:root {
  --ink: #1a1a1a;
  --ink-soft: #3d3d3d;
  --paper: #fafafa;
  --line: #e8e8e8;
  --gray: #6b6b6b;
  --gray-light: #9a9a9a;
  --accent: #c0392b;
  --accent-soft: #f4e4e1;
  --surface: #ffffff;
  --radius: 6px;
  --radius-sm: 4px;
  --shell: 1120px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

/* ============================================================
   base
   ============================================================ */
*,
*::before,
*::after {
  box-sizing: border-box;
}

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

.site-body {
  margin: 0;
  padding: 0;
  background-color: var(--paper);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  margin: 0;
  line-height: 1.35;
  font-weight: 700;
  color: var(--ink);
}

p {
  margin: 0;
}

ul,
ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

dl,
dd,
dt,
figure,
figcaption {
  margin: 0;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover,
a:focus {
  text-decoration: underline;
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

button {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

table {
  border-collapse: collapse;
  width: 100%;
}

th,
td {
  text-align: left;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 60;
  padding: 10px 16px;
  background-color: var(--ink);
  color: #ffffff;
  border-radius: 0 0 var(--radius-sm) 0;
  transform: translateY(-120%);
  transition: transform 0.18s ease;
}

.skip-link:focus {
  transform: translateY(0);
  text-decoration: none;
}

/* ============================================================
   layout — 全站骨架
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background-color: rgba(250, 250, 250, 0.96);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px 24px;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 14px 24px;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 2px;
  color: var(--ink);
  text-decoration: none;
}

.brand:hover,
.brand:focus {
  text-decoration: none;
}

.brand-name {
  font-size: 20px;
  font-weight: 700;
  line-height: 1.2;
}

.brand-slogan {
  font-size: 12px;
  color: var(--gray);
  line-height: 1.4;
}

.site-nav {
  margin-left: auto;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav-list li {
  display: block;
}

.nav-list a {
  display: block;
  padding: 10px 14px;
  min-height: 44px;
  font-size: 15px;
  color: var(--ink-soft);
  border-bottom: 2px solid transparent;
  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
  text-decoration: none;
  transition: color 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
}

.nav-list a:hover,
.nav-list a:focus {
  color: var(--accent);
  background-color: var(--accent-soft);
  text-decoration: none;
}

.nav-list a.is-current {
  color: var(--accent);
  font-weight: 600;
  border-bottom-color: var(--accent);
}

.nav-toggle {
  display: none;
  margin-left: auto;
  width: 44px;
  height: 44px;
  padding: 10px;
  background-color: transparent;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  cursor: pointer;
}

.nav-toggle-bar {
  display: block;
  width: 100%;
  height: 2px;
  margin: 4px 0;
  background-color: var(--ink);
  border-radius: 2px;
}

.site-main {
  display: block;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 32px 24px 56px;
}

.inner-main {
  padding-top: 24px;
}

.breadcrumb {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
  font-size: 14px;
  color: var(--gray);
}

.breadcrumb a {
  color: var(--gray);
  text-decoration: none;
}

.breadcrumb a:hover,
.breadcrumb a:focus {
  color: var(--accent);
  text-decoration: underline;
}

.breadcrumb-sep {
  color: var(--gray-light);
}

.breadcrumb-current {
  color: var(--ink);
}

.page-header {
  margin-bottom: 32px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--line);
}

.page-title {
  font-size: 32px;
  font-weight: 700;
  color: var(--ink);
}

.page-description,
.page-lead {
  margin-top: 12px;
  max-width: 68ch;
  font-size: 15px;
  color: var(--gray);
}

.page-lead {
  margin-top: 8px;
}

.page-layout {
  display: grid;
  gap: 40px;
}

.layout-shell {
  grid-template-columns: minmax(0, 1fr) 300px;
}

.layout-main {
  min-width: 0;
}

.layout-aside {
  min-width: 0;
}

.site-footer {
  background-color: var(--surface);
  border-top: 1px solid var(--line);
}

.footer-inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 36px 24px 28px;
}

.footer-back {
  margin-bottom: 20px;
  font-size: 14px;
}

.footer-back a {
  color: var(--gray);
  text-decoration: none;
}

.footer-back a:hover,
.footer-back a:focus {
  color: var(--accent);
  text-decoration: underline;
}

