style.css

body {
  margin: 0px;
  padding: 0px;
  background: #000;
}

#vid_container {
  position: fixed;
  top: 0;
  left: 0;
}

#video {
  width: 100%;
  height: 100%;
  object-fit: cover;
  z-index: 0;
}

#gui_controls {
  position: fixed;
  background-color: #111; /*rgba(255, 0, 0, 0.5);*/
  z-index: 2;
  bottom: 0;
}

#video_overlay {
  position: fixed;
  display: none;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;

  z-index: 10;
  background-color: #111;
}

/*  Button style from: 
    https://googlesamples.github.io/web-fundamentals/fundamentals/media/mobile-web-video-playback.html */

button {
  outline: none;
  position: absolute;
  color: white;
  display: block;
  opacity: 1;
  background: transparent;
  border: solid 2px #fff;
  padding: 0;
  text-shadow: 0px 0px 4px black;
  background-position: center center;
  background-repeat: no-repeat;
  pointer-events: auto;
  z-index: 2;
}

#takePhotoButton {
  left: calc(50% - 40px);
  top: calc(50% - 40px);
  width: 80px;
  height: 80px;
  background-image: url('img/ic_photo_camera_white_48px.svg');
  border-radius: 50%;
  background-color: rgba(0, 0, 0, 0.5);
}

#takePhotoButton:active {
  background-color: #fff;
}

#toggleFullScreenButton {
  display: none;
  width: 64px;
  height: 64px;
  background-image: url('img/ic_fullscreen_white_48px.svg');
  border-radius: 50%;
  background-color: rgba(0, 0, 0, 0.5);
}

#toggleFullScreenButton[aria-pressed='true'] {
  background-image: url('img/ic_fullscreen_exit_white_48px.svg');
}

#switchCameraButton {
  display: none;
  width: 64px;
  height: 64px;
  background-image: url('img/ic_camera_rear_white_36px.svg');
  border-radius: 50%;
  background-color: rgba(0, 0, 0, 0.5);
}

#switchCameraButton[aria-pressed='true'] {
  background-image: url('img/ic_camera_front_white_36px.svg');
}

@media screen and (orientation: portrait) {
  /* portrait-specific styles */

  /* video_container (video) doesn't respect height... 
       so we will fill it in completely in portrait mode
    */
  #vid_container {
    width: 100%;
    height: 80%;
  }

  #gui_controls {
    width: 100%;
    height: 20%;
    left: 0;
  }

  #switchCameraButton {
    left: calc(20% - 32px);
    top: calc(50% - 32px);
  }

  #toggleFullScreenButton {
    left: calc(80% - 32px);
    top: calc(50% - 32px);
  }
}

@media screen and (orientation: landscape) {
  #vid_container {
    width: 80%;
    height: 100%;
  }

  #vid_container.left {
    left: 20%;
  }

  /* we default to right */
  #gui_controls {
    width: 20%;
    height: 100%;
    right: 0;
  }

  /* for the lefties */
  #gui_controls.left {
    left: 0;
  }

  #switchCameraButton {
    left: calc(50% - 32px);
    top: calc(18% - 32px);
  }

  #toggleFullScreenButton {
    left: calc(50% - 32px);
    top: calc(82% - 32px);
  }
}