/* ==========================================================================
   九九免费视频 · 全站样式表
   分组：base / layout / components / pages / responsive
   ========================================================================== */

/* --------------------------------------------------------------------------
   base · 变量与基础排版
   -------------------------------------------------------------------------- */
:root {
  --c-primary: #1f4d3f;
  --c-primary-dark: #163a30;
  --c-accent: #d97a34;
  --c-bg: #f5f6f4;
  --c-card: #ffffff;
  --c-text: #22302b;
  --c-muted: #5c6b64;
  --c-info: #2f6db5;
  --c-line: #dfe3df;
  --c-line-soft: #eaeeea;
  --radius: 8px;
  --radius-sm: 5px;
  --shadow-sm: 0 1px 2px rgba(31, 77, 63, 0.06);
  --shadow-md: 0 4px 14px rgba(31, 77, 63, 0.09);
  --shell: 1120px;
  --shell-pad: 20px;
  --font-sans: system-ui, -apple-system, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
}

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

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

body {
  margin: 0;
  background: var(--c-bg);
  color: var(--c-text);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

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

p {
  margin: 0;
}

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

a {
  color: var(--c-primary);
  text-decoration: none;
  transition: color 0.18s ease, border-color 0.18s ease;
}

a:hover,
a:focus-visible {
  color: var(--c-accent);
}

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

button {
  font: inherit;
  color: inherit;
  cursor: pointer;
}

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

:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}

/* --------------------------------------------------------------------------
   layout · 全站骨架：body / header / nav / main / breadcrumb / page-header / footer
   -------------------------------------------------------------------------- */
.site-body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--c-bg);
  color: var(--c-text);
  font-family: var(--font-sans);
}

/* 顶部信息条 */
.topbar {
  background: var(--c-primary);
  color: #e7efe9;
}

.topbar-text {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 8px var(--shell-pad);
  font-size: 13px;
  line-height: 1.6;
  text-align: center;
}

/* 页头 */
.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: #ffffff;
  border-bottom: 1px solid var(--c-line);
}

.header-inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 var(--shell-pad);
  height: 64px;
  display: flex;
  align-items: center;
  gap: 18px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  flex: 0 0 auto;
  color: var(--c-primary);
  font-weight: 700;
}

.brand:hover,
.brand:focus-visible {
  color: var(--c-primary-dark);
}

.brand-mark {
  width: 26px;
  height: 26px;
  border-radius: var(--radius-sm);
  background: var(--c-primary);
  position: relative;
  flex: 0 0 auto;
}

.brand-mark::after {
  content: "";
  position: absolute;
  inset: 8px 7px auto 7px;
  height: 3px;
  background: var(--c-accent);
  border-radius: 2px;
  box-shadow: 0 6px 0 var(--c-accent);
}

.brand-name {
  font-size: 18px;
  letter-spacing: 0;
  white-space: nowrap;
}

/* 主导航 */
.site-nav {
  margin-left: auto;
}

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

.nav-item {
  display: block;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 0 14px;
  border-radius: var(--radius-sm);
  color: var(--c-text);
  font-size: 15px;
  border: 1px solid transparent;
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--c-primary);
  border-color: var(--c-line);
  background: #f7f9f7;
}

.nav-link.is-current {
  color: var(--c-primary);
  font-weight: 700;
  background: #eef3ef;
  border-color: #d6e2d9;
}

/* 汉堡按钮 */
.nav-toggle {
  display: none;
  margin-left: auto;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 1px solid var(--c-line);
  border-radius: var(--radius-sm);
  background: #ffffff;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
}

.nav-toggle-bar {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--c-primary);
  border-radius: 2px;
}

/* 主内容 */
.site-main {
  flex: 1 0 auto;
  width: 100%;
}

.home-main {
  display: block;
}

.inner-main {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 22px var(--shell-pad) 56px;
}

/* 面包屑 */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--c-muted);
  margin-bottom: 14px;
}

.breadcrumb a {
  color: var(--c-muted);
}

.breadcrumb a:hover,
.breadcrumb a:focus-visible {
  color: var(--c-accent);
}

.breadcrumb-sep {
  color: #a9b4ae;
}

.breadcrumb-current {
  color: var(--c-primary);
  font-weight: 600;
}

/* 内页标题区 */
.page-header {
  padding: 0 0 20px;
  border-bottom: 1px solid var(--c-line);
  margin-bottom: 28px;
}