.footer-brand {
  padding-bottom: 20px;
  border-bottom: 1px solid var(--line);
}

.footer-brand-name {
  font-size: 18px;
  font-weight: 700;
}

.footer-brand-desc {
  margin-top: 6px;
  max-width: 68ch;
  font-size: 14px;
  color: var(--gray);
}

.footer-groups {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 28px;
  margin-top: 24px;
}

.footer-group-title {
  margin-bottom: 10px;
  font-size: 15px;
  font-weight: 700;
}

.footer-links li {
  margin-bottom: 8px;
}

.footer-links a {
  font-size: 14px;
  color: var(--gray);
  text-decoration: none;
}

.footer-links a:hover,
.footer-links a:focus {
  color: var(--accent);
  text-decoration: underline;
}

.footer-copy {
  margin-top: 28px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  font-size: 13px;
  color: var(--gray-light);
}

/* ============================================================
   components — 通用组件
   ============================================================ */
.section {
  margin-bottom: 48px;
}

.section:last-child {
  margin-bottom: 0;
}

.section-head {
  margin-bottom: 20px;
}

.section-title {
  font-size: 24px;
  font-weight: 700;
}

.section-desc,
.section-intro,
.section-lead {
  margin-top: 8px;
  max-width: 68ch;
  font-size: 15px;
  color: var(--gray);
}

.section-more {
  margin-top: 16px;
  font-size: 14px;
}

.section-more a {
  font-weight: 600;
}

.section-note {
  margin-top: 18px;
  padding-top: 14px;
  border-top: 1px dashed var(--line);
  font-size: 14px;
  color: var(--gray);
}

.section-note a {
  margin-right: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 20px;
  font-size: 15px;
  font-weight: 600;
  border-radius: var(--radius);
  border: 1px solid transparent;
  text-decoration: none;
  transition: background-color 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}

.btn:hover,
.btn:focus {
  text-decoration: none;
}

.btn-primary {
  background-color: var(--accent);
  color: #ffffff;
}

.btn-primary:hover,
.btn-primary:focus {
  background-color: #a5311f;
  color: #ffffff;
}

.btn-ghost {
  background-color: transparent;
  color: var(--ink);
  border-color: var(--line);
}

.btn-ghost:hover,
.btn-ghost:focus {
  color: var(--accent);
  border-color: var(--accent);
  background-color: var(--accent-soft);
}

.tag {
  display: inline-block;
  margin: 0 6px 4px 0;
  padding: 2px 8px;
  font-size: 12px;
  line-height: 1.6;
  color: var(--gray);
  background-color: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
}

.tag-direction {
  color: var(--accent);
  background-color: var(--accent-soft);
  border-color: #eccfc9;
}

.tag-status {
  color: var(--ink-soft);
}

/* 字段口径表 */
.field-table {
  font-size: 14px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.field-table-caption {
  padding: 12px 16px;
  text-align: left;
  font-size: 14px;
  font-weight: 600;
  color: var(--gray);
  background-color: var(--paper);
  border-bottom: 1px solid var(--line);
}

.field-table thead th {
  padding: 12px 16px;
  font-size: 13px;
  font-weight: 700;
  color: var(--ink);
  background-color: var(--paper);
  border-bottom: 1px solid var(--line);
}

.field-table tbody th,
.field-table tbody td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
  color: var(--ink-soft);
}

.field-table tbody tr:last-child th,
.field-table tbody tr:last-child td {
  border-bottom: 0;
}

.field-table tbody th {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 600;
  color: var(--ink);
  white-space: nowrap;
}

/* 编号步骤 */
.step-list {
  display: grid;
  gap: 16px;
}

.step-item {
  padding: 18px 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
}

.step-no,
.step-index {
  display: inline-block;
  margin-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--accent);
}

.step-name,
.step-title {
  font-size: 18px;
  font-weight: 700;
}

.step-text,
.step-desc {
  margin-top: 8px;
  font-size: 15px;
  color: var(--gray);
}

/* 侧栏通用 */
.aside-title,
.sidebar-title {
  font-size: 18px;
  font-weight: 700;
}

.aside-text {
  margin-top: 8px;
  font-size: 14px;
  color: var(--gray);
}

.aside-block {
  margin-bottom: 24px;
  padding: 18px 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.aside-block:last-child {
  margin-bottom: 0;
}

