.video {
    background-color: #e6e6e6;
    position: relative;
    width: 100%;
    padding-bottom: 66.667%; /* 0.66667 aspect ratio */
    height: 0;
    overflow: hidden;
 }

.video video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}