/* ========================================
   THBEV - 泰国饮料股票资讯网站样式表
   响应式设计 | 现代化风格
======================================== */

/* CSS变量定义 */
:root {
    --primary-color: #1a73e8;
    --primary-dark: #1557b0;
    --secondary-color: #ff6b35;
    --text-color: #333333;
    --text-light: #666666;
    --text-muted: #999999;
    --bg-color: #ffffff;
    --bg-light: #f8f9fa;
    --bg-dark: #1a1a2e;
    --border-color: #e0e0e0;
    --shadow: 0 2px 10px rgba(0,0,0,0.1);
    --shadow-hover: 0 5px 20px rgba(0,0,0,0.15);
    --transition: all 0.3s ease;
    --container-width: 1200px;
    --header-height: 70px;
}

/* 重置样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', 'Microsoft YaHei', -apple-system, BlinkMacSystemFont, sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

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

ul {
    list-style: none;
}

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

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

/* ========================================
   头部导航
======================================== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--bg-color);
    box-shadow: var(--shadow);
    z-index: 1000;
    transition: var(--transition);
}

.header.scrolled {
    box-shadow: 0 2px 20px rgba(0,0,0,0.1);
}

.header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}

.logo {
    display: flex;
    align-items: center;
    font-size: 24px;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    flex-shrink: 0;
}

.logo i {
    margin-right: 10px;
    font-size: 28px;
}

.logo img {
    width: 40px;
    height: 40px;
    margin-right: 10px;
    object-fit: contain;
    flex-shrink: 0;
}

.logo span {
    font-size: 24px;
    font-weight: 700;
    color: var(--primary-color);
    white-space: nowrap;
    line-height: 1;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: 25px;
    flex: 1;
    justify-content: center;
    margin: 0 20px;
}

.nav-menu > a,
.nav-menu > .nav-item > a {
    font-weight: 500;
    color: var(--text-color);
    position: relative;
    padding: 5px 0;
    font-size: 15px;
    white-space: nowrap;
}

.nav-menu > a::after,
.nav-menu > .nav-item > a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: var(--transition);
}

.nav-menu > a:hover,
.nav-menu > .nav-item > a:hover,
.nav-menu > a.active,
.nav-menu > .nav-item > a.active {
    color: var(--primary-color);
}

.nav-menu > a:hover::after,
.nav-menu > .nav-item > a:hover::after,
.nav-menu > a.active::after,
.nav-menu > .nav-item > a.active::after {
    width: 100%;
}

/* 导航下拉菜单 */
/* 导航下拉菜单 */
.nav-item {
    position: relative;
    height: 100%;
    display: flex;
    align-items: center;
}

.nav-item > a {
    display: flex;
    align-items: center;
    height: 100%;
}

.nav-dropdown {
    position: absolute;
    top: 100%;
    left: 0;
    min-width: 160px;
    background: var(--bg-color);
    box-shadow: var(--shadow-hover);
    border-radius: 8px;
    padding: 8px 0;
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: var(--transition);
    z-index: 1001;
    display: flex;
    flex-direction: column;
}

.nav-item:hover .nav-dropdown {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.nav-dropdown a {
    display: block;
    padding: 10px 20px;
    font-size: 14px;
    color: var(--text-color);
    white-space: nowrap;
}

.nav-dropdown a:hover {
    background: var(--bg-light);
    color: var(--primary-color);
}

.nav-dropdown a.active {
    color: var(--primary-color);
    background: var(--bg-light);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 15px;
}

.search-btn,
.menu-toggle {
    width: 40px;
    height: 40px;
    border: none;
    background: transparent;
    cursor: pointer;
    font-size: 20px;
    color: var(--text-color);
    border-radius: 50%;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.search-btn:hover,
.menu-toggle:hover {
    background: var(--bg-light);
    color: var(--primary-color);
}

.menu-toggle {
    display: none;
}

/* ========================================
   语言选择器
======================================== */
.language-selector {
    position: relative;
}

.language-btn {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 8px 12px;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: 20px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-color);
    transition: var(--transition);
}

.language-btn:hover {
    background: var(--bg-light);
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.language-btn i {
    font-size: 16px;
}

.language-dropdown {
    position: absolute;
    top: 100%;
    right: 0;
    margin-top: 10px;
    background: var(--bg-color);
    border-radius: 10px;
    box-shadow: var(--shadow-hover);
    min-width: 150px;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: var(--transition);
    z-index: 1001;
    overflow: hidden;
}

