/* ==========================================================
   免费吃瓜 · 整站样式表
   研究报告风 · 白灰主调 · 蓝绿点缀
   ========================================================== */

/* ==========================================================
   Base —— 变量、重置、全局基础
   ========================================================== */
:root {
  --color-bg: #f5f6fa;
  --color-surface: #ffffff;
  --color-text: #2c3e50;
  --color-text-light: #5d6d7e;
  --color-text-muted: #8a94a3;
  --color-border: #e3e7ee;
  --color-accent: #3498db;
  --color-accent-dark: #2a7fb8;
  --color-accent-soft: #eaf4fb;
  --color-orange: #e67e22;
  --color-orange-soft: #fdf3e7;
  --color-footer-bg: #243342;
  --color-footer-text: #aebccb;
  --color-footer-heading: #e8edf2;
  --font-body: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --container-width: 1140px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --shadow-sm: 0 1px 3px rgba(44, 62, 80, 0.08);
  --shadow-md: 0 2px 8px rgba(44, 62, 80, 0.1);
  --transition-base: 0.2s ease;
}

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

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

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

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

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

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

ul,
ol {
  list-style: none;
}

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

figure {
  margin: 0;
}

/* 通用容器 */
.site-body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  background-color: var(--color-bg);
}

/* ==========================================================
   Layout —— 页头、页脚、主容器、栅格骨架
   ========================================================== */

/* ---------- 页头（全站统一双层） ---------- */
.site-header {
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: relative;
  z-index: 100;
}

.header-top {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 14px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand-link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  color: var(--color-text);
}

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

.brand-name {
  font-size: 24px;
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: 0.5px;
}

.brand-slogan {
  font-size: 13px;
  color: var(--color-text-muted);
  font-weight: 400;
}

.quick-nav.site-nav a {
  font-size: 14px;
  color: var(--color-text-light);
  padding: 6px 14px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

.quick-nav.site-nav a:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.quick-nav.site-nav a.is-current {
  background-color: var(--color-accent-soft);
  border-color: var(--color-accent);
  color: var(--color-accent);
  font-weight: 600;
}

.header-bottom {
  border-top: 1px solid var(--color-border);
  background-color: var(--color-surface);
}

.header-bottom .site-nav {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 20px;
}

.nav-list {
  display: flex;
  list-style: none;
}

.nav-list li a {
  display: block;
  padding: 12px 20px;
  font-size: 15px;
  font-weight: 500;
  color: var(--color-text);
  border-bottom: 2px solid transparent;
  transition: all var(--transition-base);
}

.nav-list li a:hover {
  color: var(--color-accent);
  background-color: var(--color-accent-soft);
}

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

/* 汉堡按钮 —— 桌面隐藏 */
.nav-toggle {
  display: none;
}

/* ---------- 主容器 ---------- */
.site-main {
  flex: 1;
  width: 100%;
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 32px 20px 48px;
}

/* ---------- 页脚（全站统一四栏） ---------- */
.site-footer {
  background-color: var(--color-footer-bg);
  color: var(--color-footer-text);
  margin-top: auto;
}

.footer-columns {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 48px 20px 24px;
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1fr;
  gap: 40px;
}

.footer-brand {
  font-size: 20px;
  font-weight: 700;
  color: var(--color-footer-heading);
  margin-bottom: 10px;
}

.footer-desc {
  font-size: 14px;
  line-height: 1.6;
  color: var(--color-footer-text);
  max-width: 260px;
}

.footer-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-footer-heading);
  margin-bottom: 16px;
  letter-spacing: 0.5px;
}

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

.footer-links a {
  font-size: 14px;
  color: var(--color-footer-text);
}

.footer-links a:hover {
  color: var(--color-surface);
}

/* ---------- 面包屑（全站统一） ---------- */
.breadcrumb {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  font-size: 14px;
  color: var(--color-text-muted);
  margin-bottom: 24px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--color-border);
}

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

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

.breadcrumb-sep {
  color: var(--color-text-muted);
  margin: 0 2px;
}

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

/* ---------- 页面标题区（全站统一） ---------- */
.page-header {
  margin-bottom: 36px;
}

.page-title {
  font-size: 32px;
  font-weight: 800;
  line-height: 1.3;
  margin-bottom: 10px;
  color: var(--color-text);
}

.page-description {
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-text-light);
  max-width: 720px;
}

