].length + "/"+ timeouts[1].length);
+		for ( var id = 0; id < 2; id++ ) {
+			for (var i = 0; i < timeouts[id].length; i++) {
+ 				clearTimeout(timeouts[id][i]);
+			}
+			timeouts[id] = [];
+		}
+	};
+
+	function playEvent( id, event, timestamp ) {
+//console.log( timestamp +" / " + JSON.stringify(event));
+//console.log( id + ": " + timestamp +" / " +  event.begin +" / " + event.type +" / " + mode );
+		switch ( event.type ) {
+			case "open":
+				if ( timestamp <= event.begin ) {
+					showChalkboard();
+				}
+				else { 
+					mode = 1;
+				}
+	
+				break;
+			case "close":
+				if ( timestamp < event.begin ) {
+					closeChalkboard();
+				}
+				else { 
+					mode = 0;
+				}
+				break;
+			case "clear":
+				clearCanvas( id );
+				break;
+			case "draw":
+				drawCurve( id, event, timestamp );
+				break;
+			case "erase":
+				eraseCurve( id, event, timestamp );
+				break;
+
+		}
+	};
+
+	function drawCurve( id, event, timestamp ) {
+		if  ( event.curve.length > 1 ) {
+			var ctx = drawingCanvas[id].context;
+			var scale = drawingCanvas[id].scale;
+			var xOffset = drawingCanvas[id].xOffset;
+			var yOffset = drawingCanvas[id].yOffset;
+
+			var stepDuration = ( event.end - event.begin )/ ( event.curve.length - 1 );
+//console.log("---");
+			for (var i = 1; i < event.curve.length; i++) {
+				if (event.begin + i * stepDuration <= (Date.now() - slideStart)) {
+//console.log( "Draw " + timestamp +" / " + event.begin + " + " + i + " * " + stepDuration );
+					draw[id](ctx, xOffset + event.curve[i-1].x*scale, yOffset + event.curve[i-1].y*scale, xOffset + event.curve[i].x*scale, yOffset + event.curve[i].y*scale); 
+				}
+				else if ( playback ) {
+//console.log( "Cue " + timestamp +" / " + (Date.now() - slideStart) +" / " + event.begin + " + " + i + " * " + stepDuration + " = " + Math.max(0,event.begin + i * stepDuration - timestamp) );
+					timeouts.push( setTimeout( 
+						draw[id], Math.max(0,event.begin + i * stepDuration - (Date.now() - slideStart)), ctx, 
+							xOffset + event.curve[i-1].x*scale,	
+							yOffset + event.curve[i-1].y*scale, 
+							xOffset + event.curve[i].x*scale, 
+							yOffset + event.curve[i].y*scale 
+						) 
+					);
+				}
+			}
+		}
+
+	};
+
+	function eraseCurve( id, event, timestamp ) {
+		if  ( event.curve.length > 1 ) {
+			var ctx = drawingCanvas[id].context;
+			var scale = drawingCanvas[id].scale;
+			var xOffset = drawingCanvas[id].xOffset;
+			var yOffset = drawingCanvas[id].yOffset;
+
+			var stepDuration = ( event.end - event.begin )/ event.curve.length;
+			for (var i = 0; i < event.curve.length; i++) {
+				if (event.begin + i * stepDuration <= (Date.now() - slideStart)) {
+					erase(ctx, xOffset + event.curve[i].x*scale, yOffset + event.curve[i].y*scale); 
+				}
+				else if ( playback ) {
+					timeouts.push( setTimeout( 
+						erase, Math.max(0,event.begin + i * stepDuration - (Date.now() - slideStart)), ctx, 
+							xOffset + event.curve[i].x * scale, 
+							yOffset + event.curve[i].y * scale 
+						) 
+					);
+				}
+			}
+		}
+
+	};
+
+/*****************************************************************
+** User interface