.language-dropdown.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.language-dropdown a {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 15px;
    font-size: 14px;
    transition: var(--transition);
}

.language-dropdown a:hover {
    background: var(--bg-light);
    color: var(--primary-color);
}

.language-dropdown a.active {
    background: var(--primary-color);
    color: white;
}

/* ========================================
   搜索框
======================================== */
.search-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,0.9);
    z-index: 2000;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
}

.search-overlay.active {
    opacity: 1;
    visibility: visible;
}

.search-box {
    width: 90%;
    max-width: 600px;
    position: relative;
}

.search-box input {
    width: 100%;
    padding: 20px 60px 20px 25px;
    font-size: 18px;
    border: none;
    border-radius: 50px;
    background: var(--bg-color);
    outline: none;
}

.search-box button {
    position: absolute;
    right: 5px;
    top: 50%;
    transform: translateY(-50%);
    width: 50px;
    height: 50px;
    border: none;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    cursor: pointer;
    font-size: 18px;
    transition: var(--transition);
}

.search-box button:hover {
    background: var(--primary-dark);
}

.search-close {
    position: absolute;
    top: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    border: none;
    background: transparent;
    color: white;
    font-size: 30px;
    cursor: pointer;
    transition: var(--transition);
}

.search-close:hover {
    transform: rotate(90deg);
}

/* ========================================
   主要内容区域
======================================== */
.main-content {
    margin-top: var(--header-height);
    min-height: calc(100vh - var(--header-height) - 400px);
}

/* ========================================
   轮播图/英雄区
======================================== */
.hero-section {
    position: relative;
    height: 600px;
    overflow: hidden;
    background: linear-gradient(135deg, #1a9aa8 0%, #0d7a8a 50%, #0a5a6a 100%);
}

.hero-slider {
    position: relative;
    height: 100%;
}

.hero-slide {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0;
    visibility: hidden;
    transition: all 0.8s ease;
    z-index: 1;
}

.hero-slide.active {
    opacity: 1;
    visibility: visible;
    z-index: 5;
}

.hero-slide .bg-image {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, #1a9aa8 0%, #0d7a8a 50%, #0a5a6a 100%);
    z-index: 1;
}

.hero-slide .bg-image::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(26, 154, 168, 0.4) 0%, rgba(13, 122, 138, 0.3) 50%, rgba(10, 90, 106, 0.2) 100%);
}

.hero-content {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 10;
    display: flex;
    align-items: center;
}

.hero-text {
    max-width: 600px;
    color: #ffffff;
    padding: 0 20px;
    position: relative;
    z-index: 20;
}

.hero-text h1,
.hero-text p,
.hero-text .meta,
.hero-text .category {
    color: #ffffff;
}

.hero-text .category {
    display: inline-block;
    padding: 8px 20px;
    background: var(--secondary-color);
    color: white;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    border-radius: 30px;
    margin-bottom: 20px;
}

.hero-text h1 {
    font-size: 48px;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 20px;
}

.hero-text p {
    font-size: 18px;
    opacity: 0.9;
    margin-bottom: 30px;
}

.hero-text .meta {
    display: flex;
    align-items: center;
    gap: 20px;
    font-size: 14px;
    opacity: 0.8;
}

.hero-text .meta span {
    display: flex;
    align-items: center;
    gap: 5px;
}

.hero-nav {
    position: absolute;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    gap: 10px;
    z-index: 10;
}

.hero-nav button {
    width: 12px;
    height: 12px;
    border: 2px solid white;
    background: transparent;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
}

.hero-nav button.active,
.hero-nav button:hover {
    background: white;
}

.hero-arrows {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 100%;
    display: flex;
    justify-content: space-between;
    padding: 0 30px;
    z-index: 10;
}

.hero-arrows button {
    width: 50px;
    height: 50px;
    border: 2px solid rgba(255,255,255,0.5);
    background: rgba(0,0,0,0.3);
    color: white;
    border-radius: 50%;
    cursor: pointer;
    font-size: 20px;
    transition: var(--transition);
}

.hero-arrows button:hover {
    background: var(--primary-color);
    border-color: var(--primary-color);
}

/* ========================================
   区块标题
======================================== */
.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 40px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--border-color);
}

