.book-video{position:relative;width:100%;aspect-ratio:16/9;min-height:200px;background:#fff9dd;border-radius:12px;overflow:hidden}
.book-video-poster{position:absolute;inset:0;display:block;width:100%;height:100%;object-fit:contain}
.book-video iframe{position:relative;z-index:1;display:block;width:100%;height:100%;min-height:200px;border:0}
.book-video-status{margin:8px 0;color:var(--muted)}
.book-video-status[hidden],.book-video-help[hidden]{display:none}
.book-video-help{margin:8px 0;line-height:1.5}
.book-video-help a{color:var(--rose);font-weight:700}
.video-book-title{font-size:23px;line-height:1.25;margin:16px 0}
.sheet-body>.book-more{margin:18px 0}
.book-more-content>.detail-image{width:100%;max-height:320px;object-fit:contain;margin:0 0 16px}
.book-more>summary{min-height:44px;display:flex;align-items:center;gap:8px;cursor:pointer}
.book-more>summary::before{content:'+';font-size:22px;font-weight:700;flex:none}
.book-more[open]>summary::before{content:'−'}