+******************************************************************/
+
+
+// TODO: check all touchevents
+	document.addEventListener('touchstart', function(evt) {
+		if ( !readOnly && evt.target.getAttribute('data-chalkboard') == mode ) {
+			var ctx = drawingCanvas[mode].context;
+			var scale = drawingCanvas[mode].scale;
+			var xOffset = drawingCanvas[mode].xOffset;
+			var yOffset = drawingCanvas[mode].yOffset;
+
+			evt.preventDefault();
+		        var touch = evt.touches[0];
+		        mouseX = touch.pageX;
+		        mouseY = touch.pageY;
+			xLast = mouseX;
+			yLast = mouseY;
+			event = { type: "draw", begin: Date.now() - slideStart, end: null, curve: [{x: (mouseX - xOffset)/scale, y: (mouseY-yOffset)/scale}] };
+			touchTimeout = setTimeout( showSponge, 500, mouseX, mouseY );
+		}	
+	}, false);
+
+	document.addEventListener('touchmove', function(evt) {
+		clearTimeout( touchTimeout );
+		touchTimeout = null;
+		if ( event ) {
+			var ctx = drawingCanvas[mode].context;
+			var scale = drawingCanvas[mode].scale;
+			var xOffset = drawingCanvas[mode].xOffset;
+			var yOffset = drawingCanvas[mode].yOffset;
+
+		        var touch = evt.touches[0];
+        		mouseX = touch.pageX;
+        		mouseY = touch.pageY;
+        		if (mouseY < drawingCanvas[mode].height && mouseX < drawingCanvas[mode].width) {
+        		    evt.preventDefault();
+				event.curve.push({x: (mouseX - xOffset)/scale, y: (mouseY-yOffset)/scale});
+				if ( event.type == "erase" ) {
+					drawingCanvas[mode].sponge.style.left = (mouseX - eraserDiameter) +"px" ; 
+					drawingCanvas[mode].sponge.style.top = (mouseY - eraserDiameter) +"px" ; 
+			                erase(ctx, mouseX, mouseY);
+				}
+				else {
+			                draw[mode](ctx, xLast, yLast, mouseX, mouseY);
+				}
+				xLast = mouseX;
+				yLast = mouseY;
+			}
+		}
+	}, false);
+
+	document.addEventListener('touchend', function(evt) {
+		clearTimeout( touchTimeout );
+		touchTimeout = null;
+		// hide sponge image
+		drawingCanvas[mode].sponge.style.visibility = "hidden"; 
+		if ( event ) {
+			event.end = Date.now() - slideStart;
+			if ( event.type == "erase" || event.curve.length > 1 ) {
+				// do not save a line with a single point only
+				recordEvent( event );
+			}
+			event = null;
+		}
+	}, false);
+
+	function showSponge(x,y) {
+		if ( event ) {
+			event.type = "erase";
+			event.begin = Date.now() - slideStart;
+			// show sponge image 
+			drawingCanvas[mode].sponge.style.left = (x - eraserDiameter) +"px" ;
+			drawingCanvas[mode].sponge.style.top = (y - eraserDiameter) +"px" ;
+			drawingCanvas[mode].sponge.style.visibility = "visible";
+			erase(drawingCanvas[mode].context,x,y);
+		}
+	}
+
+	document.addEventListener( 'mousedown', function( evt ) {
+//console.log( "Read only: " + readOnly );
+		if ( !readOnly && evt.target.getAttribute('data-chalkboard') == mode ) {
+//console.log( "mousedown: " + evt.target.getAttribute('data-chalkboard') );
+			var ctx = drawingCanvas[mode].context;
+			var scale = drawingCanvas[mode].scale;
+			var xOffset = drawingCanvas[mode].xOffset;
+			var yOffset = drawingCanvas[mode].yOffset;
+
+			mouseX = evt.pageX;
+			mouseY = evt.pageY;
