body {
    padding: 20px;

a {
    color: black;
}

@media screen and (orientation:portrait) {

    #mainbody {
        height: 100vw;
    }

    .video {
        position: relative;
        width: 100%;
        height: auto;
    }
}

@media screen and (orientation:landscape) {

    #mainbody {
        -webkit-transform: rotate(0deg);
        -moz-transform: rotate(0deg);
        -o-transform: rotate(0deg);
        -ms-transform: rotate(0deg);
        transform: rotate(0deg);
    }
}