.aside-block-title {
  margin-bottom: 10px;
  font-size: 16px;
  font-weight: 700;
}

.aside-link-list li,
.aside-links li {
  margin-bottom: 8px;
}

.aside-link-list a,
.aside-links a {
  font-size: 14px;
  color: var(--ink-soft);
}

.aside-link-list a:hover,
.aside-link-list a:focus,
.aside-links a:hover,
.aside-links a:focus {
  color: var(--accent);
}

/* ============================================================
   pages — 首页
   ============================================================ */
.fact-bar {
  background-color: var(--ink);
  color: #e8e8e8;
}

.fact-bar p {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 8px 24px;
  font-size: 13px;
}

.home-main {
  padding-top: 36px;
}

/* 首屏 */
.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 460px);
  gap: 40px;
  align-items: start;
  margin-bottom: 56px;
}

.hero-copy {
  min-width: 0;
}

.hero-eyebrow {
  margin-bottom: 12px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--accent);
}

.hero-title {
  font-size: 32px;
  font-weight: 700;
  color: var(--ink);
}

.hero-lead {
  margin-top: 16px;
  max-width: 62ch;
  font-size: 16px;
  color: var(--gray);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 24px;
}

.hero-facts {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  margin-top: 32px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.fact-item dt {
  font-size: 13px;
  color: var(--gray);
}

.fact-item dd {
  margin-top: 4px;
  font-size: 15px;
  font-weight: 600;
  color: var(--ink);
}

.hero-media {
  min-width: 0;
}

.hero-media img {
  width: 100%;
  height: 320px;
  object-fit: cover;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.hero-media figcaption {
  margin-top: 10px;
  font-size: 13px;
  color: var(--gray);
}

/* 题材方向总览 */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 20px;
}

.topic-card {
  padding: 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  transition: border-color 0.15s ease, transform 0.15s ease;
}

.topic-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.topic-name {
  font-size: 18px;
  font-weight: 700;
}

.topic-scope {
  margin-top: 10px;
  font-size: 14px;
  color: var(--gray);
}

.topic-sample {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px dashed var(--line);
  font-size: 14px;
}

/* 并列区 */
.section-split {
  display: grid;
  grid-template-columns: minmax(0, 1.55fr) minmax(0, 1fr);
  gap: 40px;
  align-items: start;
}

.split-column {
  min-width: 0;
}

/* 封面条目速览 */
.cover-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
}

.cover-card {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  transition: transform 0.15s ease, border-color 0.15s ease;
}

.cover-card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.cover-figure {
  background-color: var(--line);
}

.cover-figure img {
  width: 100%;
  height: 150px;
  object-fit: cover;
}

.cover-body {
  padding: 12px 14px 14px;
}

.cover-name {
  font-size: 15px;
  font-weight: 700;
}

.cover-tags {
  margin-top: 8px;
  font-size: 12px;
  color: var(--gray);
}

.cover-tags .tag {
  margin-right: 4px;
}

/* 更新批次清单 */
.batch-list {
  display: grid;
  gap: 18px;
}

.batch-group {
  padding: 16px 18px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.batch-heading {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  font-size: 16px;
  font-weight: 700;
}

.batch-code {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--accent);
}

.batch-name {
  font-size: 14px;
  color: var(--ink-soft);
}

.batch-items {
  margin-top: 12px;
  border-top: 1px dashed var(--line);
}

.batch-item {
  padding: 10px 0;
  border-bottom: 1px dashed var(--line);
  font-size: 14px;
  color: var(--ink-soft);
}

.batch-item:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.batch-field {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--gray);
}

.batch-topic {
  color: var(--gray);
}

/* 人气位次参考 */
.rank-list {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.rank-item {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 12px 16px;
  border-bottom: 1px solid var(--line);
}

.rank-item:last-child {
  border-bottom: 0;
}

.rank-no {
  flex: 0 0 28px;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--accent);
}

.rank-name {
  font-size: 15px;
  font-weight: 600;
}

.rank-topic {
  margin-left: auto;
  font-size: 13px;
  color: var(--gray);
}

.rank-basis {
  margin-top: 12px;
  font-size: 14px;
  color: var(--gray);
}

/* 字段口径摘要 */
.split-fields {
  min-width: 0;
}

/* 站内栏目索引 */
.index-grid {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 18px;
}

