/* ==========================================================================
   知识课堂 — 目录页 /learn 与文章页 /learn/<slug> 共用样式
   ========================================================================== */

/* ---------------- 目录页：页头横幅 ---------------- */

.learn-hero { margin: 24px 0 0; }
.learn-hero .lh-cover {
  width: 100%; height: auto;
  display: block;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
}

.learn-intro { max-width: 800px; margin: 28px auto 0; text-align: center; }
.learn-intro h1 {
  font-family: var(--font-display);
  font-size: clamp(26px, 4vw, 40px); line-height: 1.22;
  margin: 8px 0 12px;
}
.learn-intro .lede { color: var(--text-2); font-size: 16px; line-height: 1.85; margin: 0 auto; max-width: 62ch; }

/* ---------------- 目录卡片网格 ---------------- */

.lesson-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 18px; margin-top: 22px;
}
.lesson-card {
  display: flex; flex-direction: column;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); overflow: hidden; color: inherit;
  text-decoration: none;
  transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.lesson-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg, 0 12px 32px rgba(26,46,61,.10));
  border-color: var(--accent);
}
.lesson-card .lc-img { position: relative; aspect-ratio: 4 / 3; overflow: hidden; background: var(--surface-2); }
.lesson-card .lc-img img {
  width: 100%; height: 100%; object-fit: cover; display: block;
  transition: transform .55s var(--ease);
}
.lesson-card:hover .lc-img img { transform: scale(1.045); }
.lesson-card .lc-no {
  position: absolute; top: 10px; left: 10px;
  width: 30px; height: 30px; border-radius: 50%;
  display: grid; place-items: center;
  background: rgba(255,254,251,.94); color: var(--accent);
  font-family: var(--mono); font-size: 12.5px; font-weight: 700;
  border: 1px solid var(--accent-line, rgba(184,50,39,.25));
}
.lesson-card .lc-body { padding: 15px 17px 16px; display: flex; flex-direction: column; flex: 1 1 auto; }
.lesson-card .lc-tag {
  font-size: 11.5px; letter-spacing: .08em; text-transform: uppercase;
  color: var(--accent); margin-bottom: 7px;
}
.lesson-card .lc-title {
  font-family: var(--font-display); font-size: 16.5px; font-weight: 700;
  line-height: 1.45; margin-bottom: 8px;
}
.lesson-card .lc-hook { font-size: 13px; color: var(--text-3); line-height: 1.65; flex: 1 1 auto; }
.lesson-card .lc-foot {
  display: flex; align-items: center; justify-content: space-between;
  margin-top: 13px; font-size: 12px; color: var(--text-3);
}
.lesson-card .lc-read { color: var(--accent); font-weight: 600; }

.learn-disclaimer {
  margin-top: 34px; padding-top: 18px;
  border-top: 1px solid var(--border);
  max-width: 780px;
}

/* ---------------- 文章页 ---------------- */

.article-head { margin: 28px 0 24px; }
.article-head .ah-back {
  display: inline-flex; align-items: center; gap: 6px;
  min-height: 48px; font-size: 12.8px; color: var(--text-2); text-decoration: none;
}
.article-head .ah-back:hover { color: var(--accent); }
.article-head .ah-tag {
  display: block; margin-top: 6px;
  font-size: 12px; letter-spacing: .1em; text-transform: uppercase; color: var(--accent);
}
.article-head h1 {
  font-family: var(--font-display);
  font-size: clamp(24px, 3.6vw, 36px); line-height: 1.26;
  margin: 8px 0 12px;
}
.article-head .ah-hook { font-size: 16.5px; color: var(--text-2); line-height: 1.7; margin: 0; }
.article-head .ah-meta { margin-top: 12px; font-size: 12.5px; color: var(--text-3); }

/* 场景导入 */
.lede-block {
  padding: 16px 19px; margin-bottom: 28px;
  border-left: 3px solid var(--accent);
  background: var(--surface-2);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: 14.8px; line-height: 1.9; color: var(--text);
}

