html, body {
        margin: 0;
        padding: 0;
        height: 100%;
        overflow: hidden; /* Prevent scrollbars on the main page */
    }

    #fullscreenIframe {
        position: fixed; /* Position relative to the viewport */
        top: 0;
        left: 0;
        width: 100vw; /* 100% of viewport width */
        height: 100vh; /* 100% of viewport height */
        border: none; /* Remove default iframe border */
        z-index: 9999; /* Ensure it's on top of other content if needed */
    }