message: Add on-fullscreen mixin
diff: left: 50%;
  transform: translateX(-50%) translateY(-50%);
  }
  +@mixin on-fullscreen {
  + body.player-mode-webfullscreen &,
  + body.player-fullscreen-fix &,
  + body.player-full-win & {
  + @content;
  + }
  +}
  