:root {
    --primary-color: #2C3E50;
    --secondary-color: #3498DB;
    --bg-color: #F5F7FA;
    --card-bg: #FFFFFF;
    --text-primary: #333333;
    --text-secondary: #666666;
    --text-light: #999999;
    --border-color: #E8E8E8;
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.12);
    --shadow-lg: 0 8px 24px rgba(0,0,0,0.15);
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 20px;
    --transition: all 0.3s ease;
    --transition-fast: all 0.15s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
    color: var(--text-primary);
    background-color: var(--bg-color);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

::-webkit-scrollbar-track {
    background: #f1f1f1;
    border-radius: 5px;
}

::-webkit-scrollbar-thumb {
    background: linear-gradient(180deg, #3498DB, #2C3E50);
    border-radius: 5px;
}

::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(180deg, #2980B9, #1a252f);
}

* {
    scrollbar-width: thin;
    scrollbar-color: #3498DB #f1f1f1;
}

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

a:hover {
    color: #2980B9;
}

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

.site-header {
    background: var(--card-bg);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: var(--transition);
}

.site-header.scrolled {
    box-shadow: var(--shadow-md);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 15px 0;
    max-width: 1200px;
    margin: 0 auto;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 24px;
    font-weight: bold;
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

.logo:hover {
    color: var(--primary-color);
    transform: scale(1.02);
}

.logo i {
    font-size: 28px;
    color: var(--secondary-color);
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

.main-nav .nav-list {
    display: flex;
    list-style: none;
    gap: 32px;
    margin: 0;
    padding: 0;
}

.main-nav a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    font-size: 15px;
    transition: var(--transition);
    position: relative;
    padding: 8px 0;
}

.main-nav a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--secondary-color);
    transition: var(--transition);
}

.main-nav a:hover,
.main-nav a.active {
    color: var(--secondary-color);
}

.main-nav a:hover::after,
.main-nav a.active::after {
    width: 100%;
}

.search-box {
    position: relative;
    display: flex;
    align-items: center;
}

.search-box form {
    display: flex;
    align-items: center;
    background: var(--bg-color);
    border-radius: var(--radius-xl);
    overflow: hidden;
    transition: var(--transition);
    border: 2px solid transparent;
}

.search-box form:focus-within {
    border-color: var(--secondary-color);
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.search-box input {
    border: none;
    outline: none;
    padding: 10px 20px;
    background: transparent;
    font-size: 14px;
    width: 220px;
    color: var(--text-primary);
}

.search-box input::placeholder {
    color: var(--text-light);
}

.search-box button {
    border: none;
    background: var(--secondary-color);
    color: white;
    padding: 10px 18px;
    cursor: pointer;
    transition: var(--transition);
    font-size: 14px;
}

.search-box button:hover {
    background: #2980B9;
}

.mobile-menu-toggle {
    display: none;
    cursor: pointer;
    font-size: 24px;
    color: var(--primary-color);
    padding: 8px;
    transition: var(--transition);
}

.mobile-menu-toggle:hover {
    color: var(--secondary-color);
}

.mobile-nav {
    background: var(--card-bg);
    border-top: 1px solid var(--border-color);
    box-shadow: var(--shadow-md);
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
}

.mobile-nav.active {
    max-height: 400px;
}

.mobile-nav ul {
    list-style: none;
    padding: 10px 20px;
    margin: 0;
}

.mobile-nav li {
    border-bottom: 1px solid var(--border-color);
}

.mobile-nav li:last-child {
    border-bottom: none;
}

.mobile-nav a {
    display: block;
    padding: 14px 0;
    color: var(--text-secondary);
    font-size: 15px;
    font-weight: 500;
    transition: var(--transition);
}

.mobile-nav a:hover {
    color: var(--secondary-color);
    padding-left: 10px;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.main-content {
    min-height: calc(100vh - 200px);
    padding: 30px 0;
}

.site-footer {
    background: linear-gradient(135deg, var(--primary-color), #1a252f);
    color: #fff;
    text-align: center;
    padding: 40px 0;
    margin-top: 60px;
}

.site-footer p {
    margin: 8px 0;
    opacity: 0.85;
    font-size: 14px;
}

.site-footer p:first-child {
    font-size: 16px;
    font-weight: 500;
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 16px 0;
    margin-bottom: 24px;
    font-size: 14px;
    color: var(--text-light);
    background: var(--card-bg);
    padding: 16px 20px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
}

