/* ==========================================================================
   base — 基础变量、重置、全局排版
   ========================================================================== */

:root {
  --color-bg: #1a1a1a;
  --color-surface: #242424;
  --color-surface-raised: #2e2e2e;
  --color-text: #f5f5f5;
  --color-text-muted: #b8b8b8;
  --color-accent: #ffcc00;
  --color-link: #4db8ff;
  --color-danger: #e60000;
  --color-border: #3d3d3d;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB",
    "Microsoft YaHei", sans-serif;
  --container-width: 1200px;
  --radius-sm: 4px;
  --radius-md: 8px;
  --transition-fast: 0.15s ease;
  --transition-slow: 0.3s ease;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  line-height: 1.7;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-family);
  font-size: 1rem;
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

a {
  color: var(--color-link);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-accent);
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

ul,
ol {
  list-style-position: inside;
}

h1,
h2,
h3,
h4 {
  font-weight: 700;
  line-height: 1.3;
}

h1 {
  font-size: 2rem;
}

h2 {
  font-size: 1.5rem;
}

h3 {
  font-size: 1.125rem;
}

p {
  margin-bottom: 1rem;
}

time {
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

/* ==========================================================================
   layout — 容器、页头、页脚、内页布局骨架
   ========================================================================== */

.site-body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.site-header {
  background-color: #111111;
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 24px;
  height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand-logo {
  font-size: 1.375rem;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.brand-logo:hover {
  color: var(--color-accent);
}

.site-nav .nav-list {
  display: flex;
  align-items: center;
  gap: 8px;
  list-style: none;
}

.nav-item a {
  display: inline-block;
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.9375rem;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.nav-item a:hover {
  color: var(--color-text);
  background-color: var(--color-surface-raised);
}

.nav-item.is-current a,
.nav-item a.is-current {
  color: var(--color-accent);
  font-weight: 600;
  background-color: rgba(255, 204, 0, 0.08);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 10px;
  width: 44px;
  height: 44px;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
}

.nav-toggle-bar {
  display: block;
  width: 22px;
  height: 2px;
  background-color: var(--color-text);
  border-radius: 2px;
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}

.site-main {
  flex: 1 0 auto;
  width: 100%;
}

.home-main {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 24px;
}

.inner-main {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 24px;
}

.site-footer {
  background-color: #111111;
  border-top: 1px solid var(--color-border);
  margin-top: 48px;
}

.footer-inner {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 40px 24px 24px;
  display: flex;
  justify-content: space-between;
  gap: 48px;
}

.footer-brand {
  max-width: 360px;
}

.footer-site-name {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 8px;
}

.footer-brand p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  line-height: 1.6;
}

.footer-links {
  display: flex;
  gap: 48px;
}

.footer-col h3 {
  font-size: 0.9375rem;
  color: var(--color-text);
  margin-bottom: 12px;
}

.footer-col ul {
  list-style: none;
}

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

.footer-col a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.875rem;
}

.footer-col a:hover {
  color: var(--color-accent);
}

.footer-bottom {
  border-top: 1px solid var(--color-border);
  padding: 16px 24px;
  text-align: center;
}

.footer-bottom p {
  color: var(--color-text-muted);
  font-size: 0.8125rem;
  margin: 0;
}

/* 内页布局：主内容 + 右侧辅助栏 */
.page-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 40px;
  align-items: start;
  padding: 24px 0 0;
}

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

.page-layout .sidebar {
  min-width: 0;
}

/* 侧栏在前的变体（DOM 中 sidebar 在 main 之前时使用） */
.sidebar-left .page-layout {
  grid-template-columns: 320px minmax(0, 1fr);
}

/* channels 页使用 body 直接子元素结构 */
body.page-channels {
  display: block;
}

body.page-channels > .page-layout {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 24px 24px 0;
}

/* ==========================================================================
   components — 通用组件：面包屑、按钮、卡片、列表、FAQ
   ========================================================================== */

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 12px;
  list-style: none;
}

