/* ---------- Video YouTube: ảnh bìa khi mở bằng file:// (js/59-xem-youtube.js) ---------- */
.yt-bia{position:relative;display:block;width:100%;aspect-ratio:16/9;background:#000;border-radius:12px;overflow:hidden;cursor:pointer}
.dv-video>.yt-bia{position:absolute;inset:0;height:100%;aspect-ratio:auto;border-radius:0}
.yt-bia>img{width:100%;height:100%;object-fit:cover;display:block;opacity:.85;transition:opacity .2s}
.yt-bia:hover>img{opacity:1}
.yt-play{position:absolute;left:50%;top:50%;width:72px;height:50px;transform:translate(-50%,-50%);background:#e62117;border-radius:14px;box-shadow:0 6px 18px rgba(0,0,0,.35)}
.yt-play::after{content:"";position:absolute;left:29px;top:15px;border-style:solid;border-width:10px 0 10px 17px;border-color:transparent transparent transparent #fff}
.yt-nhan{position:absolute;left:14px;bottom:12px;background:rgba(0,0,0,.7);color:#fff;font-size:13px;font-weight:600;padding:5px 12px;border-radius:999px}
.yt-ghichu{position:absolute;left:12px;right:12px;top:12px;background:#fff4e5;color:#8a5300;font-size:12px;line-height:1.45;padding:6px 10px;border-radius:8px;cursor:default}