/* ===== CSS 变量 & 主题 ===== */
:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-card: #ffffff;
  --text-primary: #1a1a2e;
  --text-secondary: #6c757d;
  --text-muted: #adb5bd;
  --border-color: #e9ecef;
  --accent: #4f46e5;
  --accent-light: #818cf8;
  --accent-bg: #eef2ff;
  --tag-bg: #f1f3f5;
  --tag-text: #495057;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.25s ease;
  --max-width: 860px;
}

[data-theme="dark"] {
  --bg-primary: #0f0f1a;
  --bg-secondary: #1a1a2e;
  --bg-card: #16213e;
  --text-primary: #e4e6eb;
  --text-secondary: #b0b3b8;
  --text-muted: #6c757d;
  --border-color: #2d2d44;
  --accent: #818cf8;
  --accent-light: #a5b4fc;
  --accent-bg: #1e1b4b;
  --tag-bg: #2d2d44;
  --tag-text: #b0b3b8;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.5);
}

/* ===== 基础重置 ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.75;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background var(--transition), color var(--transition);
}

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

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

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

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ===== 导航栏 ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.85);
  transition: background var(--transition), border-color var(--transition);
}

[data-theme="dark"] .site-header {
  background: rgba(15, 15, 26, 0.85);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.site-logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.5px;
}

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

.site-nav {
  display: flex;
  gap: 0.25rem;
}

.nav-link {
  padding: 0.4rem 1rem;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.925rem;
  font-weight: 500;
  transition: all var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--accent);
  background: var(--accent-bg);
}

.theme-toggle {
  background: none;
  border: 1px solid var(--border-color);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  cursor: pointer;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
}

.theme-toggle:hover {
  border-color: var(--accent);
  background: var(--accent-bg);
}

/* 移动端菜单按钮 */
.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.mobile-menu-btn span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition);
}

/* ===== 主内容区 ===== */
#app {
  flex: 1;
}

.page {
  display: none;
}

.page.active {
  display: block;
  animation: fadeIn 0.35s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ===== 首页 Hero ===== */
.hero {
  background: linear-gradient(135deg, var(--accent-bg), var(--bg-secondary));
  padding: 5rem 0 3.5rem;
  text-align: center;
  border-bottom: 1px solid var(--border-color);
}

.hero-title {
  font-family: 'Noto Serif SC', serif;
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
  letter-spacing: -1px;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

.hero-tags {
  display: flex;
  justify-content: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.tag {
  display: inline-block;
  padding: 0.3rem 0.9rem;
  background: var(--tag-bg);
  color: var(--tag-text);
  border-radius: 20px;
  font-size: 0.875rem;
  font-weight: 500;
}

/* ===== 章节标题 ===== */
.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin: 3rem 0 1.5rem;
  color: var(--text-primary);
}

.page-title {
  font-size: 2rem;
  font-weight: 700;
  margin: 2rem 0 1.5rem;
  color: var(--text-primary);
}

/* ===== 文章卡片（首页网格） ===== */
.post-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
}

.post-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 1.5rem;
  cursor: pointer;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.post-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-light);
}

.post-card-date {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
}

.post-card-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.5;
}

.post-card-summary {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.65;
  flex: 1;
}

.post-card-tags {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
}

.post-card-tag {
  font-size: 0.75rem;
  padding: 0.2rem 0.6rem;
  background: var(--accent-bg);
  color: var(--accent);
  border-radius: 12px;
  font-weight: 500;
}

/* ===== 文章列表页 ===== */
.search-bar {
  position: relative;
  margin-bottom: 1.5rem;
}

.search-bar input {
  width: 100%;
  padding: 0.85rem 1rem 0.85rem 2.75rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius);
  font-size: 1rem;
  background: var(--bg-card);
  color: var(--text-primary);
  font-family: inherit;
  transition: border-color var(--transition);
  outline: none;
}

.search-bar input:focus {
  border-color: var(--accent);
}

.search-icon {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1rem;
}

/* 标签筛选按钮 */
.tag-filter {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 1.5rem;
}

.tag-btn {
  padding: 0.4rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: 20px;
  background: var(--bg-card);
  color: var(--text-secondary);
  font-size: 0.85rem;
  font-family: inherit;
  cursor: pointer;
  transition: all var(--transition);
  font-weight: 500;
}

.tag-btn:hover {
  border-color: var(--accent-light);
  color: var(--accent);
}

.tag-btn.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

/* 列表项 */
.post-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.post-list-item {
  display: flex;
  align-items: flex-start;
  gap: 1.5rem;
  padding: 1.25rem 1.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all var(--transition);
}

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

.post-list-date {
  font-size: 0.85rem;
  color: var(--text-muted);
  white-space: nowrap;
  padding-top: 0.15rem;
  min-width: 90px;
  text-align: right;
}

