.iframewrapper {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 */
    padding-top: 25px;
    height: 0;
    width: 100%;
}

    .iframewrapper iframe {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        border: none;
        height: 100vh;
    }

@media (max-width: 800px) {
    .iframewrapper {
        position: relative;
        padding-bottom: 56.25%; /* 16:9 */
        padding-top: 25px;
        height: 0;
        width: 100%;
    }

        .iframewrapper iframe {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border: none;
        }
}