.page-title {
  font-size: 28px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 10px;
}

.page-description {
  max-width: 720px;
  color: var(--c-muted);
  font-size: 15px;
  line-height: 1.8;
}

/* 页脚 */
.site-footer {
  background: #ffffff;
  border-top: 1px solid var(--c-line);
  margin-top: auto;
}

.footer-inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 40px var(--shell-pad) 26px;
  display: grid;
  grid-template-columns: minmax(220px, 1.4fr) repeat(3, minmax(150px, 1fr));
  gap: 28px;
}

.footer-brand {
  min-width: 0;
}

.footer-name {
  color: var(--c-primary);
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 10px;
}

.footer-desc {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  max-width: 320px;
}

.footer-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 12px;
}

.footer-list {
  display: flex;
  flex-direction: column;
  gap: 9px;
}

.footer-list a {
  color: var(--c-muted);
  font-size: 14px;
  display: inline-flex;
  align-items: center;
  min-height: 24px;
}

.footer-list a:hover,
.footer-list a:focus-visible {
  color: var(--c-accent);
}

.footer-bottom {
  border-top: 1px solid var(--c-line-soft);
  background: #fbfcfb;
}

.copyright {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 16px var(--shell-pad);
  color: var(--c-muted);
  font-size: 13px;
  line-height: 1.7;
}

/* 移动端底部快捷条 */
.mobile-bar {
  display: none;
}

/* --------------------------------------------------------------------------
   components · 通用组件
   -------------------------------------------------------------------------- */

/* 按钮 */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 20px;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 600;
  border: 1px solid transparent;
  transition: background 0.18s ease, color 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
}

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

.btn-primary:hover,
.btn-primary:focus-visible {
  background: var(--c-primary-dark);
  border-color: var(--c-primary-dark);
  color: #ffffff;
  transform: translateY(-1px);
}

.btn-ghost {
  background: #ffffff;
  color: var(--c-primary);
  border-color: #cbd8d0;
}

.btn-ghost:hover,
.btn-ghost:focus-visible {
  border-color: var(--c-accent);
  color: var(--c-accent);
  transform: translateY(-1px);
}

/* 区块与区块标题 */
.section {
  padding: 40px 0;
  border-top: 1px solid var(--c-line-soft);
}

.home-main .section {
  max-width: var(--shell);
  margin: 0 auto;
  padding-left: var(--shell-pad);
  padding-right: var(--shell-pad);
}

.section-head {
  margin-bottom: 22px;
}

.section-title {
  font-size: 20px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 8px;
}

.section-desc {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  max-width: 760px;
}

.inner-main .section {
  padding: 30px 0 0;
  border-top: 0;
}

.inner-main .section + .section {
  margin-top: 34px;
  padding-top: 30px;
  border-top: 1px solid var(--c-line-soft);
}

.subsection-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 12px;
}

.col-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 14px;
}

/* 表格 */
.table-wrap,
.table-scroll {
  width: 100%;
  overflow-x: auto;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
}

.data-table {
  width: 100%;
  min-width: 620px;
  font-size: 14px;
}

.table-caption {
  caption-side: top;
  text-align: left;
  padding: 12px 16px 0;
  color: var(--c-muted);
  font-size: 13px;
}

.data-table thead th {
  background: #f2f5f2;
  color: var(--c-primary);
  font-weight: 700;
  text-align: left;
  padding: 12px 16px;
  border-bottom: 1px solid var(--c-line);
  white-space: nowrap;
}

.data-table tbody th,
.data-table tbody td {
  padding: 13px 16px;
  border-bottom: 1px solid var(--c-line-soft);
  vertical-align: top;
  line-height: 1.7;
}

.data-table tbody th {
  text-align: left;
  color: var(--c-primary);
  font-weight: 700;
  white-space: nowrap;
}

.data-table tbody td {
  color: var(--c-muted);
}

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

.data-table tbody tr:hover th,
.data-table tbody tr:hover td {
  background: #f8faf8;
}