/* 知识点 */
.sec-block { margin-bottom: 26px; }
.sec-block h2 {
  font-family: var(--font-display); font-size: 18px; font-weight: 700;
  margin: 0 0 9px;
}
.sec-block p { font-size: 14.8px; line-height: 1.92; color: var(--text-2); margin: 0; }

/* 插图 */
.article-fig { margin: 28px 0; text-align: center; }
.article-fig img {
  width: 100%; max-width: 760px; height: auto; display: block; margin: 0 auto;
  border-radius: var(--radius); border: 1px solid var(--border);
  background: var(--surface-2);
}
.article-fig figcaption { margin-top: 9px; font-size: 12.3px; color: var(--text-3); line-height: 1.6; }

/* 案例 */
.case-block { margin: 30px 0; border-left: 3px solid var(--accent); }
.case-block .cb-label {
  display: inline-block; margin-bottom: 7px;
  font-size: 11px; letter-spacing: .1em; text-transform: uppercase; color: var(--accent);
}
.case-block p { font-size: 14.6px; line-height: 1.9; color: var(--text-2); margin: 0; }

/* 功能引导 */
.article-cta {
  margin: 34px 0; padding: 20px 22px;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface-2);
}
.article-cta h3 { font-family: var(--font-display); font-size: 16.5px; margin: 0 0 8px; }
.article-cta p { font-size: 13.8px; color: var(--text-2); line-height: 1.82; margin: 0 0 15px; }
.article-cta .btns { display: flex; gap: 11px; flex-wrap: wrap; }

/* 上一篇 / 下一篇 */
.lesson-nav {
  display: flex; align-items: stretch; justify-content: space-between; gap: 14px;
  margin-top: 34px; padding-top: 22px; border-top: 1px solid var(--border);
}
.lesson-nav a {
  display: flex; flex-direction: column; gap: 4px; justify-content: center;
  min-height: 48px; max-width: 48%; text-decoration: none; color: inherit;
}
.lesson-nav .ln-k { font-size: 11.5px; letter-spacing: .08em; text-transform: uppercase; color: var(--text-3); }
.lesson-nav .ln-t { font-size: 13.6px; font-weight: 600; line-height: 1.5; }
.lesson-nav a:hover .ln-t { color: var(--accent); }
.lesson-nav .ln-next { margin-left: auto; text-align: right; }

.article-footnote {
  margin-top: 30px; padding-top: 18px; border-top: 1px solid var(--border);
}

/* ---------------- 响应式 ---------------- */

@media (max-width: 767.98px) {
  .lesson-grid { grid-template-columns: 1fr; }
  .article-cta .btns .btn { width: 100%; justify-content: center; }
  .lesson-nav { flex-direction: column; }
  .lesson-nav a, .lesson-nav .ln-next { max-width: 100%; text-align: left; margin-left: 0; }
}

/* --------------------------------------------------------------------------
   拉丁标点修正
   CJK 字体（Noto Sans/Serif SC）会把 ’ ‘ “ ” 当作全角字符渲染，英文引号
   两侧因此出现异常字距。这里让知识课堂的正文优先命中拉丁字体；中文字符在
   拉丁字体中缺字，会自动回落到后面的 CJK 字体，故中文排版不受影响。
   仅作用于 .learn-page（本栏目），不动全站字体。
   -------------------------------------------------------------------------- */

.learn-page {
  --learn-serif: Georgia, "Liberation Serif", "Times New Roman", "Nimbus Roman",
                 "DejaVu Serif", "Songti SC", "STSong", "SimSun",
                 "Noto Serif SC", "Source Han Serif SC", serif;
  --learn-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
                Arial, "Liberation Sans", "DejaVu Sans",
                "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  font-family: var(--learn-sans);
}
.learn-page h1,
.learn-page h2,
.learn-page h3,
.learn-page .lc-title { font-family: var(--learn-serif); }