/* ---------- 通用 section 标题 ---------- */
.section-title {
  font-size: 22px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 16px;
  padding-left: 12px;
  border-left: 4px solid var(--color-accent);
  line-height: 1.4;
}

/* ---------- 阅读更多链接 ---------- */
.read-more {
  display: inline-block;
  font-size: 14px;
  font-weight: 600;
  color: var(--color-accent);
  margin-top: 8px;
}

.read-more::after {
  content: "→";
  margin-left: 4px;
  transition: margin-left var(--transition-base);
}

.read-more:hover::after {
  margin-left: 8px;
}

/* ==========================================================
   Components —— 卡片、列表、标签、图容器等通用模块
   ========================================================== */

/* ---------- 频道标签 ---------- */
.channel-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.channel-tags li a {
  display: inline-block;
  padding: 8px 18px;
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

.channel-tags li a:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
  background-color: var(--color-accent-soft);
}

/* ---------- 新闻列表 ---------- */
.news-list {
  display: flex;
  flex-direction: column;
}

.news-item {
  padding: 14px 0;
  border-bottom: 1px solid var(--color-border);
}

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

.news-item a {
  display: block;
}

.news-title {
  font-size: 15px;
  font-weight: 500;
  color: var(--color-text);
  line-height: 1.5;
  transition: color var(--transition-base);
}

.news-item a:hover .news-title {
  color: var(--color-accent);
}

.news-date {
  display: block;
  font-size: 13px;
  color: var(--color-text-muted);
  margin-top: 4px;
}

/* ---------- 专题卡片（首页与专题页共用基础） ---------- */
.topic-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.topic-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.topic-card a {
  display: block;
  color: var(--color-text);
}

.topic-card img {
  width: 100%;
  height: 160px;
  object-fit: cover;
}

.topic-card-title {
  font-size: 16px;
  font-weight: 600;
  padding: 14px 16px 6px;
  line-height: 1.4;
}

.topic-card-excerpt {
  font-size: 14px;
  color: var(--color-text-light);
  padding: 0 16px 16px;
  line-height: 1.6;
}

/* ---------- 编辑推荐 ---------- */
.picks-list {
  display: flex;
  flex-direction: column;
}

.pick-item {
  padding: 14px 0;
  border-bottom: 1px solid var(--color-border);
}

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

.pick-item a {
  display: block;
}

.pick-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.5;
}

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

.pick-reason {
  display: block;
  font-size: 13px;
  color: var(--color-text-muted);
  margin-top: 4px;
}

/* ---------- 图片容器通用 ---------- */
.feature-media,
.detail-image,
.channel-figure,
.guide-figure,
.article-figure,
.topic-media {
  overflow: hidden;
  border-radius: var(--radius-md);
  background-color: var(--color-border);
}

.feature-media img,
.detail-image img,
.channel-image,
.figure-img,
.article-figure img,
.topic-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* ---------- 频道索引（侧栏） ---------- */
.channel-index {
  display: flex;
  flex-direction: column;
}

.channel-index li a {
  display: block;
  padding: 10px 14px;
  font-size: 15px;
  color: var(--color-text);
  border-left: 3px solid transparent;
  transition: all var(--transition-base);
}

.channel-index li a:hover {
  color: var(--color-accent);
  background-color: var(--color-accent-soft);
  border-left-color: var(--color-accent);
}

/* ---------- 延伸阅读 / 相关列表 ---------- */
.related-list,
.related-links,
.sidebar-links {
  display: flex;
  flex-direction: column;
}

.related-list li,
.related-links li,
.sidebar-links li {
  padding: 10px 0;
  border-bottom: 1px solid var(--color-border);
}

.related-list li:last-child,
.related-links li:last-child,
.sidebar-links li:last-child {
  border-bottom: none;
}

.related-list a,
.related-links a,
.sidebar-links a {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.5;
  display: block;
}

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

/* ==========================================================
   Pages —— 首页
   ========================================================== */

/* ---------- Hero 区 ---------- */
.hero-section {
  margin-bottom: 40px;
}

.hero-layout {
  display: grid;
  grid-template-columns: 1fr 1.6fr;
  gap: 32px;
  align-items: start;
}

.hero-catalog {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-sm);
}

.hero-catalog .section-title {
  margin-bottom: 12px;
}

.section-intro {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.6;
  margin-bottom: 20px;
}

.hero-feature {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-sm);
}

.feature-media {
  height: 280px;
  margin-bottom: 20px;
}

.feature-content {
  padding: 0 4px;
}

.feature-title {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 10px;
  line-height: 1.4;
}

