/* Optional: make iframe responsive */
        .flipbook-container {
            position: relative;
            padding-bottom: 70%; /* Adjust height ratio */
            height: 500 px;
            overflow: hidden;
        }
        .flipbook-container iframe {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border: none;
        }