/* 图片容器 */
.figure,
.guide-figure,
.media-figure,
.hero-media,
.topic-media,
.topic-feature-media {
  margin: 0;
  overflow: hidden;
  border-radius: var(--radius);
  background: #e8ece8;
}

.figure img,
.guide-figure img,
.media-figure img,
.hero-media img,
.topic-media img,
.topic-feature-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.figure-caption,
.guide-figure figcaption,
.media-figure figcaption,
.hero-media figcaption {
  padding: 10px 14px;
  font-size: 13px;
  color: var(--c-muted);
  background: #ffffff;
  border-top: 1px solid var(--c-line-soft);
  line-height: 1.7;
}

/* 折叠问答 */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.faq-item {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  overflow: hidden;
}

.faq-question {
  position: relative;
  padding: 14px 44px 14px 16px;
  font-size: 15px;
  font-weight: 600;
  color: var(--c-primary);
  cursor: pointer;
  list-style: none;
  line-height: 1.7;
}

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

.faq-question::after {
  content: "+";
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 18px;
  color: var(--c-accent);
  font-weight: 700;
}

.faq-item[open] .faq-question::after {
  content: "–";
}

.faq-question:hover {
  background: #f8faf8;
}

.faq-answer {
  padding: 0 16px 16px;
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
  border-top: 1px solid var(--c-line-soft);
  padding-top: 14px;
}

/* 列表型关系条目 */
.relation-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.relation-item {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 16px 18px;
}

.relation-heading {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 6px;
}

.relation-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
}

/* 侧栏通用 */
.aside-block {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 18px;
}

.aside-block + .aside-block {
  margin-top: 18px;
}

.aside-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 10px;
}

.aside-desc {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  margin-bottom: 12px;
}

.aside-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
}

.aside-links {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.aside-link-item {
  display: block;
  padding: 10px 12px;
  border: 1px solid var(--c-line);
  border-radius: var(--radius-sm);
  background: #fafbfa;
}

.aside-link-item:hover,
.aside-link-item:focus-visible {
  border-color: var(--c-accent);
}

.aside-link-note {
  display: block;
  margin-top: 4px;
  color: var(--c-muted);
  font-size: 13px;
  line-height: 1.7;
}

.check-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.check-item {
  position: relative;
  padding-left: 20px;
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
}

.check-item::before {
  content: "";
  position: absolute;
  left: 2px;
  top: 9px;
  width: 7px;
  height: 7px;
  border-radius: 2px;
  background: var(--c-accent);
}

/* 箭头链接 */
.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  font-weight: 600;
  color: var(--c-primary);
  border-bottom: 1px solid #c6d5cc;
  padding-bottom: 1px;
}

.link-arrow::after {
  content: "›";
  font-size: 16px;
  color: var(--c-accent);
}

.link-arrow:hover,
.link-arrow:focus-visible {
  color: var(--c-accent);
  border-color: var(--c-accent);
}

.label-inline {
  display: inline-block;
  margin-right: 6px;
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  background: #eef3ef;
  color: var(--c-primary);
  font-size: 13px;
  font-weight: 600;
}

/* --------------------------------------------------------------------------
   pages · 首页
   -------------------------------------------------------------------------- */
.hero {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 38px var(--shell-pad) 34px;
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(280px, 1fr);
  gap: 32px;
  align-items: start;
}

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

.hero-eyebrow {
  display: inline-block;
  padding: 4px 12px;
  border-radius: var(--radius-sm);
  background: #eef3ef;
  color: var(--c-primary);
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 14px;
}

.hero-title {
  font-size: 32px;
  font-weight: 700;
  color: var(--c-primary);
  line-height: 1.32;
  margin-bottom: 14px;
}

.hero-lead {
  max-width: 620px;
  color: var(--c-muted);
  font-size: 16px;
  line-height: 1.85;
  margin-bottom: 20px;
}