.index-column {
  padding: 16px 18px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.index-name {
  font-size: 16px;
  font-weight: 700;
}

.index-desc {
  margin-top: 8px;
  font-size: 14px;
  color: var(--gray);
}

/* ============================================================
   pages — 题材分类
   ============================================================ */
.topic-layout {
  grid-template-columns: minmax(0, 1fr) 300px;
}

.topic-main {
  min-width: 0;
}

.topic-overview,
.topic-detail,
.topic-titles {
  margin-bottom: 40px;
}

.topic-overview:last-child,
.topic-detail:last-child,
.topic-titles:last-child {
  margin-bottom: 0;
}

.topic-row-list {
  margin-top: 18px;
  border-top: 1px solid var(--line);
}

.topic-row {
  display: grid;
  grid-template-columns: 140px minmax(0, 1fr) 120px;
  gap: 16px;
  align-items: baseline;
  padding: 14px 0;
  border-bottom: 1px solid var(--line);
}

.topic-row-name {
  font-size: 16px;
  font-weight: 700;
}

.topic-row-scope {
  font-size: 14px;
  color: var(--gray);
}

.topic-row-count {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--gray);
  text-align: right;
}

.topic-detail-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
  margin-top: 18px;
}

.topic-detail-block {
  padding: 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.topic-detail-name {
  font-size: 18px;
  font-weight: 700;
}

.topic-detail-scope {
  margin-top: 10px;
  font-size: 14px;
  color: var(--ink-soft);
}

.topic-detail-feature {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px dashed var(--line);
  font-size: 14px;
  color: var(--gray);
}

.title-card-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
  margin-top: 18px;
}

.title-card {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  transition: transform 0.15s ease, border-color 0.15s ease;
}

.title-card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.title-card-figure {
  background-color: var(--line);
}

.title-card-figure img {
  width: 100%;
  height: 140px;
  object-fit: cover;
}

.title-card-name {
  padding: 12px 14px 0;
  font-size: 15px;
  font-weight: 700;
}

.title-card-tags {
  padding: 8px 14px 14px;
  font-size: 12px;
  color: var(--gray);
}

.topic-aside {
  min-width: 0;
}

.direction-index {
  margin: 18px 0 24px;
  padding: 18px 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.direction-index-list li {
  margin-bottom: 8px;
}

.direction-index-list a {
  font-size: 14px;
  color: var(--ink-soft);
}

.direction-index-list a:hover,
.direction-index-list a:focus {
  color: var(--accent);
}

/* ============================================================
   pages — 更新记录
   ============================================================ */
.updates-batches,
.updates-fields,
.updates-tips {
  margin-bottom: 40px;
}

.updates-batches:last-child,
.updates-fields:last-child,
.updates-tips:last-child {
  margin-bottom: 0;
}

.batch-group {
  margin-top: 20px;
}

.batch-head {
  padding-bottom: 10px;
  border-bottom: 2px solid var(--ink);
}

.batch-title {
  font-size: 18px;
  font-weight: 700;
}

.batch-meta {
  margin-top: 4px;
  font-size: 13px;
  color: var(--gray);
}

.batch-list {
  margin-top: 4px;
}

.batch-item {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 160px 120px;
  gap: 16px;
  align-items: baseline;
  padding: 12px 0;
  border-bottom: 1px solid var(--line);
}

.batch-item-name {
  font-size: 15px;
  font-weight: 600;
}

.batch-item-field {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--gray);
}

.batch-item-topic {
  font-size: 13px;
  color: var(--gray);
  text-align: right;
}

.updates-figure {
  margin-top: 24px;
}

.updates-figure img {
  width: 100%;
  height: 220px;
  object-fit: cover;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.updates-figure figcaption {
  margin-top: 10px;
  font-size: 13px;
  color: var(--gray);
}

.updates-aside {
  min-width: 0;
}

/* ============================================================
   pages — 人气位次
   ============================================================ */
.ranking-layout {
  grid-template-columns: minmax(0, 1fr) 300px;
  align-items: start;
}

.ranking-list-section {
  min-width: 0;
}

.ranking-list {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.ranking-item {
  display: grid;
  grid-template-columns: 40px 84px minmax(0, 1fr);
  gap: 16px;
  align-items: center;
  padding: 14px 18px;
  border-bottom: 1px solid var(--line);
}

.ranking-item:last-child {
  border-bottom: 0;
}

.ranking-index {
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 700;
  color: var(--accent);
}

