/* ============================================================
   AI 研究笔记 · 文章排版样式
   视觉语言与作品集主站一致：深色底 + 橙色点缀 #ef7427
   ============================================================ */

:root {
  --orange: #ef7427;
  --ink: #1a1a1a;
  --paper: #ffffff;
  --paper-soft: #f6f6f4;
  --text: #23262b;
  --text-soft: #5c6169;
  --line: #e7e7e3;
  --maxw: 760px;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: "HarmonyOS Sans SC", -apple-system, BlinkMacSystemFont,
    "PingFang SC", "Microsoft YaHei", "Segoe UI", Roboto, sans-serif;
  color: var(--text);
  background: var(--paper);
  line-height: 1.85;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
}

/* ---------- 顶部导航 ---------- */
.site-header {
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, .86);
  backdrop-filter: saturate(160%) blur(12px);
  position: sticky;
  top: 0;
  z-index: 20;
}

.nav-inner {
  max-width: 1120px;
  margin: 0 auto;
  padding: 16px 28px;
  display: flex;
  align-items: center;
  gap: 28px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 9px;
}

.logo .mark {
  width: 26px;
  height: 26px;
  flex: 0 0 auto;
}

.logo .brand {
  font-weight: 800;
  letter-spacing: .04em;
  font-size: 18px;
  color: var(--ink);
}

.logo .sub {
  font-size: 12.5px;
  color: var(--text-soft);
  padding-left: 9px;
  margin-left: 3px;
  border-left: 1px solid var(--line);
}

.main-nav {
  display: flex;
  gap: 22px;
  margin-left: 8px;
}

.main-nav a {
  color: var(--text-soft);
  text-decoration: none;
  font-size: 14.5px;
  transition: color .2s ease;
}

.main-nav a:hover { color: var(--orange); }

.nav-right {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 18px;
}

.nav-right .search {
  font-size: 14px;
  color: var(--text-soft);
  cursor: pointer;
}

.nav-right .cta {
  border: none;
  background: var(--ink);
  color: #fff;
  padding: 9px 18px;
  border-radius: 999px;
  font-size: 14px;
  cursor: pointer;
  transition: background .2s ease;
}

.nav-right .cta:hover { background: var(--orange); }

/* ---------- 文章容器 ---------- */
.wrap {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px 96px;
}

/* ---------- 标题区 ---------- */
.article-head {
  padding: 64px 0 26px;
}

.article-head h1 {
  font-size: clamp(30px, 5vw, 44px);
  line-height: 1.28;
  font-weight: 800;
  color: var(--ink);
  margin: 0 0 6px;
  letter-spacing: -.01em;
}

.article-head .subtitle {
  font-size: clamp(19px, 3vw, 25px);
  line-height: 1.4;
  font-weight: 700;
  color: var(--orange);
  margin: 0;
}

/* ---------- 导语框 ---------- */
.intro-box {
  background: var(--paper-soft);
  border-left: 3px solid var(--orange);
  border-radius: 0 12px 12px 0;
  padding: 22px 26px;
  margin: 8px 0 40px;
}

.intro-box p {
  margin: 0 0 12px;
  color: var(--text-soft);
  font-size: 16px;
  line-height: 1.8;
}

.intro-box p:last-child { margin-bottom: 0; }

/* ---------- 正文 ---------- */
.content h3 {
  font-size: 22px;
  font-weight: 800;
  color: var(--ink);
  margin: 44px 0 14px;
  padding-top: 6px;
  letter-spacing: -.005em;
}

.content p {
  margin: 0 0 20px;
  text-indent: 2em;
}

.content p.no-indent { text-indent: 0; }

/* 段首加粗小标题（"第一条，最直接的" 等以句号/逗号引导的强调）保持自然 */
.content b { color: var(--ink); font-weight: 700; }

/* ---------- 列表 ---------- */
.article-list {
  margin: 0 0 22px;
  padding-left: 1.4em;
}

.article-list li {
  margin: 0 0 12px;
  line-height: 1.8;
}

.article-list li b { color: var(--ink); }

/* ---------- 配图 ---------- */
.article-img {
  margin: 34px 0;
  text-align: center;
}

.article-img img {
  max-width: 100%;
  height: auto;
  border-radius: 14px;
  display: block;
  margin: 0 auto;
}

/* 配图缺失时的优雅占位：显示 alt 文案，而非裂图图标 */
.article-img img {
  min-height: 60px;
  background: linear-gradient(135deg, #f2f2ef 0%, #eaeae6 100%);
  color: var(--text-soft);
  font-size: 13.5px;
  line-height: 1.6;
  position: relative;
}

/* ---------- 分隔线与来源 ---------- */
.divider {
  border: none;
  border-top: 1px solid var(--line);
  margin: 44px 0 22px;
}

.sources {
  font-size: 13px;
  color: #9a9ea5;
  line-height: 1.7;
  text-indent: 0;
}

/* ---------- 响应式 ---------- */
@media (max-width: 640px) {
  body { font-size: 16px; }
  .main-nav, .nav-right .search { display: none; }
  .nav-inner { padding: 14px 18px; }
  .article-head { padding: 40px 0 20px; }
  .content h3 { font-size: 20px; margin-top: 36px; }
  .intro-box { padding: 18px 20px; }
}