#videoPlayer{
    display: block;
    margin-left: auto;
    margin-right: auto;
    width: 50%;
    border: 2px solid black;
    margin-bottom: 4em;
}
@media only screen and (max-width: 900px) {
    #videoPlayer{
        width: 100%;
        border: 0;
        height: 200px;
    }
}
@media only screen and (max-width: 900px){
    #video{
      margin-left: 3px;
      margin-right: 3px;
    }  
}