.post-list-content {
  flex: 1;
  min-width: 0;
}

.post-list-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.3rem;
}

.post-list-summary {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.post-list-tags {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
}

/* ===== 文章详情 ===== */
.post-article {
  max-width: 720px;
  margin: 0 auto;
  padding: 2rem 0;
}

.post-article-header {
  margin-bottom: 2rem;
  text-align: center;
}

.post-article-title {
  font-family: 'Noto Serif SC', serif;
  font-size: 2.25rem;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 0.75rem;
  color: var(--text-primary);
}

.post-article-meta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.post-article-tags {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.post-article-body {
  font-family: 'Noto Serif SC', 'Noto Sans SC', serif;
  font-size: 1.1rem;
  line-height: 2;
  color: var(--text-primary);
}

.post-article-body h2 {
  font-size: 1.5rem;
  margin: 2rem 0 1rem;
  color: var(--text-primary);
}

.post-article-body h3 {
  font-size: 1.25rem;
  margin: 1.5rem 0 0.75rem;
}

.post-article-body p {
  margin-bottom: 1.25rem;
}

.post-article-body ul,
.post-article-body ol {
  margin: 0 0 1.25rem 1.5rem;
}

.post-article-body li {
  margin-bottom: 0.35rem;
}

.post-article-body code {
  background: var(--tag-bg);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.9em;
  font-family: 'SF Mono', 'Fira Code', monospace;
}

.post-article-body pre {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 1.25rem;
  overflow-x: auto;
  margin-bottom: 1.5rem;
  font-size: 0.9rem;
}

.post-article-body pre code {
  background: none;
  padding: 0;
}

.post-article-body blockquote {
  border-left: 3px solid var(--accent);
  padding: 0.75rem 1.25rem;
  margin: 0 0 1.5rem 0;
  background: var(--accent-bg);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--text-secondary);
  font-style: italic;
}

.post-back {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-bottom: 1.5rem;
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  background: none;
  border: none;
  font-family: inherit;
  padding: 0.3rem 0;
  transition: color var(--transition);
}

.post-back:hover {
  color: var(--accent);
}

/* ===== 关于页面 ===== */
.about-content {
  max-width: 640px;
  margin: 3rem auto;
  text-align: center;
  padding: 3rem 2rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
}

.about-avatar {
  font-size: 4rem;
  margin-bottom: 1rem;
}

.about-content h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.about-intro {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.about-content p {
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
}

.about-list {
  list-style: none;
  text-align: left;
  display: inline-block;
  margin: 1rem 0 2rem;
}

.about-list li {
  padding: 0.4rem 0;
  color: var(--text-primary);
  font-size: 1rem;
}

.about-links {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
}

.social-link {
  padding: 0.5rem 1.25rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-weight: 500;
  transition: all var(--transition);
}

.social-link:hover {
  border-color: var(--accent);
  background: var(--accent-bg);
  color: var(--accent);
}

/* ===== 通用按钮 ===== */
.btn {
  display: inline-block;
  padding: 0.6rem 1.5rem;
  border-radius: var(--radius-sm);
  font-weight: 500;
  font-family: inherit;
  font-size: 0.95rem;
  cursor: pointer;
  transition: all var(--transition);
  border: none;
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--border-color);
  color: var(--text-primary);
}

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

.view-all {
  text-align: center;
  margin: 2.5rem 0 3rem;
}

/* ===== 页脚 ===== */
.site-footer {
  border-top: 1px solid var(--border-color);
  padding: 1.5rem 0;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* ===== 回到顶部按钮 ===== */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border-color);
  background: var(--bg-card);
  color: var(--text-secondary);
  font-size: 1.2rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition);
  box-shadow: var(--shadow-sm);
  z-index: 50;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

/* ===== 空状态 ===== */
.empty-state {
  text-align: center;
  padding: 4rem 2rem;
  color: var(--text-muted);
}

.empty-state-icon {
  font-size: 3rem;
  margin-bottom: 0.75rem;
}

.empty-state p {
  font-size: 1.05rem;
}

/* ===== 响应式布局 ===== */
@media (max-width: 768px) {
  .hero {
    padding: 3rem 0 2rem;
  }

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

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

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

  .site-nav {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    flex-direction: column;
    padding: 0.5rem;
    display: none;
  }

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

  .mobile-menu-btn {
    display: flex;
  }

  .post-list-item {
    flex-direction: column;
    gap: 0.3rem;
  }

  .post-list-date {
    text-align: left;
  }

  .post-article-title {
    font-size: 1.6rem;
  }

  .post-article-body {
    font-size: 1rem;
  }

  .about-content {
    padding: 2rem 1.25rem;
    margin: 1.5rem auto;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 1rem;
  }

  .hero {
    padding: 2.5rem 0 1.5rem;
  }

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