.ranking-cover {
  background-color: var(--line);
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.ranking-cover img {
  width: 84px;
  height: 60px;
  object-fit: cover;
}

.ranking-body {
  min-width: 0;
}

.ranking-name {
  font-size: 16px;
  font-weight: 700;
}

.ranking-topic {
  margin-top: 4px;
  font-size: 13px;
  color: var(--gray);
}

.ranking-reason {
  margin-top: 6px;
  font-size: 14px;
  color: var(--ink-soft);
}

.ranking-sidebar {
  min-width: 0;
}

.basis-block {
  margin-top: 16px;
  padding: 18px 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.basis-title {
  margin-bottom: 8px;
  font-size: 16px;
  font-weight: 700;
}

.basis-block p {
  font-size: 14px;
  color: var(--gray);
}

.sidebar-note {
  margin-top: 16px;
  font-size: 14px;
  color: var(--gray);
}

.sidebar-note a {
  margin-right: 12px;
}

.ranking-howto-section .step-list {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.ranking-steps .step-item {
  display: flex;
  flex-direction: column;
}

.related-links {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 16px;
}

.related-item a {
  display: block;
  padding: 14px 16px;
  min-height: 44px;
  font-size: 15px;
  color: var(--ink-soft);
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  text-decoration: none;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.related-item a:hover,
.related-item a:focus {
  color: var(--accent);
  border-color: var(--accent);
  text-decoration: none;
}

/* ============================================================
   pages — 查阅指引
   ============================================================ */
.section-fields,
.section-path,
.section-boundary,
.section-faq {
  margin-bottom: 44px;
}

.section-faq:last-child {
  margin-bottom: 0;
}

.field-table-wrap {
  overflow-x: auto;
}

.field-figure {
  margin-top: 24px;
}

.field-figure img {
  width: 100%;
  height: 240px;
  object-fit: cover;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.field-figure figcaption {
  margin-top: 10px;
  font-size: 13px;
  color: var(--gray);
}

.path-steps {
  display: grid;
  gap: 18px;
}

.path-step {
  padding: 20px 22px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
}

.path-step .step-index {
  display: inline-block;
  margin-bottom: 8px;
}

.step-detail {
  display: grid;
  grid-template-columns: 84px minmax(0, 1fr);
  gap: 8px 16px;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px dashed var(--line);
}

.step-detail dt {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--gray);
}

.step-detail dd {
  font-size: 15px;
  color: var(--ink-soft);
}

.path-figure {
  margin-top: 24px;
}

.path-figure img {
  width: 100%;
  height: 220px;
  object-fit: cover;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.path-figure figcaption {
  margin-top: 10px;
  font-size: 13px;
  color: var(--gray);
}

.boundary-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
}

.boundary-item {
  padding: 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.boundary-title {
  font-size: 17px;
  font-weight: 700;
}

.boundary-item p {
  margin-top: 10px;
  font-size: 15px;
  color: var(--gray);
}

.boundary-list {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px dashed var(--line);
}

.boundary-list li {
  position: relative;
  padding-left: 16px;
  margin-bottom: 6px;
  font-size: 14px;
  color: var(--ink-soft);
}

.boundary-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 10px;
  width: 5px;
  height: 5px;
  background-color: var(--accent);
  border-radius: 50%;
}

.boundary-feedback {
  margin-top: 20px;
  padding: 20px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.boundary-feedback p {
  margin-top: 10px;
  font-size: 15px;
  color: var(--gray);
}

.boundary-links a {
  display: inline-block;
  margin: 0 14px 6px 0;
  font-size: 14px;
  font-weight: 600;
}

.faq-list {
  border-top: 1px solid var(--line);
}

.faq-item {
  border-bottom: 1px solid var(--line);
}

.faq-question {
  padding: 16px 0;
  font-size: 16px;
  font-weight: 600;
  color: var(--ink);
  cursor: pointer;
  list-style: none;
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::before {
  content: "+";
  display: inline-block;
  width: 18px;
  margin-right: 8px;
  font-family: var(--font-mono);
  color: var(--accent);
}

.faq-item[open] .faq-question::before {
  content: "−";
}

.faq-answer {
  padding: 0 0 16px 26px;
}

.faq-answer p {
  font-size: 15px;
  color: var(--gray);
}

/* ============================================================
   pages — 404
   ============================================================ */
.error-main {
  display: flex;
  justify-content: center;
  padding-top: 64px;
  padding-bottom: 80px;
}

