YouTube - Turn Off the Lights by nuguri

/* ==UserStyle==
@name           YouTube - Turn Off the Lights
@namespace      youtube.com
@description    Turn off the lights in youtube using only css
@version        1.0.0
@author         Me
==/UserStyle== */

@-moz-document url-prefix("https://www.youtube.com/watch?v=") {

        iron-a11y-announcer {
         display: unset;
         position: unset;
         clip: unset;
        }

        div.style-scope.iron-a11y-announcer {
         width: 100%;
         height: 100%;
         left: 0px;
         top: 0px;
         position: fixed;
         background: rgb(0, 0, 0) none repeat scroll 0% 0%;
         opacity: 0.9;
         z-index: 999;
        }

        #masthead-container.ytd-app {
         z-index: unset;
        }

        #player-container,
        #player.ytd-watch-flexy {
         z-index: 9999;
        }

}