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

.breadcrumb a:hover {
  color: var(--color-accent);
}

.breadcrumb-sep {
  color: var(--color-text-muted);
  user-select: none;
}

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

.page-header {
  margin-bottom: 32px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--color-border);
}

.page-title {
  font-size: 1.875rem;
  color: var(--color-text);
  margin-bottom: 8px;
}

.page-description {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  max-width: 720px;
  margin: 0;
}

.btn-primary {
  display: inline-block;
  padding: 12px 28px;
  background-color: var(--color-accent);
  color: #1a1a1a;
  font-weight: 700;
  font-size: 0.9375rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  border: none;
  cursor: pointer;
  transition: background-color var(--transition-fast), transform var(--transition-fast);
  min-height: 44px;
  line-height: 1.4;
}

.btn-primary:hover {
  background-color: #e6b800;
  color: #1a1a1a;
  transform: translateY(-1px);
}

.section-title {
  font-size: 1.375rem;
  margin-bottom: 12px;
}

.content-section {
  margin-bottom: 40px;
}

/* 表单与输入（如有） */
input,
textarea,
select {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  color: var(--color-text);
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  font-family: var(--font-family);
  font-size: 0.9375rem;
  width: 100%;
}

input:focus,
textarea:focus,
select:focus {
  outline: 2px solid var(--color-accent);
  border-color: var(--color-accent);
}

/* ==========================================================================
   components — 首页模块
   ========================================================================== */

.hero-section {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(0, 0.9fr);
  gap: 48px;
  align-items: center;
  padding: 56px 0 48px;
}

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

.hero-content h1 {
  font-size: 2.375rem;
  line-height: 1.25;
  margin-bottom: 12px;
}

.hero-slogan {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-accent);
  margin-bottom: 12px;
}

.hero-description {
  color: var(--color-text-muted);
  margin-bottom: 24px;
}

.hero-figure {
  margin: 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  background-color: var(--color-surface);
}

.hero-figure img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

/* 频道快讯 */
.channels-section {
  padding: 40px 0;
  border-top: 1px solid var(--color-border);
}

.section-intro {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 20px;
  max-width: 680px;
}

.channel-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.channel-tag {
  display: inline-block;
  padding: 10px 20px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 999px;
  color: var(--color-text);
  font-size: 0.9375rem;
  font-weight: 600;
  text-decoration: none;
  transition: border-color var(--transition-fast), color var(--transition-fast), background-color var(--transition-fast);
}

.channel-tag:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  background-color: rgba(255, 204, 0, 0.05);
}

/* 深度内容 */
.latest-section {
  padding: 40px 0;
  border-top: 1px solid var(--color-border);
}

.article-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.article-item {
  padding: 20px 0;
  border-bottom: 1px solid var(--color-border);
}

.article-item:first-child {
  padding-top: 0;
}

.article-item:last-child {
  border-bottom: none;
}

.article-item h3 {
  margin-bottom: 6px;
}

.article-item h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.article-item h3 a:hover {
  color: var(--color-accent);
}

.article-summary {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 8px;
}

/* 专题推荐 */
.topics-section {
  padding: 40px 0;
  border-top: 1px solid var(--color-border);
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
}

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

.topic-card img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.topic-card h3 {
  padding: 16px 16px 0;
}

.topic-card h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.topic-card h3 a:hover {
  color: var(--color-accent);
}

.topic-card p {
  padding: 8px 16px 16px;
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin: 0;
}

/* 编辑推荐 */
.editor-picks {
  padding: 40px 0;
  border-top: 1px solid var(--color-border);
}

.pick-list {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 24px;
}

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

.pick-item h3 {
  margin-bottom: 8px;
}

.pick-item h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.pick-item h3 a:hover {
  color: var(--color-accent);
}

.pick-reason {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  margin: 0;
}

/* 信息来源说明 */
.source-note {
  padding: 40px 0;
  border-top: 1px solid var(--color-border);
  max-width: 720px;
}

.source-note h2 {
  font-size: 1.25rem;
  margin-bottom: 12px;
}

.text-link {
  color: var(--color-link);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.text-link:hover {
  color: var(--color-accent);
}