.error-panel {
  max-width: 640px;
  padding: 40px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  text-align: left;
}

.error-code {
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 700;
  color: var(--accent);
}

.error-panel h1 {
  margin-top: 10px;
  font-size: 28px;
  font-weight: 700;
}

.error-desc {
  margin-top: 14px;
  font-size: 15px;
  color: var(--gray);
}

.error-actions {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 24px;
}

.error-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 16px;
  font-size: 15px;
  font-weight: 600;
  color: var(--ink-soft);
  background-color: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  text-decoration: none;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.error-btn:hover,
.error-btn:focus {
  color: var(--accent);
  border-color: var(--accent);
  text-decoration: none;
}

/* ============================================================
   responsive
   ============================================================ */
@media (max-width: 1024px) {
  .hero {
    grid-template-columns: minmax(0, 1fr) minmax(0, 380px);
    gap: 32px;
  }

  .topic-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .index-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .title-card-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .ranking-howto-section .step-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .related-links {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 900px) {
  .layout-shell,
  .topic-layout,
  .ranking-layout {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
  }

  .section-split {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
  }

  .hero {
    grid-template-columns: minmax(0, 1fr);
  }

  .hero-media img {
    height: 260px;
  }
}

@media (max-width: 768px) {
  .header-inner {
    padding: 12px 16px;
    gap: 10px;
  }

  .nav-toggle {
    display: block;
  }

  .site-nav {
    flex-basis: 100%;
    margin-left: 0;
  }

  .nav-list {
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    width: 100%;
    padding: 6px 0;
    border-top: 1px solid var(--line);
  }

  .nav-list.is-open {
    display: flex;
  }

  .nav-list a {
    padding: 12px 4px;
    border-bottom: 0;
    border-left: 2px solid transparent;
    border-radius: 0;
  }

  .nav-list a.is-current {
    border-bottom-color: transparent;
    border-left-color: var(--accent);
  }

  .site-main {
    padding: 24px 16px 44px;
  }

  .page-title {
    font-size: 26px;
  }

  .hero-title {
    font-size: 26px;
  }

  .section-title {
    font-size: 21px;
  }

  .hero-facts {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .cover-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .topic-detail-grid,
  .boundary-columns {
    grid-template-columns: minmax(0, 1fr);
  }

  .title-card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .ranking-howto-section .step-list,
  .related-links {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .topic-row {
    grid-template-columns: minmax(0, 1fr);
    gap: 6px;
  }

  .topic-row-count {
    text-align: left;
  }

  .batch-item {
    grid-template-columns: minmax(0, 1fr);
    gap: 4px;
  }

  .batch-item-topic {
    text-align: left;
  }

  .ranking-item {
    grid-template-columns: 32px 72px minmax(0, 1fr);
    gap: 12px;
    padding: 14px;
  }

  .ranking-cover img {
    width: 72px;
    height: 52px;
  }

  .footer-groups {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 22px;
  }

  .step-detail {
    grid-template-columns: minmax(0, 1fr);
    gap: 4px;
  }

  .step-detail dd {
    margin-bottom: 8px;
  }

  .error-panel {
    padding: 28px 22px;
  }
}

@media (max-width: 480px) {
  .brand-slogan {
    display: none;
  }

  .fact-bar p {
    padding: 8px 16px;
    font-size: 12px;
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .hero-facts {
    grid-template-columns: minmax(0, 1fr);
    gap: 12px;
  }

  .topic-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .cover-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 12px;
  }

  .title-card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 12px;
  }

  .index-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .ranking-howto-section .step-list,
  .related-links {
    grid-template-columns: minmax(0, 1fr);
  }

  .ranking-item {
    grid-template-columns: 28px minmax(0, 1fr);
    row-gap: 8px;
  }

  .ranking-cover {
    grid-column: 2;
  }

  .ranking-body {
    grid-column: 2;
  }

  .footer-groups {
    grid-template-columns: minmax(0, 1fr);
  }

  .error-actions {
    grid-template-columns: minmax(0, 1fr);
  }

  .field-table thead th,
  .field-table tbody th,
  .field-table tbody td {
    padding: 10px 12px;
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
  }
}