.feature-excerpt {
  font-size: 15px;
  color: var(--color-text-light);
  line-height: 1.7;
}

/* ---------- 首页三栏栅格 ---------- */
.home-grid {
  display: grid;
  grid-template-columns: 1fr 1.8fr 1fr;
  gap: 28px;
  align-items: start;
  margin-bottom: 40px;
}

.home-sidebar {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

.home-center {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

/* 焦点报道详情 */
.feature-detail {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-sm);
}

.detail-paragraph {
  font-size: 15px;
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: 16px;
}

.detail-paragraph strong {
  color: var(--color-text);
  font-weight: 600;
}

.detail-image {
  height: 240px;
  margin: 20px 0;
}

/* 编辑推荐 */
.editor-picks {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

/* 专题推荐 */
.topic-recommend {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.topic-recommend .topic-card img {
  height: 140px;
}

/* ---------- 来源说明 ---------- */
.source-note {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-orange);
  border-radius: var(--radius-md);
  padding: 24px 28px;
  margin-top: 8px;
}

.source-note .section-title {
  border-left: none;
  padding-left: 0;
  font-size: 18px;
  color: var(--color-orange);
  margin-bottom: 12px;
}

.source-note p {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.7;
  margin-bottom: 8px;
}

.source-note p:last-child {
  margin-bottom: 0;
}

/* ==========================================================
   Pages —— 频道分类页（mfcg/channels.html）
   ========================================================== */

.layout-shell {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 32px;
  align-items: start;
}

.sidebar {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 20px;
}

.sidebar-title {
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--color-border);
}

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

.channel-section {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  margin-bottom: 24px;
  box-shadow: var(--shadow-sm);
}

.channel-section:last-of-type {
  margin-bottom: 28px;
}

.section-desc {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.6;
  margin-bottom: 20px;
}

.preview-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.preview-item {
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 18px;
  transition: all var(--transition-base);
}

.preview-item:hover {
  border-color: var(--color-accent);
  box-shadow: var(--shadow-sm);
}

.preview-title {
  font-size: 15px;
  font-weight: 600;
  margin-bottom: 8px;
  line-height: 1.5;
}

.preview-title a {
  color: var(--color-text);
}

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

.preview-excerpt {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.6;
  margin-bottom: 10px;
}

.preview-item time {
  display: block;
  font-size: 13px;
  color: var(--color-text-muted);
}

.channel-figure {
  height: 260px;
  margin-top: 8px;
}

.channel-figure figcaption {
  font-size: 13px;
  color: var(--color-text-muted);
  padding: 12px 16px;
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border);
}

/* ==========================================================
   Pages —— 内容专题页（mfcg/topics.html）
   ========================================================== */

.topic-listing {
  margin-bottom: 40px;
}

.topic-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.topic-grid .topic-card img {
  height: 180px;
}

.topic-body {
  padding: 16px 20px 20px;
}

.topic-title {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 8px;
  line-height: 1.4;
}

.topic-title a {
  color: var(--color-text);
}

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

.topic-excerpt {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.6;
  margin-bottom: 12px;
}

.topic-link {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-accent);
}

.topic-link::after {
  content: "→";
  margin-left: 4px;
}

/* 专题摘要 */
.topic-summary {
  margin-bottom: 40px;
}

.summary-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.summary-item {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px 24px;
  transition: all var(--transition-base);
}

.summary-item:hover {
  border-color: var(--color-accent);
  box-shadow: var(--shadow-sm);
}

.summary-heading {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--color-text);
}

.summary-item p {
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.6;
  margin-bottom: 10px;
}

.summary-item a {
  font-size: 14px;
  font-weight: 500;
  color: var(--color-accent);
}

/* 相关专题 */
.related-topics {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px 28px;
  margin-top: 8px;
}

.related-heading {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 16px;
}

/* ==========================================================
   Pages —— 实用指南页（mfcg/guide.html）
   ========================================================== */

.content-article {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 36px 40px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 32px;
}

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

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

.guide-section .section-title {
  font-size: 20px;
  margin-bottom: 20px;
}

.lead {
  font-size: 16px;
  font-weight: 500;
  color: var(--color-text);
  line-height: 1.8;
  margin-bottom: 20px;
}

.guide-figure {
  height: 260px;
  margin: 24px 0;
}

.guide-figure figcaption {
  font-size: 13px;
  color: var(--color-text-muted);
  padding: 12px 16px;
  background-color: var(--color-bg);
  border-top: 1px solid var(--color-border);
}