/* ==========================================================================
   components — channels 页（频道分类）
   ========================================================================== */

.channels-list-section {
  margin-bottom: 48px;
}

.channels-list {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.channel-item {
  display: grid;
  grid-template-columns: 180px minmax(0, 1fr);
  gap: 24px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 16px;
  align-items: center;
}

.channel-media {
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.channel-media img {
  width: 100%;
  aspect-ratio: 4 / 3;
  object-fit: cover;
}

.channel-body h3 {
  margin-bottom: 6px;
}

.channel-body h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.channel-body h3 a:hover {
  color: var(--color-accent);
}

.channel-body p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 8px;
}

.channel-body a {
  font-size: 0.875rem;
  font-weight: 600;
}

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

.intro-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px;
}

.intro-card h3 {
  font-size: 1rem;
  margin-bottom: 8px;
  color: var(--color-accent);
}

.intro-card p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  margin: 0;
}

.related-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 16px;
  margin-top: 32px;
  padding: 16px;
  background-color: var(--color-surface);
  border-radius: var(--radius-sm);
}

.related-links-label {
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--color-text);
}

.related-links-item {
  font-size: 0.875rem;
  color: var(--color-link);
  text-decoration: none;
}

.related-links-item:hover {
  color: var(--color-accent);
}

/* 侧栏 */
.content-sidebar {
  min-width: 0;
}

.sidebar-block {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px;
  margin-bottom: 20px;
}

.sidebar-block h2 {
  font-size: 1rem;
  color: var(--color-text);
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border);
}

.sidebar-links {
  list-style: none;
}

.sidebar-links li {
  margin-bottom: 10px;
}

.sidebar-links a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.875rem;
  display: inline-block;
}

.sidebar-links a:hover {
  color: var(--color-accent);
}

/* ==========================================================================
   components — topics 页（内容专题）
   ========================================================================== */

.featured-topics-section {
  margin-bottom: 40px;
}

.featured-topics-section > h2 {
  font-size: 1.375rem;
  margin-bottom: 20px;
}

.featured-topics-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
}

.featured-topic-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.topic-figure {
  margin: 0;
  overflow: hidden;
}

.topic-figure img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.topic-card-body {
  padding: 20px;
  flex: 1;
  display: flex;
  flex-direction: column;
}

.topic-card-body h3 {
  margin-bottom: 8px;
}

.topic-card-body h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.topic-card-body h3 a:hover {
  color: var(--color-accent);
}

.topic-card-body p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 12px;
}

.topic-card-body a {
  margin-top: auto;
  font-size: 0.875rem;
  font-weight: 600;
}

.topic-list-section {
  margin-bottom: 40px;
}

.topic-list-section > h2 {
  font-size: 1.375rem;
  margin-bottom: 20px;
}

.topic-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.topic-list-item {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 16px;
  padding: 20px 0;
  border-bottom: 1px solid var(--color-border);
  align-items: start;
}

.topic-list-item:first-child {
  padding-top: 0;
}

.topic-list-item:last-child {
  border-bottom: none;
}

.topic-item-text h3 {
  margin-bottom: 6px;
}

.topic-item-text h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.topic-item-text h3 a:hover {
  color: var(--color-accent);
}

.topic-item-text p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 8px;
}

.topic-item-text time {
  display: block;
  margin-bottom: 8px;
}

.topic-item-text a {
  font-size: 0.875rem;
  font-weight: 600;
}

.related-reading-section {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px;
  margin-bottom: 40px;
}

.related-reading-section h2 {
  font-size: 1.125rem;
  margin-bottom: 8px;
}

.related-reading-section > p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  margin-bottom: 16px;
}

.related-links {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 24px;
}

.related-links li a {
  color: var(--color-link);
  text-decoration: none;
  font-size: 0.875rem;
}

.related-links li a:hover {
  color: var(--color-accent);
}

/* ==========================================================================
   components — guide 页（实用指南）
   ========================================================================== */

