YouTubeのウィンドウを小さくした時に邪魔な要素を隠すやつ

youtube-mini-player.user.css

/* ==UserStyle==
@name           youtube - Mini Player
@namespace      github.com/unarist
@version        1.0.0
@author         unarist
==/UserStyle== */

@-moz-document url-prefix("https://www.youtube.com/watch?") {
    @media (max-width: 800px) and (max-height: 500px) {
        /* show topbar only when hovered */
        #masthead-container { transition-property: all !important }
        html:not(:hover) #masthead-container { opacity: 0 }
        
        /* full video */
        #page-manager { margin: 0 !important }
        .html5-main-video {
            width: 100vw !important;
            height: 100vh !important;
            top: unset !important;
        }
        .ytp-gradient-bottom, .ytp-chrome-bottom { position: fixed; bottom: 0; }
        
        /* hide scrollbar */
        ::-webkit-scrollbar { width: 0 !important; }
    }
}