+			xLast = mouseX;
+			yLast = mouseY;
+			if ( evt.button == 2) {
+				event = { type: "erase", begin: Date.now() - slideStart, end: null, curve: [{x: (mouseX - xOffset)/scale, y: (mouseY-yOffset)/scale}]};
+				drawingCanvas[mode].canvas.style.cursor = 'url("' + path + 'img/sponge.png") ' + eraserDiameter + ' ' + eraserDiameter + ', auto';
+				erase(ctx,mouseX,mouseY);
+			}
+			else {
+				event = { type: "draw", begin: Date.now() - slideStart, end: null, curve: [{x: (mouseX - xOffset)/scale, y: (mouseY-yOffset)/scale}] };
+			}		
+		}
+	} );
+
+	document.addEventListener( 'mousemove', function( evt ) {
+		if ( event ) {
+			var ctx = drawingCanvas[mode].context;
+			var scale = drawingCanvas[mode].scale;
+			var xOffset = drawingCanvas[mode].xOffset;
+			var yOffset = drawingCanvas[mode].yOffset;
+
+			mouseX = evt.pageX;
+			mouseY = evt.pageY;
+			event.curve.push({x: (mouseX - xOffset)/scale, y: (mouseY-yOffset)/scale});
+			if(mouseY < drawingCanvas[mode].height && mouseX < drawingCanvas[mode].width) {
+				if ( event.type == "erase" ) {
+					erase(ctx,mouseX,mouseY);
+				}
+				else {
+					draw[mode](ctx, xLast, yLast, mouseX,mouseY);
+				}
+				xLast = mouseX;
+				yLast = mouseY;
+			}
+		}
+	} );
+
+	document.addEventListener( 'mouseup', function( evt ) {
+		drawingCanvas[mode].canvas.style.cursor = pen[mode];
+		if ( event ) {
+			if(evt.button == 2){
+			}
+			event.end = Date.now() - slideStart;
+			if ( event.type == "erase" || event.curve.length > 1 ) {
+				// do not save a line with a single point only
+				recordEvent( event );
+			}
+			event = null;
+		}
+	} );
+
+	window.addEventListener( "resize", function() {
+//console.log("resize");
+		// Resize the canvas and draw everything again
+		var timestamp = Date.now() - slideStart;
+	        if ( !playback ) {
+			timestamp = getSlideDuration();
+		}
+
+//console.log( drawingCanvas[0].scale + "/" + drawingCanvas[0].xOffset + "/" +drawingCanvas[0].yOffset );
+		for (var id = 0; id < 2; id++ ) {
+			drawingCanvas[id].width  = window.innerWidth;
+			drawingCanvas[id].height = window.innerHeight;
+			drawingCanvas[id].canvas.width  = drawingCanvas[id].width;
+			drawingCanvas[id].canvas.height = drawingCanvas[id].height;
+			drawingCanvas[id].context.canvas.width  = drawingCanvas[id].width;
+			drawingCanvas[id].context.canvas.height = drawingCanvas[id].height;
+
+			drawingCanvas[id].scale = Math.min( drawingCanvas[id].width/storage[id].width, drawingCanvas[id].height/storage[id].height );
+			drawingCanvas[id].xOffset = (drawingCanvas[id].width - storage[id].width * drawingCanvas[id].scale)/2;
+			drawingCanvas[id].yOffset = (drawingCanvas[id].height - storage[id].height * drawingCanvas[id].scale)/2;
+//console.log( drawingCanvas[id].scale + "/" + drawingCanvas[id].xOffset + "/" +drawingCanvas[id].yOffset );
+		}
+//console.log( window.innerWidth + "/" + window.innerHeight);
+		startPlayback( timestamp, mode, true );
+
+	} );
+
+	function updateReadOnlyMode() {
+//console.log("updateReadOnlyMode");
+		if ( config.readOnly == undefined ) {
+			readOnly = ( getSlideDuration() > 0 );	
+			if ( readOnly ) {
+				drawingCanvas[0].container.style.cursor = 'default';