.guide-section {
  margin-bottom: 40px;
}

.guide-section h2 {
  font-size: 1.375rem;
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border);
}

.guide-section > p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 20px;
}

.guide-steps {
  list-style: none;
  counter-reset: guide-step;
  margin-bottom: 20px;
}

.guide-steps li {
  position: relative;
  padding: 16px 16px 16px 56px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  margin-bottom: 12px;
  counter-increment: guide-step;
}

.guide-steps li::before {
  content: counter(guide-step);
  position: absolute;
  left: 16px;
  top: 16px;
  width: 28px;
  height: 28px;
  background-color: var(--color-accent);
  color: #1a1a1a;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.875rem;
}

.guide-steps h3 {
  font-size: 1rem;
  margin-bottom: 6px;
}

.guide-steps p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  margin: 0;
}

.guide-media {
  margin: 24px 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  background-color: var(--color-surface);
}

.guide-media img {
  width: 100%;
  aspect-ratio: 16 / 7;
  object-fit: cover;
}

.guide-media figcaption {
  padding: 12px 16px;
  color: var(--color-text-muted);
  font-size: 0.875rem;
  background-color: var(--color-surface);
}

.related-links h3 {
  font-size: 1.125rem;
  margin-bottom: 12px;
}

.related-links ul {
  list-style: none;
}

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

.related-links ul li a {
  color: var(--color-link);
  text-decoration: none;
  font-size: 0.875rem;
}

.related-links ul li a:hover {
  color: var(--color-accent);
}

/* 侧栏 */
.sidebar-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px;
  margin-bottom: 20px;
}

.sidebar-card h2,
.sidebar-card h3 {
  font-size: 1rem;
  color: var(--color-text);
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border);
}

.sidebar-list {
  list-style: none;
}

.sidebar-list li {
  margin-bottom: 10px;
}

.sidebar-list a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.875rem;
  display: inline-block;
}

.sidebar-list a:hover {
  color: var(--color-accent);
}

/* ==========================================================================
   components — faq 页（常见问题）
   ========================================================================== */

.layout-shell {
  width: 100%;
}

.faq-section {
  margin-bottom: 40px;
}

.faq-section h2 {
  font-size: 1.375rem;
  margin-bottom: 8px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border);
}

.faq-section > p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 16px;
}

.faq-item {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  margin-bottom: 12px;
  overflow: hidden;
}

.faq-item summary {
  padding: 16px 20px;
  font-weight: 600;
  font-size: 0.9375rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  transition: background-color var(--transition-fast);
}

.faq-item summary:hover {
  background-color: var(--color-surface-raised);
}

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

.faq-item summary::after {
  content: "+";
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--color-accent);
  flex-shrink: 0;
  transition: transform var(--transition-fast);
}

.faq-item[open] summary::after {
  transform: rotate(45deg);
}

.faq-answer {
  padding: 0 20px 16px;
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  border-top: 1px solid var(--color-border);
  padding-top: 12px;
}

.faq-answer p {
  margin-bottom: 8px;
}

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

.faq-media {
  margin: 24px 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  background-color: var(--color-surface);
}

.faq-media img {
  width: 100%;
  aspect-ratio: 16 / 7;
  object-fit: cover;
}

.faq-media figcaption {
  padding: 12px 16px;
  color: var(--color-text-muted);
  font-size: 0.875rem;
  background-color: var(--color-surface);
}

.usage-steps {
  list-style: decimal;
  padding-left: 20px;
  margin-bottom: 16px;
}

.usage-steps li {
  margin-bottom: 6px;
  font-size: 0.9375rem;
}

.update-list {
  list-style: disc;
  padding-left: 20px;
  margin-bottom: 12px;
}

.update-list li {
  margin-bottom: 6px;
  font-size: 0.9375rem;
  color: var(--color-text-muted);
}

/* ==========================================================================
   pages — 404 错误页
   ========================================================================== */

.error-main {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 80px 24px;
  flex: 1 0 auto;
}