.breadcrumb a {
    color: var(--secondary-color);
    transition: var(--transition-fast);
}

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

.breadcrumb i {
    font-size: 12px;
    color: var(--border-color);
}

.tag-list {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 12px;
}

.tag-item {
    display: inline-block;
    background: rgba(52, 152, 219, 0.08);
    color: var(--secondary-color);
    padding: 4px 12px;
    border-radius: var(--radius-xl);
    font-size: 13px;
    font-weight: 500;
    transition: var(--transition-fast);
    border: 1px solid transparent;
}

.tag-item:hover {
    background: rgba(52, 152, 219, 0.15);
    border-color: var(--secondary-color);
    transform: translateY(-1px);
}

.article-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 20px;
    padding: 16px 0;
    margin-bottom: 24px;
    font-size: 14px;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border-color);
}

.article-meta span {
    display: flex;
    align-items: center;
    gap: 6px;
}

.article-meta i {
    color: var(--secondary-color);
}

.reading-progress {
    position: fixed;
    top: 0;
    left: 0;
    width: 0%;
    height: 3px;
    background: linear-gradient(90deg, var(--secondary-color), #2ecc71);
    z-index: 1001;
    transition: width 0.1s ease-out;
    box-shadow: 0 0 10px rgba(52, 152, 219, 0.5);
}

.toc-sidebar {
    position: sticky;
    top: 100px;
    background: var(--card-bg);
    border-radius: var(--radius-md);
    padding: 24px;
    box-shadow: var(--shadow-sm);
    max-height: calc(100vh - 140px);
    overflow-y: auto;
}

.toc-title {
    font-size: 16px;
    font-weight: bold;
    color: var(--primary-color);
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--secondary-color);
}

.toc-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.toc-item {
    margin: 8px 0;
}

.toc-link {
    display: block;
    padding: 6px 12px;
    color: var(--text-secondary);
    font-size: 14px;
    border-left: 3px solid transparent;
    transition: var(--transition-fast);
    line-height: 1.5;
}

.toc-link:hover,
.toc-link.active {
    color: var(--secondary-color);
    border-left-color: var(--secondary-color);
    background: rgba(52, 152, 219, 0.05);
}

.toc-link.level-2 {
    padding-left: 20px;
    font-size: 13px;
}

.toc-link.level-3 {
    padding-left: 32px;
    font-size: 12px;
}

.nav-prev-next {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-top: 40px;
}

.nav-article {
    background: var(--card-bg);
    padding: 20px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    gap: 8px;
}

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

.nav-label {
    font-size: 13px;
    color: var(--text-light);
    font-weight: 500;
}

.nav-article-title {
    font-size: 15px;
    color: var(--text-primary);
    font-weight: 600;
    line-height: 1.4;
}

.nav-article:hover .nav-article-title {
    color: var(--secondary-color);
}

.related-articles {
    margin-top: 50px;
}

.section-title {
    font-size: 22px;
    font-weight: bold;
    color: var(--primary-color);
    margin-bottom: 24px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--border-color);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 60px;
    height: 2px;
    background: var(--secondary-color);
}

.related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 20px;
}

.related-card {
    background: var(--card-bg);
    border-radius: var(--radius-md);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.related-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.related-image {
    height: 140px;
    overflow: hidden;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.related-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s;
}

.related-card:hover .related-image img {
    transform: scale(1.08);
}

.related-content {
    padding: 16px;
}

.related-title {
    font-size: 15px;
    font-weight: 600;
    line-height: 1.4;
    margin-bottom: 8px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

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

.related-title a:hover {
    color: var(--secondary-color);
}

.related-date {
    font-size: 13px;
    color: var(--text-light);
}

.social-share {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-top: 30px;
    padding: 20px 0;
    border-top: 1px solid var(--border-color);
}

.share-label {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

.share-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--bg-color);
    color: var(--text-secondary);
    font-size: 16px;
    transition: var(--transition);
    border: none;
    cursor: pointer;
}

.share-btn:hover {
    background: var(--secondary-color);
    color: white;
    transform: translateY(-2px);
}

.loading-spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255,255,255,.3);
    border-radius: 50%;
    border-top-color: #fff;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.fade-in {
    animation: fadeIn 0.5s ease-in;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.slide-up {
    animation: slideUp 0.4s ease-out;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(30px); }
    to { opacity: 1; transform: translateY(0); }
}