html,body { margin:0; width:100%; height:100%; overflow:hidden; background:#171719; color:#fff; font-family:Arial,sans-serif; }
#stage { position:absolute; top:0; right:0; bottom:0; left:0; }
#stage img,#stage video { position:absolute; top:0; left:0; width:100%; height:100%; object-fit:contain; }
#a { visibility:visible; }
#b,#video { visibility:hidden; }
#diagnostic { position:absolute; left:50%; top:50%; transform:translate(-50%,-50%); box-sizing:border-box; width:74%; max-width:620px; max-height:40%; overflow:auto; padding:16px; border:1px solid rgba(255,255,255,.5); border-radius:12px; background:rgba(23,23,25,.92); text-align:center; font-size:20px; font-size:2.4vmin; line-height:1.35; }
#diagnostic p { margin:.5em 0 0; }
#message { color:#ffe8af; }
noscript { position:absolute; top:42%; left:15%; right:15%; padding:20px; color:white; background:#94282f; }