+				drawingCanvas[1].container.style.cursor = 'default';
+				drawingCanvas[0].canvas.style.cursor = 'default';
+				drawingCanvas[1].canvas.style.cursor = 'default';
+				if ( notescanvas.style.pointerEvents != "none" ) {
+					event = null;
+					notescanvas.style.background = 'rgba(0,0,0,0)';
+					notescanvas.style.pointerEvents = "none";
+				}
+	
+			}
+			else {
+				drawingCanvas[0].container.style.cursor = pen[0];
+				drawingCanvas[1].container.style.cursor = pen[1];
+				drawingCanvas[0].canvas.style.cursor = pen[0];
+				drawingCanvas[1].canvas.style.cursor = pen[1];
+			}
+		}
+	}
+
+	Reveal.addEventListener( 'ready', function( evt ) {
+//console.log('ready');
+		if ( !printMode ) {
+			slideStart = Date.now();
+			slideIndices = Reveal.getIndices();
+			if ( !playback ) {
+				startPlayback( getSlideDuration(), 0 );
+			}
+			if ( Reveal.isAutoSliding() ) {
+				var event = new CustomEvent('startplayback');
+				event.timestamp = 0;
+				document.dispatchEvent( event );
+			}
+			updateReadOnlyMode();			
+		}
+		else {
+			createPrintout();
+		}
+	});
+	Reveal.addEventListener( 'slidechanged', function( evt ) {
+//		clearTimeout( slidechangeTimeout );
+//console.log('slidechanged');
+		if ( !printMode ) {
+			slideStart = Date.now();
+			slideIndices = Reveal.getIndices();
+			closeChalkboard();				
+			clearCanvas( 0 );
+			clearCanvas( 1 );
+			if ( !playback ) {
+				slidechangeTimeout = setTimeout( startPlayback, transition, getSlideDuration(), 0 );
+			}
+			if ( Reveal.isAutoSliding() ) {
+				var event = new CustomEvent('startplayback');
+				event.timestamp = 0;
+				document.dispatchEvent( event );
+			}
+			
+			updateReadOnlyMode();			
+		}
+	});
+	Reveal.addEventListener( 'fragmentshown', function( evt ) {
+//		clearTimeout( slidechangeTimeout );
+//console.log('fragmentshown');
+		if ( !printMode ) {
+			slideStart = Date.now();		
+			slideIndices = Reveal.getIndices();		
+			closeChalkboard();				
+			clearCanvas( 0 );
+			clearCanvas( 1 );
+			if ( Reveal.isAutoSliding() ) {
+				var event = new CustomEvent('startplayback');
+				event.timestamp = 0;
+				document.dispatchEvent( event );
+			}				
+			else if ( !playback ) {
+				// 
+				startPlayback( getSlideDuration(), 0 );
+//				closeChalkboard();				
+			}
+			updateReadOnlyMode();			
+		}
+	});
+	Reveal.addEventListener( 'fragmenthidden', function( evt ) {
+//		clearTimeout( slidechangeTimeout );
+//console.log('fragmenthidden');
+		if ( !printMode ) {
+			slideStart = Date.now();		
+			slideIndices = Reveal.getIndices();		
+			closeChalkboard();				
+			clearCanvas( 0 );
+			clearCanvas( 1 );
+			if ( Reveal.isAutoSliding() ) {
+				document.dispatchEvent( new CustomEvent('stopplayback') );
+			}				
+			else if ( !playback ) {
+				startPlayback( getSlideDuration() );
+				closeChalkboard();				
+			}
+			updateReadOnlyMode();			
+		}
+	});
+
+	Reveal.addEventListener( 'autoslideresumed', function( evt ) {
+//console.log('autoslideresumed');
+		var event = new CustomEvent('startplayback');
+		event.timestamp = 0;
+		document.dispatchEvent( event );
+	});
+	Reveal.addEventListener( 'autoslidepaused', function( evt ) {
