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HTML 

              
                <ul class="chat-thread">
	<li>Are we meeting today?</li>
	<li>yes, what time suits you?</li>
	<li>I was thinking after lunch, I have a meeting in the morning</li>
</ul>

<form class="chat-window">
	<input class="chat-window-message" name="chat-window-message" type="text" autocomplete="off" autofocus />
</form>
!

CSS 

              
                // Imports
// --------------------------------------
@import 'https://fonts.googleapis.com/css?family=Noto+Sans';

// Variables
// --------------------------------------
$scrollbar-width:              10px;
$chat-thread-bgd-color:        rgba(25,147,147,0.2);
$chat-thread-msg-arrow-size:   15px;
$chat-thread-avatar-size:      50px;
$chat-thread-offset:           #{$chat-thread-avatar-size + 30px};

body {
	padding: 0;
	margin: 0;
	background: -moz-linear-gradient(-45deg, #183850 0, #183850 25%, #192C46 50%, #22254C 75%, #22254C 100%);
	background: -webkit-linear-gradient(-45deg, #183850 0, #183850 25%, #192C46 50%, #22254C 75%, #22254C 100%);
	background-repeat: no-repeat;
  background-attachment: fixed;
}

::-webkit-scrollbar {
    width: $scrollbar-width;
}
 
::-webkit-scrollbar-track {
    border-radius: $scrollbar-width;
    background-color: rgba(25,147,147,0.1);
}
 
::-webkit-scrollbar-thumb {
     border-radius: $scrollbar-width;
    background-color: $chat-thread-bgd-color;
}

.chat-thread {
	margin: 24px auto 0 auto;
	padding: 0 20px 0 0;
	list-style: none;
	overflow-y: scroll;
  overflow-x: hidden;
}

.chat-thread li {
	position: relative;
	clear: both;
	display: inline-block;
	padding: 16px 40px 16px 20px;
	margin: 0 0 20px 0;
	font: 16px/20px 'Noto Sans', sans-serif;
	border-radius: 10px;
	background-color: $chat-thread-bgd-color;
}

/* Chat - Avatar */
.chat-thread li:before {
	position: absolute;
	top: 0;
	width: $chat-thread-avatar-size;
	height: $chat-thread-avatar-size;
	border-radius: $chat-thread-avatar-size;
	content: '';
}

/* Chat - Speech Bubble Arrow */
.chat-thread li:after {
	position: absolute;
  top: $chat-thread-msg-arrow-size;
	content: '';
	width: 0;
	height: 0;
	border-top: $chat-thread-msg-arrow-size solid $chat-thread-bgd-color;
}

.chat-thread li:nth-child(odd) {
	animation: show-chat-odd 0.15s 1 ease-in;
	-moz-animation: show-chat-odd 0.15s 1 ease-in;
	-webkit-animation: show-chat-odd 0.15s 1 ease-in;
	float: right;
	margin-right: $chat-thread-offset;
	color: #0AD5C1;
}

.chat-thread li:nth-child(odd):before {
	right: -$chat-thread-offset;
  // Placeholder avatar 1
	background-image: url(data:image/jpeg;base64,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);
}

.chat-thread li:nth-child(odd):after {
	border-right: $chat-thread-msg-arrow-size solid transparent;
	right: -$chat-thread-msg-arrow-size;
}

.chat-thread li:nth-child(even) {
	animation: show-chat-even 0.15s 1 ease-in;
	-moz-animation: show-chat-even 0.15s 1 ease-in;
	-webkit-animation: show-chat-even 0.15s 1 ease-in;
	float: left;
	margin-left: $chat-thread-offset;
	color: #0EC879;
}

.chat-thread li:nth-child(even):before {
	left: -$chat-thread-offset;
  // Placeholder avatar 2
	background-image: url(data:image/jpeg;base64,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);
}

.chat-thread li:nth-child(even):after {
	border-left: $chat-thread-msg-arrow-size solid transparent;
	left: -$chat-thread-msg-arrow-size;
}

.chat-window {
	position: fixed;
	bottom: 18px;
}

.chat-window-message {
	width: 100%;
	height: 48px;
	font: 32px/48px 'Noto Sans', sans-serif;
	background: none;
	color: #0AD5C1;
	border: 0;
	border-bottom: 1px solid $chat-thread-bgd-color;
	outline: none;
}

// A tiny bit responsive...
// --------------------------------------
/* Small screens */
@media all and (max-width: 767px) {
	.chat-thread {
		width: 90%;
		height: 260px;
	}

	.chat-window {
		left: 5%;
		width: 90%;
	}
}

/* Medium and large screens */
@media all and (min-width: 768px) {
	.chat-thread {
		width: 50%;
		height: 320px;
	}

	.chat-window {
		left: 25%;
		width: 50%;
	}
}

// Animation
// --------------------------------------
@keyframes show-chat-even {
  0% {
    margin-left: -480px;
  }
  100% {
    margin-left: 0;
  }
}

