<link href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="flex">
<a href="#">+</a>
<div class="modal">
<div class="inner-modal">
<div class="content">
<h1>Modal Content</h1>
<p>Pretty nifty.</p>
</div>
</div>
</div>
</div>
<script>
document.querySelector('a').addEventListener('click', function(e) {
e.preventDefault();
this.classList.toggle('opened');
});
</script>
