/* ============================================================
   BASE — 全局基础样式
   ============================================================ */
:root {
  --color-bg: #f5f7fa;
  --color-surface: #ffffff;
  --color-text: #1e293b;
  --color-text-secondary: #475569;
  --color-text-muted: #64748b;
  --color-primary: #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-accent: #10b981;
  --color-border: #e2e8f0;
  --color-code-bg: #f1f5f9;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: "Courier New", Courier, monospace;
  --container-width: 1200px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --shadow-sm: 0 1px 2px rgba(30, 41, 59, 0.06);
  --shadow-md: 0 2px 8px rgba(30, 41, 59, 0.08);
  --shadow-lg: 0 4px 16px rgba(30, 41, 59, 0.1);
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

ul,
ol {
  list-style: none;
}

h1,
h2,
h3,
h4 {
  font-family: var(--font-mono);
  line-height: 1.3;
  color: var(--color-text);
}

h1 {
  font-size: 2rem;
  font-weight: 700;
}

h2 {
  font-size: 1.5rem;
  font-weight: 700;
}

h3 {
  font-size: 1.125rem;
  font-weight: 600;
}

h4 {
  font-size: 1rem;
  font-weight: 600;
}

p {
  margin-bottom: 0.75rem;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

input {
  font-family: inherit;
}

.section-title {
  font-size: 1.375rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-primary);
  display: inline-block;
}

/* ============================================================
   LAYOUT — 全站统一骨架
   ============================================================ */
.site-header {
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-shell {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 1.25rem;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}

.brand-link {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  white-space: nowrap;
  letter-spacing: 0.02em;
}

.brand-link:hover {
  color: var(--color-primary);
}

.site-nav {
  display: flex;
  align-items: center;
}

.nav-toggle {
  display: none;
  width: 44px;
  height: 44px;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-surface);
}

.nav-toggle-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-list li a {
  display: block;
  padding: 0.5rem 0.875rem;
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.nav-list li a:hover {
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.06);
}

.nav-list li a.is-current {
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.1);
  font-weight: 600;
}

.lang-switch {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  white-space: nowrap;
  border: 1px solid var(--color-border);
  padding: 0.25rem 0.625rem;
  border-radius: var(--radius-sm);
  background-color: var(--color-code-bg);
}

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

.site-footer {
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border);
  margin-top: 3rem;
}

.footer-shell {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 2.5rem 1.25rem 1.5rem;
  display: grid;
  grid-template-columns: 1.2fr 2fr;
  gap: 2.5rem;
}

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

.footer-sitename {
  font-family: var(--font-mono);
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 0.5rem;
}

.footer-desc {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  line-height: 1.7;
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.footer-col h4 {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 0.875rem;
}

.footer-col ul li {
  margin-bottom: 0.5rem;
}

.footer-col ul li a {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
}

.footer-col ul li a:hover {
  color: var(--color-primary);
}

.copyright {
  grid-column: 1 / -1;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  border-top: 1px solid var(--color-border);
  padding-top: 1.25rem;
  margin-top: 1rem;
  text-align: center;
}

/* 内页统一骨架 */
.inner-main {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 1.5rem 1.25rem 3rem;
  width: 100%;
  flex: 1;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 1.5rem;
}

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

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

.breadcrumb-sep {
  color: var(--color-border);
  font-family: var(--font-mono);
}

.breadcrumb-current {
  color: var(--color-text);
  font-weight: 500;
}

.page-header {
  margin-bottom: 2rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--color-border);
}

.page-title {
  font-size: 1.875rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 0.625rem;
}

.page-description {
  font-size: 1rem;
  color: var(--color-text-secondary);
  max-width: 720px;
  line-height: 1.7;
}

/* ============================================================
   COMPONENTS — 通用组件
   ============================================================ */
/* 首页公告条 */
.notice-bar {
  background-color: var(--color-primary);
  color: #ffffff;
  padding: 0.5rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  position: relative;
}

