html,body {
   height: 100%;
   margin: 0;
 }
body {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background-color: #171717;
    font: normal 1em / 1.5  arial, helvetica, sans-serif;
    color: #fff;
 }
h1 {
   font-size: 1.5em;
   font-weight: normal;
 }
video {
   display: block;
   width: 100%;
   max-width: 40em;
 }