.section-title {
    font-size: 28px;
    font-weight: 700;
    color: var(--text-color);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -22px;
    left: 0;
    width: 60px;
    height: 2px;
    background: var(--primary-color);
}

.view-all {
    display: flex;
    align-items: center;
    gap: 5px;
    color: var(--primary-color);
    font-weight: 500;
}

.view-all:hover {
    gap: 10px;
}

/* ========================================
   页面标题区
======================================== */
.about-hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    padding: 60px 0;
    color: white;
    text-align: center;
}

.about-hero h1 {
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 15px;
}

.about-hero p {
    font-size: 16px;
    opacity: 0.9;
}

@media (max-width: 768px) {
    .about-hero {
        padding: 40px 0;
    }
    
    .about-hero h1 {
        font-size: 28px;
    }
    
    .about-hero p {
        font-size: 14px;
    }
}

/* ========================================
   新闻卡片
======================================== */
.news-section {
    padding: 80px 0;
}

@media (max-width: 768px) {
    .news-section {
        padding: 50px 0;
    }
}

.news-section.bg-light {
    background: var(--bg-light);
}

.news-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.news-grid.two-col {
    grid-template-columns: repeat(2, 1fr);
}

.news-grid.four-col {
    grid-template-columns: repeat(4, 1fr);
}

.news-card {
    background: var(--bg-color);
    border-radius: 10px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

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

.news-card .image {
    position: relative;
    height: 200px;
    overflow: hidden;
}

.news-card .image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
}

.news-card:hover .image img {
    transform: scale(1.1);
}

.news-card .category-tag {
    position: absolute;
    top: 15px;
    left: 15px;
    padding: 5px 15px;
    background: var(--primary-color);
    color: white;
    font-size: 12px;
    font-weight: 600;
    border-radius: 20px;
}

.news-card .content {
    padding: 20px;
}

.news-card h3 {
    font-size: 18px;
    font-weight: 600;
    line-height: 1.4;
    margin-bottom: 15px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.news-card h3 a:hover {
    color: var(--primary-color);
}

.news-card .meta {
    display: flex;
    align-items: center;
    gap: 15px;
    font-size: 13px;
    color: var(--text-muted);
}

.news-card .meta span {
    display: flex;
    align-items: center;
    gap: 5px;
}

/* 大卡片样式 */
.news-card.featured {
    grid-column: span 2;
    display: flex;
}

.news-card.featured .image {
    width: 50%;
    height: auto;
}

.news-card.featured .content {
    width: 50%;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.news-card.featured h3 {
    font-size: 24px;
}

.news-card.featured p {
    color: var(--text-light);
    margin-top: 10px;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* 横向卡片 */
.news-card.horizontal {
    display: flex;
    gap: 20px;
}

.news-card.horizontal .image {
    width: 120px;
    height: 120px;
    flex-shrink: 0;
    border-radius: 8px;
}

.news-card.horizontal .content {
    padding: 0;
    flex: 1;
}

.news-card.horizontal h3 {
    font-size: 16px;
}

/* ========================================
   侧边栏
======================================== */
.content-layout {
    display: grid;
    grid-template-columns: 1fr 350px;
    gap: 40px;
}

.sidebar .widget {
    background: var(--bg-color);
    border-radius: 10px;
    padding: 25px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
}

.sidebar .widget-title {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--border-color);
    position: relative;
}

.sidebar .widget-title::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 40px;
    height: 2px;
    background: var(--primary-color);
}

/* 热门新闻 */
.trending-list {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.trending-item {
    display: flex;
    gap: 15px;
    align-items: flex-start;
}

.trending-item .number {
    width: 35px;
    height: 35px;
    background: var(--bg-light);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    color: var(--primary-color);
    flex-shrink: 0;
}

.trending-item:nth-child(1) .number {
    background: var(--secondary-color);
    color: white;
}

.trending-item:nth-child(2) .number {
    background: #ffa726;
    color: white;
}

.trending-item:nth-child(3) .number {
    background: #66bb6a;
    color: white;
}

.trending-item h4 {
    font-size: 15px;
    font-weight: 600;
    line-height: 1.4;
}

.trending-item h4 a:hover {
    color: var(--primary-color);
}

.trending-item .date {
    font-size: 12px;
    color: var(--text-muted);
    margin-top: 5px;
}