.content-article p {
  font-size: 15px;
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: 16px;
}

.content-article p strong {
  color: var(--color-text);
  font-weight: 600;
}

/* 步骤列表 */
.steps-list {
  margin: 20px 0 24px;
  padding-left: 24px;
  counter-reset: step-counter;
}

.steps-list li {
  position: relative;
  font-size: 15px;
  color: var(--color-text-light);
  line-height: 1.7;
  padding: 10px 0;
  padding-left: 36px;
  counter-increment: step-counter;
}

.steps-list li::before {
  content: counter(step-counter);
  position: absolute;
  left: 0;
  top: 10px;
  width: 26px;
  height: 26px;
  background-color: var(--color-accent-soft);
  color: var(--color-accent);
  font-size: 13px;
  font-weight: 700;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* 延伸阅读（指南页） */
.related-reading {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px 28px;
}

.related-title {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 12px;
}

/* ==========================================================
   Pages —— 深度解读页（mfcg/deep-dive.html）
   ========================================================== */

.content-layout {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 32px;
  align-items: start;
}

.article-body {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 36px 40px;
  box-shadow: var(--shadow-sm);
  min-width: 0;
}

.article-section {
  margin-bottom: 36px;
}

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

.article-section h2 {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 16px;
  padding-left: 12px;
  border-left: 4px solid var(--color-accent);
  line-height: 1.4;
}

.article-section h3 {
  font-size: 17px;
  font-weight: 600;
  margin: 24px 0 10px;
  color: var(--color-text);
}

.article-section p {
  font-size: 15px;
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: 14px;
}

.article-section p strong {
  color: var(--color-text);
  font-weight: 600;
}

.article-figure {
  height: 280px;
  margin: 20px 0;
}

.article-figure figcaption {
  font-size: 13px;
  color: var(--color-text-muted);
  padding: 12px 16px;
  background-color: var(--color-bg);
  border-top: 1px solid var(--color-border);
}

/* 文章内延伸阅读 */
.article-body .related-reading {
  margin-top: 40px;
  border: 1px solid var(--color-border);
  background-color: var(--color-bg);
}

/* 右侧推荐栏 */
.sidebar-right {
  display: flex;
  flex-direction: column;
  gap: 24px;
  position: sticky;
  top: 20px;
}

.sidebar-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

.sidebar-card h2 {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 14px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--color-border);
}

/* ==========================================================
   Pages —— 404 页
   ========================================================== */

.error-main {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 60vh;
}

.error-content {
  text-align: center;
  max-width: 560px;
  padding: 48px 32px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}

.error-code {
  font-size: 72px;
  font-weight: 800;
  color: var(--color-accent);
  line-height: 1;
  margin-bottom: 12px;
}

.error-content h1 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 12px;
}

.error-desc {
  font-size: 15px;
  color: var(--color-text-light);
  line-height: 1.7;
  margin-bottom: 24px;
}

.error-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
  margin-bottom: 20px;
}

.btn-back,
.btn-link {
  display: inline-block;
  padding: 10px 24px;
  font-size: 14px;
  font-weight: 600;
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

.btn-back {
  background-color: var(--color-accent);
  color: var(--color-surface);
}

.btn-back:hover {
  background-color: var(--color-accent-dark);
  color: var(--color-surface);
}

.btn-link {
  background-color: var(--color-surface);
  color: var(--color-accent);
  border: 1px solid var(--color-accent);
}

.btn-link:hover {
  background-color: var(--color-accent-soft);
}

.error-tip {
  font-size: 14px;
  color: var(--color-text-muted);
}

.error-tip a {
  color: var(--color-accent);
  font-weight: 500;
}

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

/* ---------- 平板（≤1024px） ---------- */
@media (max-width: 1024px) {
  .home-grid {
    grid-template-columns: 1fr 1.6fr;
  }

  .home-sidebar.sidebar-right {
    grid-column: 1 / -1;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
  }

  .sidebar-right .topic-recommend {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
  }

  .content-layout {
    grid-template-columns: 1fr;
  }

  .sidebar-right {
    position: static;
    flex-direction: row;
    flex-wrap: wrap;
  }

  .sidebar-card {
    flex: 1;
    min-width: 240px;
  }

  .footer-columns {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }
}

/* ---------- 手机（≤768px） ---------- */
@media (max-width: 768px) {
  .site-main {
    padding: 20px 16px 40px;
  }

