<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<style>
body {
font-family: Arial;
}
* {
box-sizing: border-box;
}
.openBtn {
background: #f1f1f1;
border: none;
padding: 10px 15px;
font-size: 20px;
cursor: pointer;
}
.openBtn:hover {
background: #bbb;
}
.overlay {
height: 100%;
width: 100%;
display: none;
position: fixed;
z-index: 1;
top: 0;
