echo '<style>
/* The Modal (background) */
p {
color:black;
}
.modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1000; /* Sit on top */
    padding-top: 100px; /* Location of the box */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    overflow: auto; /* Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
}

/* Modal Content */
.modal-content {
    background-color: #fefefe;
    margin: auto;
    padding: 20px;
    border: 1px solid #888;
    width: 50%;
}

/* The Close Button */
.close {
    color: #aaaaaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
}

.close:hover,
.close:focus {
    color: #000;
    text-decoration: none;
    cursor: pointer;
}
</style>';

// modal window

echo '<div id="myModal" class="modal">
<div class="modal-content">
  <span class="close">&times;</span>
  <p>Correct answer</p>
</div>
</div>';

// manage opening and closing:
echo '<script>
    jQuery(document).ready(function() {
    var modal = document.getElementById("myModal");
    var btn = document.getElementById("myBtn");
    var span = document.getElementsByClassName("close")[0];

span.onclick = function() {
    modal.style.display = "none";
}
window.onclick = function(event) {
    if (event.target == modal) {
        modal.style.display = "none";
    }
}