+//console.log('autoslidepaused');
+		document.dispatchEvent( new CustomEvent('stopplayback') );
+
+		// advance to end of slide
+//		closeChalkboard();				
+		startPlayback( getSlideDuration(), 0 );
+	});
+
+	function toggleNotesCanvas() {
+		if ( !readOnly ) {
+			if ( mode == 1 ) {
+				toggleChalkboard();
+				notescanvas.style.background = background[0]; //'rgba(255,0,0,0.5)';
+				notescanvas.style.pointerEvents = "auto";
+			}
+			else {
+				if ( notescanvas.style.pointerEvents != "none" ) {
+					event = null;
+					notescanvas.style.background = 'rgba(0,0,0,0)';
+					notescanvas.style.pointerEvents = "none";
+				}
+				else {
+					notescanvas.style.background = background[0]; //'rgba(255,0,0,0.5)';
+					notescanvas.style.pointerEvents = "auto";
+				}
+			}
+		}
+	};
+
+	function toggleChalkboard() {
+//console.log("toggleChalkboard " + mode);
+		if ( mode == 1 ) {
+			event = null;
+			if ( !readOnly ) recordEvent( { type:"close", begin: Date.now() - slideStart } );
+			closeChalkboard();
+		}
+		else {
+			showChalkboard();
+			if ( !readOnly ) recordEvent( { type:"open", begin: Date.now() - slideStart } );
+		}
+	};
+
+	function clear() {
+		if ( !readOnly ) {
+			recordEvent( { type:"clear", begin: Date.now() - slideStart } );
+			clearCanvas( mode );
+		}
+	};
+
+	function resetSlide( force ) {
+		var ok = force || confirm("Please confirm to delete chalkboard drawings on this slide!");
+		if ( ok ) {
+//console.log("resetSlide ");
+			stopPlayback();
+			slideStart = Date.now();			
+			event = null;
+			closeChalkboard();
+
+			clearCanvas( 0 );
+			clearCanvas( 1 );
+
+			mode = 1;
+			var slideData = getSlideData();	
+			slideData.duration = 0;
+			slideData.events = [];
+			mode = 0;
+			var slideData = getSlideData();	
+			slideData.duration = 0;
+			slideData.events = [];
+
+			updateReadOnlyMode();			
+		}
+	};
+
+	function resetStorage( force ) {
+		var ok = force || confirm("Please confirm to delete all chalkboard drawings!");
+		if ( ok ) {
+			stopPlayback();
+			slideStart = Date.now();
+			clearCanvas( 0 );
+			clearCanvas( 1 );
+			if ( mode == 1 ) {
+				event = null;
+				closeChalkboard();
+			}
+			storage = [
+					{ width: drawingCanvas[0].width - 2 * drawingCanvas[0].xOffset, height: drawingCanvas[0].height - 2 * drawingCanvas[0].yOffset, data: []},
+					{ width: drawingCanvas[1].width, height: drawingCanvas[1].height, data: []}
+				];
+
+			updateReadOnlyMode();			
+		}
+	};
+
+	this.drawWithPen = drawWithPen;
+	this.drawWithChalk = drawWithChalk;
+	this.toggleNotesCanvas = toggleNotesCanvas;
+	this.toggleChalkboard = toggleChalkboard;
+	this.startRecording = startRecording;
+	this.clear = clear;
+	this.reset = resetSlide;
+	this.resetAll = resetStorage;
+	this.download = downloadData;
+
+	return this;
+})();
diff --git a/inst/reveal.js-3.3.0/plugin/chalkboard/img/blackboard.png b/inst/reveal.js-3.3.0/plugin/chalkboard/img/blackboard.png
new file mode 100755
index 0000000..50a2f64
--- /dev/null
+++ b/inst/reveal.js-3.3.0/plugin/chalkboard/img/blackboard.png
Binary files differ
diff --git a/inst/reveal.js-3.3.0/plugin/chalkboard/img/boardmarker.png b/inst/reveal.js-3.3.0/plugin/chalkboard/img/boardmarker.png
