*,*::before,*::after{box-sizing:border-box}
:root{
  --paper:#faf6ee; --paper2:#f4eee2; --card:#fffdf8;
  --ink:#2a241c; --ink2:#4a4136; --mute:#8a7c68; --faint:#b3a795;
  --rule:#e4d9c6; --accent:#8b5e34; --accent2:#a97544; --seal:#9c3b2e;
}
html{scroll-behavior:smooth}
body{
  margin:0;background:var(--paper);color:var(--ink);
  font-family:"Source Han Serif SC","Noto Serif SC","Songti SC",Georgia,"PingFang SC","Microsoft YaHei",serif;
  line-height:1.85;-webkit-font-smoothing:antialiased;
}
a{color:var(--accent);text-decoration:none}
a:hover{color:var(--seal)}
.wrap{width:min(880px,92vw);margin:0 auto}
.wrap-wide{width:min(1180px,92vw);margin:0 auto}

/* 顶栏：与作品集保持同一品牌，但用浅色 */
header{position:sticky;top:0;z-index:40;background:rgba(250,246,238,.92);
  backdrop-filter:blur(10px);border-bottom:1px solid var(--rule)}
.bar{display:flex;align-items:center;justify-content:space-between;height:60px;
  font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif}
.brand{display:flex;align-items:center;gap:10px;font-weight:700;font-size:15px;color:var(--ink)}
.brand .mark{width:28px;height:28px;border-radius:8px;display:grid;place-items:center;
  font-size:14px;background:linear-gradient(135deg,var(--accent),var(--accent2));color:#fff}
.bar nav{display:flex;gap:22px;font-size:13.5px}
.bar nav a{color:var(--ink2)}
.bar nav a:hover{color:var(--seal)}

/* 讲义页头 */
.head{padding:38px 0 26px;border-bottom:1px solid var(--rule)}
.crumb{font-size:12.5px;color:var(--mute);margin-bottom:14px;
  font-family:-apple-system,"PingFang SC",sans-serif}
.crumb a{color:var(--mute)}
.crumb a:hover{color:var(--seal)}
h1{margin:0 0 14px;font-size:clamp(24px,4vw,34px);line-height:1.35;font-weight:700;letter-spacing:.01em}
.meta{display:flex;flex-wrap:wrap;gap:8px 18px;font-size:13px;color:var(--mute);
  font-family:-apple-system,"PingFang SC",sans-serif}
.meta b{color:var(--accent);font-weight:600}

/* 一句话答案：GEO 抓手，AI 最爱摘这段 */
.answer{margin:26px 0 0;padding:18px 22px;background:var(--paper2);
  border-left:4px solid var(--accent);border-radius:0 10px 10px 0;font-size:15px;color:var(--ink2)}
.answer .lb{display:block;font-size:11.5px;letter-spacing:.12em;color:var(--accent);
  margin-bottom:7px;font-family:-apple-system,"PingFang SC",sans-serif;font-weight:600}

/* 播放器 */
.player{margin:30px 0 0;border-radius:12px;overflow:hidden;background:#000;
  box-shadow:0 14px 38px -18px rgba(42,36,28,.5)}
.player video{width:100%;display:block;aspect-ratio:16/9}
.gate{margin:30px 0 0;padding:30px 26px;background:var(--card);border:1px solid var(--rule);
  border-radius:12px;text-align:center}
.gate h3{margin:0 0 8px;font-size:17px}
.gate p{margin:0 0 18px;color:var(--mute);font-size:13.5px;
  font-family:-apple-system,"PingFang SC",sans-serif}
.gate .btn{display:inline-block;padding:11px 26px;border-radius:9px;font-size:14px;font-weight:600;
  background:var(--accent);color:#fff;font-family:-apple-system,"PingFang SC",sans-serif;
  cursor:pointer;border:0}
.gate .btn:hover{background:var(--seal);color:#fff}

/* 讲堂索引页底部的留资区 */
.cta{margin:56px 0 10px;padding:34px 30px;background:var(--card);border:1px solid var(--rule);
  border-radius:14px;text-align:center}
.cta h2{margin:0 0 10px;font-size:20px}
.cta p{margin:0 auto;max-width:620px;color:var(--mute);font-size:14px;line-height:1.75;
  font-family:-apple-system,"PingFang SC",sans-serif}
.ctabtns{margin:22px 0 0;display:flex;gap:12px;justify-content:center;flex-wrap:wrap}
.btn{display:inline-block;padding:12px 28px;border-radius:9px;font-size:14.5px;font-weight:600;
  background:var(--accent);color:#fff;border:0;cursor:pointer;
  font-family:-apple-system,"PingFang SC",sans-serif}
.btn:hover{background:var(--seal);color:#fff}
.btn.ghost{background:transparent;color:var(--accent);border:1px solid var(--rule)}
.btn.ghost:hover{background:var(--card);color:var(--seal)}
.ctanote{margin:18px 0 0;font-size:12px;color:var(--mute);
  font-family:-apple-system,"PingFang SC",sans-serif}

/* 目次 */
.toc{margin:34px 0 0;padding:20px 24px;background:var(--card);
  border:1px solid var(--rule);border-radius:12px}
.toc h2{margin:0 0 12px;font-size:14px;color:var(--accent);letter-spacing:.06em;
  font-family:-apple-system,"PingFang SC",sans-serif}
.toc ol{margin:0;padding:0;list-style:none;columns:2;column-gap:30px;font-size:13.5px;
  font-family:-apple-system,"PingFang SC",sans-serif}
.toc li{margin:0 0 5px;break-inside:avoid;color:var(--ink2)}
.toc li a{color:var(--ink2)}
.toc li a:hover{color:var(--seal)}

