html,
body {
  height: 100%;
}

body {
  display: flex;
  margin: 0;
}
#content {
  flex-grow: 1;
  background: steelblue;
  overflow-x: hidden;
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
}

#bgvid {
  object-fit: cover;
  width: 100%;
  height: 100%;
}


button {
  position:fixed;
  top:70%;
  left: 20%;
  display: block;
  width: 200px;
  padding: .4rem;
  border: none;
  margin: 1rem auto;
  font-size: 1.3rem;
  background: rgba(255,255,255,0.23);
  color: #fff;
  border-radius: 3px;
  cursor: pointer;
  -webkit-transition: .3s background;
  transition: .3s background;
}
button:hover {
  background: rgba(0,0,0,0.5);
}