new file mode 100755
index 0000000..7d1c5de
--- /dev/null
+++ b/inst/reveal.js-3.3.0/plugin/chalkboard/img/boardmarker.png
Binary files differ
diff --git a/inst/reveal.js-3.3.0/plugin/chalkboard/img/chalk.png b/inst/reveal.js-3.3.0/plugin/chalkboard/img/chalk.png
new file mode 100755
index 0000000..fed89a3
--- /dev/null
+++ b/inst/reveal.js-3.3.0/plugin/chalkboard/img/chalk.png
Binary files differ
diff --git a/inst/reveal.js-3.3.0/plugin/chalkboard/img/sponge.png b/inst/reveal.js-3.3.0/plugin/chalkboard/img/sponge.png
new file mode 100755
index 0000000..cbfb269
--- /dev/null
+++ b/inst/reveal.js-3.3.0/plugin/chalkboard/img/sponge.png
Binary files differ
diff --git a/inst/reveal.js-3.3.0/plugin/chalkboard/img/whiteboard.png b/inst/reveal.js-3.3.0/plugin/chalkboard/img/whiteboard.png
new file mode 100755
index 0000000..dbf570a
--- /dev/null
+++ b/inst/reveal.js-3.3.0/plugin/chalkboard/img/whiteboard.png
Binary files differ
diff --git a/inst/rmarkdown/templates/revealjs_presentation/resources/default.html b/inst/rmarkdown/templates/revealjs_presentation/resources/default.html
index 49bd060..c3fe016 100644
--- a/inst/rmarkdown/templates/revealjs_presentation/resources/default.html
+++ b/inst/rmarkdown/templates/revealjs_presentation/resources/default.html
@@ -283,6 +283,47 @@
         maxScale: $maxScale$,
 $endif$
 
+$if(plugin-chalkboard)$
+
+        chalkboard: {
+$if(chalkboard-src)$
+          src: $chalkboard-src$,
+$endif$
+$if(chalkboard-readOnly)$
+          readOnly: $chalkboard-readOnly$,
+$endif$
+$if(chalkboard-toggleNotesButton)$
+          toggleNotesButton: $chalkboard-toggleNotesButton$,
+$endif$
+$if(chalkboard-toggleChalkboardButton)$
+          toggleChalkboardButton: $chalkboard-toggleChalkboardButton$,
+$endif$
+$if(chalkboard-transition)$
+          transition: $chalkboard-transition$,
+$endif$
+$if(chalkboard-theme)$
+          theme: $chalkboard-theme$,
+$endif$
+$if(chalkboard-color)$
+          color: $chalkboard-color$,
+$endif$
+$if(chalkboard-background)$
+          background: $chalkboard-background$,
+$endif$
+$if(chalkboard-pen)$
+          pen: $chalkboard-pen$,
+$endif$
+        },
+
+        keyboard: {
+          67: function() { RevealChalkboard.toggleNotesCanvas() },    // toggle notes canvas when 'c' is pressed
+          66: function() { RevealChalkboard.toggleChalkboard() }, // toggle chalkboard when 'b' is pressed
+          46: function() { RevealChalkboard.clear() },    // clear chalkboard when 'DEL' is pressed
+           8: function() { RevealChalkboard.reset() },    // reset chalkboard data on current slide when 'BACKSPACE' is pressed
+          68: function() { RevealChalkboard.download() }, // downlad recorded chalkboard drawing when 'd' is pressed
+        },
+$endif$
+
         // Optional reveal.js plugins
         dependencies: [
 $if(plugin-notes)$
@@ -294,6 +335,9 @@
 $if(plugin-zoom)$
           { src: '$revealjs-url$/plugin/zoom-js/zoom.js', async: true },
 $endif$
+$if(plugin-chalkboard)$
+          { src: '$revealjs-url$/plugin/chalkboard/chalkboard.js', async: true },
+$endif$
         ]
       });
     </script>