.notice-text {
  font-size: 0.875rem;
  line-height: 1.5;
}

.notice-close {
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #ffffff;
  font-size: 1.25rem;
  border-radius: var(--radius-sm);
  position: absolute;
  right: 1rem;
  top: 50%;
  transform: translateY(-50%);
}

.notice-close:hover {
  background-color: rgba(255, 255, 255, 0.2);
}

/* 首页 Hero 区 */
.hero-section {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 3rem 1.25rem 2.5rem;
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 2.5rem;
  align-items: center;
}

.hero-title {
  font-size: 2.25rem;
  font-weight: 700;
  line-height: 1.25;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}

.hero-tagline {
  font-family: var(--font-mono);
  font-size: 1.125rem;
  color: var(--color-accent);
  margin-bottom: 0.75rem;
  font-weight: 600;
}

.hero-desc {
  font-size: 1rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: 1.5rem;
  max-width: 560px;
}

.btn-primary {
  display: inline-block;
  background-color: var(--color-primary);
  color: #ffffff;
  font-size: 0.9375rem;
  font-weight: 600;
  padding: 0.75rem 1.75rem;
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

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

.hero-figure {
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--color-border);
  background-color: var(--color-code-bg);
}

.hero-figure img {
  width: 100%;
  height: 300px;
  object-fit: cover;
}

/* 首页频道标签条 */
.channel-strip {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 2rem 1.25rem;
}

.channel-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.tag-item {
  display: inline-block;
  padding: 0.5rem 1.125rem;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: border-color var(--transition-fast), color var(--transition-fast), background-color var(--transition-fast);
}

.tag-item:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.04);
}

/* 首页专题推荐 */
.topic-teaser {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 2rem 1.25rem;
}

.topic-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.topic-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-normal), transform var(--transition-normal);
}

.topic-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.topic-card img {
  width: 100%;
  height: 180px;
  object-fit: cover;
}

.topic-card h3 {
  padding: 1rem 1.25rem 0.25rem;
  font-size: 1.125rem;
}

.topic-card p {
  padding: 0 1.25rem;
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

.topic-card a {
  display: inline-block;
  margin: 0.5rem 1.25rem 1.25rem;
  font-size: 0.9375rem;
  font-weight: 500;
}

/* 首页最新视频列表 */
.latest-list {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 2rem 1.25rem;
}

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

.video-item {
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--color-border);
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.5rem 1rem;
  align-items: baseline;
}

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

.video-date {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  white-space: nowrap;
}

.video-item a {
  font-size: 1rem;
  font-weight: 500;
  color: var(--color-text);
}

.video-item a:hover {
  color: var(--color-primary);
}

.video-summary {
  grid-column: 2;
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 0;
  line-height: 1.5;
}

/* 首页观看指南入口 */
.guide-entry {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 2rem 1.25rem;
}

.guide-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.guide-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-normal);
}

.guide-card:hover {
  box-shadow: var(--shadow-md);
}

.guide-card h3 {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
}

.guide-card p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  margin-bottom: 1rem;
  line-height: 1.6;
}

.guide-card a {
  font-weight: 500;
  font-size: 0.9375rem;
}

/* 首页侧栏 */
.home-main {
  max-width: var(--container-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 0;
  align-items: start;
}

.sidebar {
  padding: 2rem 1.25rem;
}

.sidebar-block {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.sidebar-block h3 {
  font-size: 1rem;
  margin-bottom: 0.875rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-primary);
  display: inline-block;
}

.search-hint {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 0.75rem;
  line-height: 1.5;
}

.search-box {
  display: flex;
  gap: 0.5rem;
}

.search-box input {
  flex: 1;
  padding: 0.625rem 0.875rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: 0.9375rem;
  background-color: var(--color-surface);
  color: var(--color-text);
  min-height: 44px;
}

