<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Popup Example</title>
    <style>
        /* Style for the overlay (popup background) */
        #popupOverlay {
            display: none; /* Hidden by default */
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            z-index: 1000;
        }

        /* Style for the popup itself */
        #popup {
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background-color: white;
            padding: 20px;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
            z-index: 1001;
            width: 300px;
            text-align: center;
        }

        /* Button to close the popup */
        #closeBtn {
            margin-top: 10px;
            padding: 5px 10px;
            background-color: red;
            color: white;
            border: none;
            cursor: pointer;
        }
    </style>
</head>
<body>

    <!-- Button to trigger popup -->
    <button id="showPopupBtn">Show Popup</button>

    <!-- Overlay for popup -->
    <div id="popupOverlay">
        <!-- Popup content -->
        <div id="popup">
            <h2>Popup Message</h2>
            <p>This is a simple popup example.</p>
            <button id="closeBtn">Close</button>
        </div>
    </div>

    <script>
        // Get elements
        const showPopupBtn = document.getElementById('showPopupBtn');
        const popupOverlay = document.getElementById('popupOverlay');
        const closeBtn = document.getElementById('closeBtn');

        // Show the popup when button is clicked
        showPopupBtn.addEventListener('click', function() {
            popupOverlay.style.display = 'block';
        });

        // Close the popup when close button is clicked
        closeBtn.addEventListener('click', function() {
            popupOverlay.style.display = 'none';
        });

        // Optionally close the popup if the user clicks outside of it
        window.addEventListener('click', function(event) {
            if (event.target === popupOverlay) {
                popupOverlay.style.display = 'none';
            }
        });
    </script>

</body>
</html>