/* 讲义正文 */
article{padding:14px 0 60px}
.sec{padding:34px 0 6px;border-top:1px solid var(--rule);margin-top:34px}
.sec:first-child{border-top:0;margin-top:8px}
.sec .no{font-size:12px;letter-spacing:.14em;color:var(--faint);margin-bottom:8px;
  font-family:-apple-system,"PingFang SC",sans-serif}
.sec h2{margin:0 0 16px;font-size:21px;line-height:1.5;font-weight:700;color:var(--ink)}
.pts{margin:0 0 20px;padding:0;list-style:none;font-size:14px;color:var(--ink2)}
.pts li{position:relative;padding-left:16px;margin-bottom:6px;line-height:1.75}
.pts li::before{content:"";position:absolute;left:0;top:.72em;width:5px;height:5px;
  border-radius:50%;background:var(--accent2)}
.note{margin:0 0 16px;font-size:15.5px;line-height:1.95;text-align:justify}
.note-tag{display:inline-block;margin-right:8px;padding:1px 9px;border-radius:5px;
  font-size:12px;vertical-align:1px;letter-spacing:.05em;
  font-family:-apple-system,"PingFang SC",sans-serif;font-weight:600}
.tag-j{background:rgba(139,94,52,.1);color:var(--accent)}
.tag-g{background:rgba(156,59,46,.09);color:var(--seal)}
.tag-h{background:rgba(70,110,90,.11);color:#3f6b55}

/* 相关 */
.rel{margin:44px 0 0;padding:24px 0 0;border-top:1px solid var(--rule)}
.rel h2{font-size:15px;margin:0 0 14px;color:var(--accent);letter-spacing:.06em;
  font-family:-apple-system,"PingFang SC",sans-serif}
.rel .list{display:flex;flex-wrap:wrap;gap:9px}
.rel .list a{padding:7px 14px;background:var(--card);border:1px solid var(--rule);
  border-radius:20px;font-size:13px;color:var(--ink2);
  font-family:-apple-system,"PingFang SC",sans-serif}
.rel .list a:hover{border-color:var(--accent);color:var(--seal)}

footer{margin-top:20px;padding:30px 0 44px;border-top:1px solid var(--rule);
  text-align:center;color:var(--mute);font-size:12.5px;
  font-family:-apple-system,"PingFang SC",sans-serif}
footer a{color:var(--mute);border-bottom:1px dashed var(--faint)}

/* ---------- 索引页 ---------- */
.ihead{padding:46px 0 30px;text-align:center}
.ihead h1{font-size:clamp(26px,4.6vw,38px);margin-bottom:12px}
.ihead p{margin:0 auto;max-width:640px;color:var(--mute);font-size:14.5px}
.istats{display:flex;justify-content:center;gap:clamp(22px,5vw,52px);margin:26px 0 0;flex-wrap:wrap}
.istats div b{display:block;font-size:23px;font-weight:700;color:var(--accent)}
.istats div span{font-size:12px;color:var(--mute);
  font-family:-apple-system,"PingFang SC",sans-serif;letter-spacing:.06em}
.tools{display:flex;flex-wrap:wrap;gap:12px;align-items:center;justify-content:center;
  margin:32px 0 26px;font-family:-apple-system,"PingFang SC",sans-serif}
.tools input{flex:1 1 240px;max-width:320px;padding:10px 15px;font-size:14px;
  border:1px solid var(--rule);border-radius:9px;background:var(--card);color:var(--ink);outline:none}
.tools input:focus{border-color:var(--accent)}
.chips{display:flex;flex-wrap:wrap;gap:7px;justify-content:center}
.chips button{padding:6px 15px;font-size:13px;border-radius:18px;cursor:pointer;
  border:1px solid var(--rule);background:var(--card);color:var(--ink2);transition:all .18s}
.chips button:hover{border-color:var(--accent2)}
.chips button.on{background:var(--accent);border-color:var(--accent);color:#fff}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(268px,1fr));gap:18px;
  padding-bottom:20px}
.lcard{display:flex;flex-direction:column;background:var(--card);border:1px solid var(--rule);
  border-radius:12px;overflow:hidden;transition:transform .2s,box-shadow .2s,border-color .2s}
.lcard:hover{transform:translateY(-4px);border-color:var(--accent2);
  box-shadow:0 16px 34px -20px rgba(42,36,28,.45)}
.lcard .thumb{position:relative;aspect-ratio:16/9;background:var(--paper2);overflow:hidden}
.lcard .thumb img{width:100%;height:100%;object-fit:cover;display:block}
.lcard .thumb .free{position:absolute;top:9px;left:9px;padding:2px 9px;border-radius:5px;
  font-size:11px;font-weight:600;background:var(--seal);color:#fff;
  font-family:-apple-system,"PingFang SC",sans-serif}
.lcard .bd{padding:14px 16px 16px;flex:1;display:flex;flex-direction:column}
.lcard h3{margin:0 0 5px;font-size:16px;line-height:1.45}
.lcard .sub{font-size:11.5px;color:var(--faint);letter-spacing:.08em;margin-bottom:9px;
  font-family:-apple-system,"PingFang SC",sans-serif}
.lcard .nums{margin-top:auto;padding-top:10px;font-size:12px;color:var(--mute);
  font-family:-apple-system,"PingFang SC",sans-serif;display:flex;gap:14px}
.empty{text-align:center;padding:50px 0;color:var(--mute);font-size:14px;
  font-family:-apple-system,"PingFang SC",sans-serif}

@media(max-width:760px){
  .toc ol{columns:1}
  .bar nav{display:none}
  .grid{grid-template-columns:1fr}
  .note{font-size:15px;text-align:left}
}