.search-box input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

/* ============================================================
   内页组件 — 频道分类页
   ============================================================ */
.channels-section,
.channel-details {
  margin-bottom: 2.5rem;
}

.section-intro {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  margin-bottom: 1.5rem;
  max-width: 720px;
  line-height: 1.7;
}

.channel-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.channel-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-normal), transform var(--transition-normal);
}

.channel-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.channel-thumb {
  width: 100%;
  height: 140px;
  object-fit: cover;
}

.channel-info {
  padding: 1.25rem;
}

.channel-info h3 {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
}

.channel-info p {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 0.75rem;
}

.channel-info a {
  font-size: 0.875rem;
  font-weight: 500;
}

.detail-list {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.detail-item {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.detail-item h3 {
  font-size: 1.0625rem;
  margin-bottom: 0.625rem;
  color: var(--color-primary);
}

.detail-item p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.65;
}

.related-links {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
}

.related-links h2 {
  font-size: 1.25rem;
  margin-bottom: 1rem;
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

.related-card {
  display: block;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.related-card:hover {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-md);
}

.related-card h3 {
  font-size: 1rem;
  margin-bottom: 0.375rem;
  color: var(--color-text);
}

.related-card p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 0;
  line-height: 1.5;
}

/* ============================================================
   内页组件 — 内容专题页
   ============================================================ */
.topic-module,
.playlist-module {
  margin-bottom: 2.5rem;
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.topic-figure {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

.topic-figure img {
  width: 100%;
  height: 200px;
  object-fit: cover;
}

.topic-title {
  font-size: 1.125rem;
  margin: 1rem 0 0.5rem;
}

.topic-summary {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 0.75rem;
}

.topic-link {
  font-weight: 500;
  font-size: 0.9375rem;
}

.playlist-block {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.playlist-block h3 {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
  color: var(--color-primary);
}

.playlist-reason {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 1.25rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--color-border);
}

.playlist-list {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem 1.5rem;
}

.playlist-list li {
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
  padding: 0.5rem 0;
  border-bottom: 1px dashed var(--color-border);
}

.playlist-title {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-text);
}

.playlist-note {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

/* ============================================================
   内页组件 — 观看指南页
   ============================================================ */
.guide-overview {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 2rem;
  margin-bottom: 2.5rem;
  align-items: start;
}

.overview-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-sm);
}

.overview-card h2 {
  font-size: 1.25rem;
  margin-bottom: 0.875rem;
}

.overview-card p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.overview-media {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

.guide-figure img {
  width: 100%;
  height: 200px;
  object-fit: cover;
}

.guide-figure figcaption {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  padding: 0.625rem 0.875rem;
  background-color: var(--color-code-bg);
}

.guide-section {
  margin-bottom: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
}

.guide-section>h2 {
  font-size: 1.375rem;
  margin-bottom: 0.625rem;
}

.guide-section>p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  margin-bottom: 1.5rem;
  max-width: 720px;
  line-height: 1.7;
}

.guide-steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.step-item {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  position: relative;
}

.step-item h3 {
  font-size: 1.0625rem;
  margin-bottom: 0.625rem;
  color: var(--color-primary);
}

.step-item p {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.65;
  margin-bottom: 0.5rem;
}

.guide-link {
  font-size: 0.9375rem;
}

.guide-link a {
  font-weight: 500;
  margin-right: 1.5rem;
}

.guide-tips {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-sm);
}

.guide-tips h2 {
  font-size: 1.25rem;
  margin-bottom: 0.625rem;
}

.guide-tips>p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  margin-bottom: 1.25rem;
}

.tips-list {
  margin-bottom: 1.25rem;
}

.tips-list li {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  padding: 0.5rem 0 0.5rem 1.5rem;
  position: relative;
  line-height: 1.6;
}

.tips-list li::before {
  content: ">";
  position: absolute;
  left: 0;
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-weight: 700;
}