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

.hero-media {
  border: 1px solid var(--c-line);
}

.hero-media img {
  aspect-ratio: 16 / 9;
}

.hero-side {
  display: grid;
  gap: 18px;
  min-width: 0;
}

.hero-panel {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 18px;
}

.panel-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 8px;
}

.panel-note {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  margin-bottom: 14px;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tag a {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  padding: 0 12px;
  border: 1px solid var(--c-line);
  border-radius: var(--radius-sm);
  background: #fafbfa;
  color: var(--c-text);
  font-size: 14px;
}

.tag a:hover,
.tag a:focus-visible {
  border-color: var(--c-accent);
  color: var(--c-accent);
  transform: translateY(-1px);
}

/* 频道分类总览 */
.section-channels .table-wrap {
  margin-top: 4px;
}

/* 本期专题策展 */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
}

.topic-card {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.topic-card:hover,
.topic-card:focus-within {
  border-color: #c3d3c8;
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.topic-media {
  border-radius: 0;
}

.topic-media img {
  aspect-ratio: 16 / 10;
}

.topic-name {
  font-size: 17px;
  font-weight: 700;
  color: var(--c-primary);
  margin: 14px 16px 8px;
}

.topic-name a {
  color: inherit;
}

.topic-name a:hover,
.topic-name a:focus-visible {
  color: var(--c-accent);
}

.topic-scope {
  margin: 0 16px 8px;
  color: var(--c-text);
  font-size: 14px;
  line-height: 1.8;
}

.topic-note {
  margin: 0 16px 16px;
  color: var(--c-muted);
  font-size: 13px;
  line-height: 1.8;
  padding-left: 10px;
  border-left: 2px solid var(--c-line);
}

/* 观看指引摘要 */
.guide-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 22px;
}

.guide-col {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 18px;
  min-width: 0;
}

.step-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  counter-reset: step;
}

.step-item {
  position: relative;
  padding-left: 30px;
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  counter-increment: step;
}

.step-item::before {
  content: counter(step);
  position: absolute;
  left: 0;
  top: 3px;
  width: 20px;
  height: 20px;
  border-radius: var(--radius-sm);
  background: #eef3ef;
  color: var(--c-primary);
  font-size: 12px;
  font-weight: 700;
  font-family: var(--font-mono);
  display: flex;
  align-items: center;
  justify-content: center;
}

.step-list-alt .step-item::before {
  background: #fbeade;
  color: #a5561c;
}

/* 整理记录速览 */
.log-groups {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
}

.log-group {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 16px 18px;
  min-width: 0;
}

.log-month {
  font-size: 15px;
  font-weight: 700;
  color: var(--c-primary);
  padding-bottom: 10px;
  margin-bottom: 10px;
  border-bottom: 1px solid var(--c-line-soft);
}

.log-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.log-item {
  position: relative;
  padding-left: 14px;
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
}

.log-item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 10px;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--c-info);
}

/* 站内栏目索引 */
.index-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
}

.index-card {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 18px;
  min-width: 0;
}

.index-card:hover,
.index-card:focus-within {
  border-color: #c3d3c8;
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.index-name {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 8px;
}

.index-name a {
  color: inherit;
}

.index-name a:hover,
.index-name a:focus-visible {
  color: var(--c-accent);
}

.index-desc {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
}

/* --------------------------------------------------------------------------
   pages · 频道分类 / 专题片单 / 观看指引 / 问题反馈 / 404
   -------------------------------------------------------------------------- */

/* 通用主内容 + 右侧栏 */
.page-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 30px;
  align-items: start;
}

.page-content,
.layout-main {
  min-width: 0;
}

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

/* 频道分类 */
.page-channels .section-channel-table .table-scroll {
  margin-bottom: 20px;
}

.figure-channel {
  margin-top: 20px;
  border: 1px solid var(--c-line);
}

.figure-channel img {
  aspect-ratio: 16 / 7;
}

.direction-group {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 16px 18px;
}

.direction-group + .direction-group {
  margin-top: 14px;
}

.direction-heading {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 8px;
}

.direction-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
}

.section-channel-topics .section-desc a {
  color: var(--c-primary);
  border-bottom: 1px solid #c6d5cc;
}

.section-channel-topics .section-desc a:hover,
.section-channel-topics .section-desc a:focus-visible {
  color: var(--c-accent);
  border-color: var(--c-accent);
}