/* 分类 */
.category-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.category-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 15px;
    background: var(--bg-light);
    border-radius: 8px;
    transition: var(--transition);
}

.category-item:hover {
    background: var(--primary-color);
    color: white;
}

.category-item span:last-child {
    width: 28px;
    height: 28px;
    background: rgba(255,255,255,0.2);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
}

/* 标签云 */
.tag-cloud {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.tag-cloud a {
    padding: 8px 16px;
    background: var(--bg-light);
    border-radius: 20px;
    font-size: 13px;
    transition: var(--transition);
}

.tag-cloud a:hover {
    background: var(--primary-color);
    color: white;
}

/* ========================================
   分类区块
======================================== */
.category-section {
    padding: 80px 0;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 25px;
}

.category-box {
    position: relative;
    height: 250px;
    border-radius: 15px;
    overflow: hidden;
    cursor: pointer;
}

.category-box img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
}

.category-box:hover img {
    transform: scale(1.1);
}

.category-box .overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to top, rgba(0,0,0,0.8) 0%, rgba(0,0,0,0.3) 50%, rgba(0,0,0,0.1) 100%);
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    padding: 25px;
    color: white;
}

.category-box h3 {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 5px;
}

.category-box span {
    font-size: 14px;
    opacity: 0.8;
}

/* ========================================
   详情页
======================================== */
.detail-section {
    padding: 60px 0;
}

.article-header {
    margin-bottom: 40px;
}

.article-header .category {
    display: inline-block;
    padding: 8px 20px;
    background: var(--primary-color);
    color: white;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    border-radius: 30px;
    margin-bottom: 20px;
}

.article-header h1 {
    font-size: 36px;
    font-weight: 700;
    line-height: 1.3;
    margin-bottom: 25px;
}

.article-header .meta {
    display: flex;
    align-items: center;
    gap: 25px;
    color: var(--text-muted);
    font-size: 14px;
}

.article-header .meta .author {
    display: flex;
    align-items: center;
    gap: 10px;
}

.article-header .meta .author img {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    object-fit: cover;
}

.article-header .meta span {
    display: flex;
    align-items: center;
    gap: 5px;
}

.article-image {
    width: 100%;
    height: 500px;
    object-fit: cover;
    border-radius: 15px;
    margin-bottom: 40px;
}

.article-content {
    font-size: 17px;
    line-height: 1.8;
    color: var(--text-color);
}

.article-content p {
    margin-bottom: 25px;
}

.article-content h2 {
    font-size: 28px;
    font-weight: 700;
    margin: 40px 0 20px;
}

.article-content h3 {
    font-size: 22px;
    font-weight: 600;
    margin: 30px 0 15px;
}

.article-content img {
    width: 100%;
    border-radius: 10px;
    margin: 30px 0;
}

.article-content blockquote {
    border-left: 4px solid var(--primary-color);
    padding: 20px 30px;
    background: var(--bg-light);
    margin: 30px 0;
    font-style: italic;
    color: var(--text-light);
}

.article-content ul,
.article-content ol {
    margin: 20px 0;
    padding-left: 30px;
}

.article-content li {
    margin-bottom: 10px;
}

/* 分享 */
.article-share {
    display: flex;
    align-items: center;
    gap: 15px;
    margin-top: 50px;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
}

.article-share span {
    font-weight: 600;
}

.article-share a {
    width: 40px;
    height: 40px;
    background: var(--bg-light);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.article-share a:hover {
    background: var(--primary-color);
    color: white;
}

/* 相关文章 */
.related-articles {
    margin-top: 60px;
}

/* 上一篇/下一篇导航 */
.article-nav {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 30px;
    margin-top: 50px;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
}

.article-nav-item {
    padding: 20px;
    background: var(--bg-light);
    border-radius: 10px;
    transition: var(--transition);
}

.article-nav-item:hover {
    background: var(--primary-color);
    color: white;
}

.article-nav-item span {
    font-size: 12px;
    opacity: 0.7;
    display: block;
    margin-bottom: 10px;
}

.article-nav-item h4 {
    font-size: 16px;
    font-weight: 600;
}

.article-nav-item.next {
    text-align: right;
}

/* ========================================
   分页
======================================== */
.pagination {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-top: 50px;
}

.pagination a,
.pagination span {
    width: 45px;
    height: 45px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-weight: 500;
    transition: var(--transition);
}