/* ============================================================
   内页组件 — FAQ 页
   ============================================================ */
.faq-section {
  margin-bottom: 2.5rem;
}

.faq-section>h2 {
  font-size: 1.375rem;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-primary);
  display: inline-block;
}

.content-media {
  margin-bottom: 1.5rem;
}

.content-media-inline {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

.content-media-inline img {
  width: 100%;
  height: 160px;
  object-fit: cover;
}

.content-media-inline figcaption {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  padding: 0.625rem 0.875rem;
  background-color: var(--color-code-bg);
}

.faq-list {
  margin-bottom: 1.5rem;
}

.faq-item {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin-bottom: 0.75rem;
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.faq-item:hover {
  border-color: var(--color-primary);
}

.faq-item summary {
  padding: 1rem 1.25rem;
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-text);
  cursor: pointer;
  list-style: none;
  position: relative;
  padding-right: 2.5rem;
  min-height: 44px;
  display: flex;
  align-items: center;
}

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

.faq-item summary::after {
  content: "+";
  position: absolute;
  right: 1.25rem;
  font-family: var(--font-mono);
  font-size: 1.25rem;
  color: var(--color-primary);
  transition: transform var(--transition-fast);
}

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

.faq-answer {
  padding: 0 1.25rem 1rem;
  border-top: 1px solid var(--color-border);
  margin-top: 0.5rem;
}

.faq-answer p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-top: 0.75rem;
}

.help-entry {
  margin-top: 2.5rem;
}

.help-entry-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-sm);
}

.help-entry-card h2 {
  font-size: 1.25rem;
  margin-bottom: 0.625rem;
}

.help-entry-card>p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  margin-bottom: 1.25rem;
  line-height: 1.7;
}

.help-entry-card ul {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.5rem 1.5rem;
}

.help-entry-card ul li a {
  font-size: 0.9375rem;
  font-weight: 500;
  display: inline-block;
  padding: 0.375rem 0;
}

/* ============================================================
   内页组件 — 长尾主题文章页
   ============================================================ */
.article-content {
  max-width: 860px;
}

.content-section {
  margin-bottom: 2.5rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--color-border);
}

.content-section:last-of-type {
  border-bottom: none;
}

.section-figure {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
  margin-bottom: 1.25rem;
}

.section-figure img {
  width: 100%;
  height: 220px;
  object-fit: cover;
}

.section-figure figcaption {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  padding: 0.625rem 0.875rem;
  background-color: var(--color-code-bg);
}

.content-section p {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.8;
  margin-bottom: 1rem;
}

.feature-list {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.25rem;
}

.feature-list li {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  padding: 0.5rem 0;
  line-height: 1.7;
  position: relative;
  padding-left: 1.5rem;
}

.feature-list li::before {
  content: ">";
  position: absolute;
  left: 0;
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-weight: 700;
}

.feature-list li strong {
  color: var(--color-text);
  font-weight: 600;
}

.related-pages {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-top: 2.5rem;
  box-shadow: var(--shadow-sm);
}

.related-title {
  font-size: 1rem;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-primary);
  display: inline-block;
}

.related-list li {
  margin-bottom: 0.5rem;
}

.related-list li a {
  font-size: 0.9375rem;
  font-weight: 500;
  padding: 0.375rem 0;
  display: inline-block;
}

/* ============================================================
   404 页面
   ============================================================ */
.error-main {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 4rem 1.25rem;
  flex: 1;
}

.error-panel {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 3rem 2.5rem;
  text-align: center;
  max-width: 520px;
  width: 100%;
  box-shadow: var(--shadow-md);
}

.error-code {
  font-family: var(--font-mono);
  font-size: 3rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 0.5rem;
  line-height: 1.2;
}

.error-panel h1 {
  font-size: 1.375rem;
  margin-bottom: 0.875rem;
}

.error-desc {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: 1.5rem;
}

.error-btn {
  display: inline-block;
  background-color: var(--color-primary);
  color: #ffffff;
  font-size: 0.9375rem;
  font-weight: 600;
  padding: 0.75rem 1.75rem;
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