.boundary-table {
  min-width: 0;
  font-size: 14px;
}

.boundary-table tbody th,
.boundary-table tbody td {
  padding: 10px 0;
  border-bottom: 1px solid var(--c-line-soft);
}

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

.boundary-table tbody th {
  width: 40%;
  color: var(--c-primary);
  font-weight: 600;
  white-space: normal;
}

.boundary-table tbody td {
  color: var(--c-muted);
}

/* 专题片单 */
.topic-feature {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr);
  gap: 24px;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  overflow: hidden;
}

.topic-feature-media {
  border-radius: 0;
  height: 100%;
}

.topic-feature-media img {
  aspect-ratio: 4 / 3;
  height: 100%;
}

.topic-feature-body {
  padding: 22px 22px 22px 0;
  min-width: 0;
}

.topic-feature-tag {
  display: inline-block;
  padding: 3px 10px;
  border-radius: var(--radius-sm);
  background: #fbeade;
  color: #a5561c;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 12px;
}

.topic-feature-name {
  font-size: 20px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 12px;
}

.topic-feature-scope,
.topic-feature-logic {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
  margin-bottom: 10px;
}

.topic-feature-points {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin: 14px 0 16px;
}

.topic-point {
  position: relative;
  padding-left: 18px;
  color: var(--c-text);
  font-size: 14px;
  line-height: 1.8;
}

.topic-point::before {
  content: "";
  position: absolute;
  left: 0;
  top: 9px;
  width: 7px;
  height: 7px;
  border-radius: 2px;
  background: var(--c-primary);
}

.topic-feature-link {
  margin-top: 4px;
}

.topic-archive-list {
  display: flex;
  flex-direction: column;
  gap: 0;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  overflow: hidden;
}

.topic-archive-item {
  padding: 16px 18px;
  border-bottom: 1px solid var(--c-line-soft);
  display: grid;
  grid-template-columns: 110px minmax(0, 1fr);
  grid-template-areas:
    "date name"
    "date summary";
  column-gap: 18px;
  row-gap: 6px;
}

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

.topic-archive-item:hover {
  background: #f8faf8;
}

.topic-archive-date {
  grid-area: date;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--c-muted);
  padding-top: 3px;
}

.topic-archive-name {
  grid-area: name;
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
}

.topic-archive-name a {
  color: inherit;
}

.topic-archive-name a:hover,
.topic-archive-name a:focus-visible {
  color: var(--c-accent);
}

.topic-archive-summary {
  grid-area: summary;
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
}

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

.related-card {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 18px;
  min-width: 0;
}

.related-card:hover,
.related-card:focus-within {
  border-color: #c3d3c8;
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.related-card-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 8px;
}

.related-card-title a {
  color: inherit;
}

.related-card-title a:hover,
.related-card-title a:focus-visible {
  color: var(--c-accent);
}

.related-card-desc {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  margin-bottom: 12px;
}

/* 观看指引 */
.guide-figure {
  border: 1px solid var(--c-line);
  margin-bottom: 30px;
}

.guide-figure img {
  aspect-ratio: 21 / 8;
}

.guide-prep,
.guide-check,
.guide-fields,
.guide-faq,
.guide-next {
  padding: 30px 0 0;
  margin-top: 30px;
  border-top: 1px solid var(--c-line-soft);
}

.guide-prep .section-desc,
.guide-check .section-desc,
.guide-fields .section-desc,
.guide-faq .section-desc,
.guide-next .section-desc {
  margin-bottom: 18px;
}

.prep-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 14px;
  counter-reset: prep;
}

.prep-item {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 14px 16px;
  counter-increment: prep;
}

.prep-index {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: var(--radius-sm);
  background: #eef3ef;
  color: var(--c-primary);
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.prep-index::before {
  content: counter(prep);
}

.prep-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
  min-width: 0;
}

.check-steps {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.check-step {
  display: flex;
  gap: 14px;
  align-items: flex-start;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-left: 3px solid var(--c-accent);
  border-radius: var(--radius);
  padding: 16px 18px;
}

.step-num {
  flex: 0 0 auto;
  width: 28px;
  height: 28px;
  border-radius: var(--radius-sm);
  background: var(--c-primary);
  color: #ffffff;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.step-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 6px;
}