@-moz-keyframes show-chat-even {
  0% {
    margin-left: -480px;
  }
  100% {
    margin-left: 0;
  }
}

@-webkit-keyframes show-chat-even {
  0% {
    margin-left: -480px;
  }
  100% {
    margin-left: 0;
  }
}

@keyframes show-chat-odd {
  0% {
    margin-right: -480px;
  }
  100% {
    margin-right: 0;
  }
}

@-moz-keyframes show-chat-odd {
  0% {
    margin-right: -480px;
  }
  100% {
    margin-right: 0;
  }
}

@-webkit-keyframes show-chat-odd {
  0% {
    margin-right: -480px;
  }
  100% {
    margin-right: 0;
  }
}
!

JS 

              
                // Chat (WebRTC)
//
// Currently supported in Chrome and Firefox only.
// WebRTC support is ultra basic at the moment - send/receive // in current window only.
// Design based on Bookmarks app by // Eyal Zuri - http://dribbble.com/shots/1261465-Bookmarks-app-gif
//
// The below JS has been adapted from this excellent RTCDataChannel demo
// http://simpl.info/rtcdatachannel/

var sendChannel, 
	receiveChannel,
	chatWindow = document.querySelector('.chat-window'),
	chatWindowMessage = document.querySelector('.chat-window-message'),
	chatThread = document.querySelector('.chat-thread');

// Create WebRTC connection
createConnection();

// On form submit, send message
chatWindow.onsubmit = function (e) {
	e.preventDefault();

	sendData();

	return false;
};

function createConnection () {
    var servers = null;

    if (window.mozRTCPeerConnection) {
	    window.localPeerConnection = new mozRTCPeerConnection(servers, {
	        optional: [{
	            RtpDataChannels: true
	        }]
	    });
    } else {
	    window.localPeerConnection = new webkitRTCPeerConnection(servers, {
	        optional: [{
	            RtpDataChannels: true
	        }]
	    });
    }

    try {
        // Reliable Data Channels not yet supported in Chrome
        sendChannel = localPeerConnection.createDataChannel('sendDataChannel', {
            reliable: false
        });
    } catch (e) {
    }

    localPeerConnection.onicecandidate = gotLocalCandidate;
    sendChannel.onopen = handleSendChannelStateChange;
    sendChannel.onclose = handleSendChannelStateChange;

    if (window.mozRTCPeerConnection) {
	    window.remotePeerConnection = new mozRTCPeerConnection(servers, {
	        optional: [{
	            RtpDataChannels: true
	        }]
	    });
    } else {
	    window.remotePeerConnection = new webkitRTCPeerConnection(servers, {
	        optional: [{
	            RtpDataChannels: true
	        }]
	    });
    }

    remotePeerConnection.onicecandidate = gotRemoteIceCandidate;
    remotePeerConnection.ondatachannel = gotReceiveChannel;

    // Firefox seems to require an error callback
    localPeerConnection.createOffer(gotLocalDescription, function (err) {
    });
}

function sendData () {
    sendChannel.send(chatWindowMessage.value);
}

function gotLocalDescription (desc) {
    localPeerConnection.setLocalDescription(desc);
    remotePeerConnection.setRemoteDescription(desc);
    // Firefox seems to require an error callback
    remotePeerConnection.createAnswer(gotRemoteDescription, function (err) {
    });
}

function gotRemoteDescription (desc) {
    remotePeerConnection.setLocalDescription(desc);
    localPeerConnection.setRemoteDescription(desc);
}

function gotLocalCandidate (event) {
    if (event.candidate) {
        remotePeerConnection.addIceCandidate(event.candidate);
    }
}

function gotRemoteIceCandidate (event) {
    if (event.candidate) {
        localPeerConnection.addIceCandidate(event.candidate);
    }
}

function gotReceiveChannel (event) {
    receiveChannel = event.channel;
    receiveChannel.onmessage = handleMessage;
    receiveChannel.onopen = handleReceiveChannelStateChange;
    receiveChannel.onclose = handleReceiveChannelStateChange;
}

function handleMessage (event) {
    var chatNewThread = document.createElement('li'),
    	chatNewMessage = document.createTextNode(event.data);

    // Add message to chat thread and scroll to bottom
    chatNewThread.appendChild(chatNewMessage);
    chatThread.appendChild(chatNewThread);
    chatThread.scrollTop = chatThread.scrollHeight;

    // Clear text value
    chatWindowMessage.value = '';
}

function handleSendChannelStateChange () {
    var readyState = sendChannel.readyState;

    if (readyState == 'open') {
        chatWindowMessage.disabled = false;
        chatWindowMessage.focus();
    	chatWindowMessage.placeholder = "";
    } else {
        chatWindowMessage.disabled = true;
    }
}

function handleReceiveChannelStateChange () {
    var readyState = receiveChannel.readyState;
}
!
999px

Console