body {
    background-color: #000;
}
h1 {
    color: #fff;
    margin-top: 30px;
}
iframe {
    width: 200px;
    height: 355px;
}
@media screen and (max-width : 450px) {    
    iframe {
        width: 350px;
        height: 621px;
        display: block;
        margin: auto;
    }
}