.step-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
}

.fields-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(260px, 1fr);
  gap: 26px;
  align-items: start;
}

.fields-table-wrap {
  min-width: 0;
}

.fields-table {
  width: 100%;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  overflow: hidden;
  font-size: 14px;
}

.fields-table thead th {
  background: #f2f5f2;
  color: var(--c-primary);
  font-weight: 700;
  text-align: left;
  padding: 11px 14px;
  border-bottom: 1px solid var(--c-line);
  white-space: nowrap;
}

.fields-table tbody th,
.fields-table tbody td {
  padding: 11px 14px;
  border-bottom: 1px solid var(--c-line-soft);
  vertical-align: top;
  line-height: 1.75;
}

.fields-table tbody th {
  text-align: left;
  color: var(--c-primary);
  font-weight: 600;
  white-space: nowrap;
}

.fields-table tbody td {
  color: var(--c-muted);
}

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

.field-name {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--c-info);
}

.fields-boundary {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 18px;
  min-width: 0;
}

.boundary-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.boundary-item {
  padding-bottom: 12px;
  border-bottom: 1px solid var(--c-line-soft);
}

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

.boundary-label {
  display: inline-block;
  margin-bottom: 4px;
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  background: #eef3ef;
  color: var(--c-primary);
  font-size: 13px;
  font-weight: 600;
}

.boundary-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
}

.next-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 14px;
}

.next-link-item a {
  display: block;
  padding: 14px 16px;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  color: var(--c-primary);
  font-size: 15px;
  font-weight: 600;
}

.next-link-item a:hover,
.next-link-item a:focus-visible {
  border-color: var(--c-accent);
  color: var(--c-accent);
  transform: translateY(-1px);
  transition: transform 0.18s ease, border-color 0.18s ease, color 0.18s ease;
}

/* 问题反馈 */
.feedback-layout {
  grid-template-columns: minmax(0, 1fr) 320px;
}

.feedback-media {
  border: 1px solid var(--c-line);
  margin-bottom: 26px;
}

.feedback-media img {
  aspect-ratio: 16 / 7;
}

.content-section {
  padding: 26px 0 0;
  margin-top: 26px;
  border-top: 1px solid var(--c-line-soft);
}

.content-section:first-of-type {
  padding-top: 0;
  margin-top: 0;
  border-top: 0;
}

.content-section .section-desc {
  margin-bottom: 16px;
}

.faq-group + .faq-group {
  margin-top: 22px;
}

.faq-group-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 12px;
  padding-left: 10px;
  border-left: 3px solid var(--c-accent);
}

.faq-group .faq-item + .faq-item {
  margin-top: 10px;
}

.pending-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 14px;
}

.pending-item {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 14px 16px;
}

.pending-tag {
  display: inline-block;
  margin-bottom: 8px;
  padding: 2px 9px;
  border-radius: var(--radius-sm);
  background: #e8f0f9;
  color: var(--c-info);
  font-size: 13px;
  font-weight: 600;
}

.pending-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.8;
}

.ask-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
  counter-reset: ask;
}

.ask-item {
  position: relative;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 16px 18px 16px 54px;
  counter-increment: ask;
}

.ask-item::before {
  content: counter(ask);
  position: absolute;
  left: 18px;
  top: 17px;
  width: 24px;
  height: 24px;
  border-radius: var(--radius-sm);
  background: #eef3ef;
  color: var(--c-primary);
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.ask-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 6px;
}

.ask-text {
  color: var(--c-muted);
  font-size: 14px;
  line-height: 1.85;
}

.feedback-aside .aside-block + .aside-block {
  margin-top: 18px;
}

/* 404 */
.error-main {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 60px var(--shell-pad) 70px;
}

.error-block {
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 40px 32px;
  text-align: left;
}

.error-code {
  font-family: var(--font-mono);
  font-size: 44px;
  font-weight: 700;
  color: var(--c-accent);
  line-height: 1;
  margin-bottom: 14px;
}

.error-title {
  font-size: 26px;
  font-weight: 700;
  color: var(--c-primary);
  margin-bottom: 12px;
}