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

/* ============================================================
   RESPONSIVE — 响应式断点
   ============================================================ */
@media (max-width: 1024px) {
  .channel-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .guide-steps {
    grid-template-columns: repeat(2, 1fr);
  }

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

  .guide-overview {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .hero-section {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .hero-figure img {
    height: 240px;
  }

  .home-main {
    grid-template-columns: 1fr;
  }

  .sidebar {
    padding-top: 0;
  }
}

@media (max-width: 768px) {
  .header-shell {
    height: 56px;
    gap: 0.75rem;
  }

  .brand-link {
    font-size: 1.0625rem;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-list {
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    align-items: stretch;
    padding: 0.5rem;
    gap: 0.125rem;
    display: none;
    box-shadow: var(--shadow-md);
    z-index: 99;
  }

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

  .nav-list li a {
    padding: 0.75rem 1rem;
    font-size: 1rem;
  }

  .lang-switch {
    font-size: 0.75rem;
    padding: 0.25rem 0.5rem;
  }

  .inner-main {
    padding: 1.25rem 1rem 2.5rem;
  }

  .page-title {
    font-size: 1.5rem;
  }

  .hero-section {
    padding: 2rem 1rem 1.5rem;
  }

  .hero-title {
    font-size: 1.75rem;
  }

  .hero-figure img {
    height: 200px;
  }

  .channel-strip,
  .topic-teaser,
  .latest-list,
  .guide-entry {
    padding: 1.5rem 1rem;
  }

  .topic-cards,
  .guide-cards,
  .topic-grid,
  .playlist-list,
  .related-grid {
    grid-template-columns: 1fr;
  }

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

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

  .guide-steps {
    grid-template-columns: 1fr;
  }

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

  .footer-shell {
    grid-template-columns: 1fr;
    gap: 1.5rem;
    padding: 2rem 1rem 1.25rem;
  }

  .footer-links {
    grid-template-columns: repeat(2, 1fr);
  }

  .copyright {
    margin-top: 0.5rem;
  }

  .sidebar {
    padding: 1.5rem 1rem;
  }

  .help-entry-card ul {
    grid-template-columns: 1fr;
  }

  .error-panel {
    padding: 2.5rem 1.5rem;
  }

  .error-code {
    font-size: 2.25rem;
  }
}

@media (max-width: 480px) {
  .brand-link {
    font-size: 1rem;
  }

  .lang-switch {
    display: none;
  }

  .footer-links {
    grid-template-columns: 1fr;
    gap: 1.25rem;
  }

  .hero-title {
    font-size: 1.5rem;
  }

  .hero-tagline {
    font-size: 1rem;
  }

  .video-item {
    grid-template-columns: 1fr;
    gap: 0.25rem;
  }

  .video-summary {
    grid-column: 1;
  }

  .video-date {
    font-size: 0.75rem;
  }

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

  .section-title {
    font-size: 1.25rem;
  }

  .topic-card img {
    height: 160px;
  }

  .channel-thumb {
    height: 120px;
  }

  .content-media-inline img {
    height: 140px;
  }

  .section-figure img {
    height: 180px;
  }
}

/* 滚动出现动画（渐进增强，不影响初始可见性） */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (prefers-reduced-motion: no-preference) {
  .hero-section,
  .channel-strip,
  .topic-teaser,
  .latest-list,
  .guide-entry,
  .topic-module,
  .playlist-module,
  .guide-section,
  .faq-section,
  .content-section {
    animation: fadeInUp 0.4s ease both;
  }

  .topic-teaser {
    animation-delay: 0.05s;
  }

  .latest-list {
    animation-delay: 0.1s;
  }

  .guide-entry {
    animation-delay: 0.15s;
  }
}