.pagination a:hover,
.pagination a.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* ========================================
   页脚
======================================== */
.footer {
    background: var(--bg-dark);
    color: white;
    padding: 80px 0 0;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 60px;
}

.footer-brand .logo {
    color: white;
    margin-bottom: 20px;
}

.footer-brand p {
    color: rgba(255,255,255,0.7);
    margin-bottom: 25px;
    line-height: 1.8;
}

.footer-brand .social {
    display: flex;
    gap: 15px;
}

.footer-brand .social a {
    width: 40px;
    height: 40px;
    background: rgba(255,255,255,0.1);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.footer-brand .social a:hover {
    background: var(--primary-color);
}

.footer-links h4 {
    font-size: 18px;
    font-weight: 700;
    margin-bottom: 25px;
}

.footer-links ul li {
    margin-bottom: 12px;
}

.footer-links ul li a {
    color: rgba(255,255,255,0.7);
    transition: var(--transition);
}

.footer-links ul li a:hover {
    color: white;
    padding-left: 5px;
}

.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.1);
    padding: 25px 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: rgba(255,255,255,0.6);
    font-size: 14px;
}

.footer-bottom a {
    color: rgba(255,255,255,0.6);
}

.footer-bottom a:hover {
    color: white;
}

/* ========================================
   返回顶部
======================================== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    font-size: 20px;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    z-index: 999;
    display: flex;
    align-items: center;
    justify-content: center;
}

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

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-5px);
}

/* ========================================
   响应式设计
======================================== */
@media (max-width: 1200px) {
    .news-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .news-grid.four-col {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .category-grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .content-layout {
        grid-template-columns: 1fr;
    }
    
    .sidebar {
        order: 2;
    }
}

@media (max-width: 992px) {
    .nav-menu {
        position: fixed;
        top: var(--header-height);
        left: -100%;
        width: 100%;
        height: calc(100vh - var(--header-height));
        background: var(--bg-color);
        flex-direction: column;
        padding: 40px 20px;
        transition: var(--transition);
        gap: 0;
        overflow-y: auto;
    }
    
    .nav-menu.active {
        left: 0;
    }
    
    .nav-item {
        width: 100%;
        border-bottom: 1px solid var(--border-color);
    }
    
    .nav-item > a {
        padding: 15px 0;
        font-size: 18px;
        justify-content: space-between;
    }
    
    .nav-dropdown {
        position: static;
        opacity: 1;
        visibility: visible;
        transform: none;
        box-shadow: none;
        padding: 0 0 10px 20px;
        display: none;
    }
    
    .nav-item.active .nav-dropdown {
        display: block;
    }
    
    .nav-dropdown a {
        padding: 10px 0;
        font-size: 16px;
    }
    
    .menu-toggle {
        display: flex;
    }
    
    .hero-text h1 {
        font-size: 36px;
    }
    
    .news-card.featured {
        grid-column: span 1;
        flex-direction: column;
    }
    
    .news-card.featured .image,
    .news-card.featured .content {
        width: 100%;
    }
    
    .news-card.featured .image {
        height: 250px;
    }
    
    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .news-grid,
    .news-grid.two-col,
    .news-grid.four-col {
        grid-template-columns: 1fr;
    }
    
    .category-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .hero-section {
        height: 500px;
    }
    
    .hero-text h1 {
        font-size: 28px;
    }
    
    .hero-arrows {
        display: none;
    }
    
    .section-title {
        font-size: 24px;
    }
    
    .article-header h1 {
        font-size: 26px;
    }
    
    .article-image {
        height: 300px;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .footer-brand .social {
        justify-content: center;
    }
    
    .footer-bottom {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    
    .article-nav {
        grid-template-columns: 1fr;
    }
    
    .article-nav-item.next {
        text-align: left;
    }
}

@media (max-width: 480px) {
    .category-grid {
        grid-template-columns: 1fr;
    }
    
    .hero-text .category {
        font-size: 10px;
        padding: 6px 15px;
    }
    
    .hero-text h1 {
        font-size: 24px;
    }
    
    .hero-text p {
        font-size: 14px;
    }
}

/* ========================================
   动画效果
======================================== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.fade-in-up {
    animation: fadeInUp 0.6s ease forwards;
}

/* 延迟动画类 */
.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }
.delay-5 { animation-delay: 0.5s; }