.error-section {
  text-align: center;
  max-width: 560px;
}

.error-code {
  font-size: 5rem;
  font-weight: 800;
  color: var(--color-accent);
  line-height: 1;
  margin-bottom: 8px;
}

.error-title {
  font-size: 1.75rem;
  margin-bottom: 16px;
}

.error-desc {
  color: var(--color-text-muted);
  margin-bottom: 24px;
}

.error-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.error-btn-home,
.error-btn-channels {
  display: inline-block;
  padding: 12px 28px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.9375rem;
  text-decoration: none;
  min-height: 44px;
  line-height: 1.4;
}

.error-btn-home {
  background-color: var(--color-accent);
  color: #1a1a1a;
}

.error-btn-home:hover {
  background-color: #e6b800;
  color: #1a1a1a;
}

.error-btn-channels {
  background-color: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.error-btn-channels:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.error-help {
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

/* ==========================================================================
   responsive — 响应式断点
   ========================================================================== */

@media (max-width: 1024px) {
  .page-layout {
    grid-template-columns: minmax(0, 1fr) 280px;
    gap: 24px;
  }

  .sidebar-left .page-layout {
    grid-template-columns: 280px minmax(0, 1fr);
  }

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

  .pick-item:last-child {
    grid-column: 1 / -1;
  }
}

@media (max-width: 768px) {
  .header-inner {
    height: auto;
    min-height: 60px;
    padding: 8px 16px;
    flex-wrap: wrap;
    position: relative;
  }

  .nav-toggle {
    display: flex;
    order: 3;
  }

  .site-nav {
    order: 4;
    flex-basis: 100%;
  }

  .site-nav .nav-list {
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 8px 0 12px;
    width: 100%;
  }

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

  .nav-item a {
    display: block;
    padding: 12px 16px;
    border-radius: var(--radius-sm);
  }

  .nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
  }

  .nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(2) {
    opacity: 0;
  }

  .nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
  }

  /* 首页 */
  .hero-section {
    grid-template-columns: 1fr;
    gap: 24px;
    padding: 32px 0;
  }

  .hero-content h1 {
    font-size: 1.75rem;
  }

  .topic-grid {
    grid-template-columns: 1fr;
  }

  .pick-list {
    grid-template-columns: 1fr;
  }

  .pick-item:last-child {
    grid-column: auto;
  }

  /* 内页布局 */
  .page-layout {
    grid-template-columns: 1fr;
    gap: 0;
  }

  .sidebar-left .page-layout {
    grid-template-columns: 1fr;
  }

  .page-layout .sidebar,
  .page-layout .main-content {
    width: 100%;
  }

  .page-layout .sidebar {
    margin-top: 32px;
  }

  /* channels */
  .channel-item {
    grid-template-columns: 1fr;
    gap: 16px;
  }

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

  .channel-intro-grid {
    grid-template-columns: 1fr;
  }

  /* topics */
  .featured-topics-grid {
    grid-template-columns: 1fr;
  }

  .topic-list-item {
    grid-template-columns: 1fr;
    gap: 8px;
  }

  /* faq */
  .faq-item summary {
    padding: 14px 16px;
  }

  .faq-answer {
    padding: 0 16px 14px;
  }

  /* footer */
  .footer-inner {
    flex-direction: column;
    gap: 24px;
    padding: 32px 16px 16px;
  }

  .footer-links {
    flex-direction: column;
    gap: 24px;
  }

  .footer-bottom {
    padding: 12px 16px;
  }

  .home-main,
  .inner-main,
  body.page-channels > .page-layout {
    padding-left: 16px;
    padding-right: 16px;
  }
}

@media (max-width: 480px) {
  .hero-content h1 {
    font-size: 1.5rem;
  }

  .error-code {
    font-size: 3.5rem;
  }

  .error-title {
    font-size: 1.375rem;
  }

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

  .error-btn-home,
  .error-btn-channels {
    text-align: center;
  }
}

/* ==========================================================================
   utilities — 辅助与无障碍
   ========================================================================== */

:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}