.error-desc {
  max-width: 620px;
  color: var(--c-muted);
  font-size: 15px;
  line-height: 1.85;
  margin-bottom: 22px;
}

.error-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.error-hint {
  margin-top: 30px;
}

.error-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
}

.error-links a {
  display: block;
  padding: 14px 16px;
  background: var(--c-card);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  color: var(--c-primary);
  font-size: 15px;
  font-weight: 600;
}

.error-links a:hover,
.error-links a:focus-visible {
  border-color: var(--c-accent);
  color: var(--c-accent);
}

/* --------------------------------------------------------------------------
   responsive · 断点
   -------------------------------------------------------------------------- */
@media (max-width: 1024px) {
  .hero {
    grid-template-columns: minmax(0, 1fr);
    gap: 26px;
  }

  .page-layout,
  .feedback-layout {
    grid-template-columns: minmax(0, 1fr) 300px;
    gap: 24px;
  }

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

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

@media (max-width: 900px) {
  .footer-inner {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 24px;
  }

  .footer-desc {
    max-width: none;
  }
}

@media (max-width: 768px) {
  .header-inner {
    height: 60px;
    gap: 12px;
  }

  .nav-toggle {
    display: flex;
  }

  .site-nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    margin-left: 0;
    background: #ffffff;
    border-bottom: 1px solid var(--c-line);
    box-shadow: var(--shadow-md);
    padding: 8px var(--shell-pad) 16px;
  }

  .nav-list {
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
  }

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

  .nav-link {
    width: 100%;
    justify-content: flex-start;
    padding: 0 12px;
    font-size: 16px;
  }

  .hero {
    padding-top: 28px;
    padding-bottom: 26px;
  }

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

  .topic-grid,
  .guide-columns,
  .related-grid,
  .fields-layout,
  .page-layout,
  .feedback-layout {
    grid-template-columns: minmax(0, 1fr);
  }

  .page-aside,
  .layout-aside {
    margin-top: 4px;
  }

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

  .topic-feature-body {
    padding: 0 18px 20px;
  }

  .topic-feature-media img {
    aspect-ratio: 16 / 9;
    height: auto;
  }

  .topic-archive-item {
    grid-template-columns: minmax(0, 1fr);
    grid-template-areas:
      "date"
      "name"
      "summary";
    row-gap: 4px;
  }

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

  .section {
    padding: 30px 0;
  }

  .inner-main {
    padding-bottom: 40px;
  }

  .page-title {
    font-size: 22px;
  }

  .error-block {
    padding: 28px 20px;
  }

  .error-code {
    font-size: 36px;
  }
}

@media (max-width: 480px) {
  :root {
    --shell-pad: 16px;
  }

  .topbar-text {
    font-size: 12px;
    text-align: left;
  }

  .brand-name {
    font-size: 16px;
  }

  .hero-title {
    font-size: 23px;
  }

  .hero-actions .btn {
    flex: 1 1 auto;
  }

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

  .prep-list,
  .pending-list,
  .next-links,
  .error-links {
    grid-template-columns: minmax(0, 1fr);
  }

  .footer-inner {
    grid-template-columns: minmax(0, 1fr);
    padding-top: 30px;
  }

  .data-table {
    min-width: 520px;
  }

  .ask-item {
    padding-left: 18px;
    padding-top: 46px;
  }

  .ask-item::before {
    top: 14px;
  }

  .mobile-bar {
    display: flex;
    position: sticky;
    bottom: 0;
    z-index: 30;
    background: #ffffff;
    border-top: 1px solid var(--c-line);
    padding-bottom: env(safe-area-inset-bottom, 0px);
  }

  .mobile-link {
    flex: 1 1 0;
    min-height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    color: var(--c-muted);
    border-right: 1px solid var(--c-line-soft);
  }

  .mobile-link:last-child {
    border-right: 0;
  }

  .mobile-link.is-current {
    color: var(--c-primary);
    font-weight: 700;
  }

  .site-footer {
    margin-bottom: 0;
  }
}

/* 滚动出现动画：仅增强，不影响初始可见 */
@media (prefers-reduced-motion: no-preference) {
  .topic-card,
  .index-card,
  .related-card {
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  }
}