  /* 汉堡菜单 */
  .nav-toggle {
    display: flex;
    align-items: center;
    gap: 8px;
    background: none;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: 8px 14px;
    cursor: pointer;
    font-size: 14px;
    color: var(--color-text);
  }

  .nav-toggle-icon {
    display: block;
    width: 18px;
    height: 2px;
    background-color: var(--color-text);
    position: relative;
  }

  .nav-toggle-icon::before,
  .nav-toggle-icon::after {
    content: "";
    position: absolute;
    left: 0;
    width: 18px;
    height: 2px;
    background-color: var(--color-text);
  }

  .nav-toggle-icon::before {
    top: -6px;
  }

  .nav-toggle-icon::after {
    top: 6px;
  }

  .nav-toggle-text {
    font-size: 14px;
    font-weight: 500;
  }

  .header-bottom .site-nav {
    padding: 0 16px;
  }

  .nav-list {
    display: none;
    flex-direction: column;
    padding: 8px 0;
  }

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

  .nav-list li a {
    padding: 12px 16px;
    border-bottom: 1px solid var(--color-border);
  }

  .nav-list li a.is-current {
    border-bottom-color: var(--color-border);
    background-color: var(--color-accent-soft);
  }

  /* 页头 */
  .header-top {
    padding: 12px 16px;
  }

  .brand-slogan {
    display: none;
  }

  .brand-name {
    font-size: 20px;
  }

  .quick-nav.site-nav a {
    padding: 6px 10px;
    font-size: 13px;
  }

  /* Hero */
  .hero-layout {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .hero-catalog,
  .hero-feature {
    padding: 20px;
  }

  .feature-media {
    height: 200px;
  }

  /* 首页三栏 → 单列，核心内容在前 */
  .home-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .home-sidebar.sidebar-left {
    order: 3;
  }

  .home-center {
    order: 1;
  }

  .home-sidebar.sidebar-right {
    order: 2;
    grid-column: auto;
    display: block;
  }

  .sidebar-right .topic-recommend {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .feature-detail,
  .editor-picks,
  .home-sidebar {
    padding: 20px;
  }

  .detail-image {
    height: 180px;
  }

  /* 频道分类页 */
  .layout-shell {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .sidebar {
    position: static;
    padding: 20px;
  }

  .channel-index {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
  }

  .channel-index li a {
    padding: 8px 14px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    border-left: 1px solid var(--color-border);
  }

  .channel-index li a:hover {
    border-left-color: var(--color-accent);
  }

  .channel-section {
    padding: 20px;
  }

  .preview-list {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .channel-figure {
    height: 200px;
  }

  /* 专题页 */
  .topic-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .summary-list {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  /* 指南页 */
  .content-article {
    padding: 24px 20px;
  }

  .guide-figure {
    height: 200px;
  }

  /* 深度解读 */
  .article-body {
    padding: 24px 20px;
  }

  .article-figure {
    height: 200px;
  }

  .content-layout {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .sidebar-right {
    position: static;
    flex-direction: column;
  }

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

  /* 页脚 */
  .footer-columns {
    grid-template-columns: 1fr;
    gap: 28px;
    padding: 36px 20px 20px;
  }

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

  /* 面包屑 */
  .breadcrumb {
    margin-bottom: 18px;
    font-size: 13px;
  }

  /* 页面标题 */
  .page-title {
    font-size: 24px;
  }

  .page-description {
    font-size: 15px;
  }

  .section-title {
    font-size: 19px;
  }

  /* 404 */
  .error-content {
    padding: 32px 20px;
  }

  .error-code {
    font-size: 56px;
  }

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

  .btn-back,
  .btn-link {
    text-align: center;
  }
}

/* ---------- 小屏手机（≤390px） ---------- */
@media (max-width: 390px) {
  .brand-name {
    font-size: 18px;
  }

  .quick-nav.site-nav a {
    padding: 5px 8px;
    font-size: 12px;
  }

  .hero-catalog,
  .hero-feature,
  .feature-detail,
  .editor-picks,
  .home-sidebar {
    padding: 16px;
  }

  .channel-tags li a {
    padding: 6px 14px;
    font-size: 13px;
  }

  .topic-card img {
    height: 140px;
  }

  .preview-item {
    padding: 14px;
  }

  .content-article,
  .article-body {
    padding: 20px 16px;
  }

  .article-section h2 {
    font-size: 19px;
  }

  .steps-list li {
    padding-left: 32px;
  }
}