Youtube custom CSS

youtube.css

#masthead-container {
    position: unset;
}

#page-manager.ytd-app {
    margin-top: 0;
}

ytd-watch-flexy[theater] #player-theater-container.ytd-watch-flexy, ytd-watch-flexy[fullscreen] #player-theater-container.ytd-watch-flexy {
    max-height: calc( 100vh - 20px ) ;
}

#container.ytd-masthead {
    height: 20px;
}