/* Reset & Base Styles */
:root {
    --primary-color: #FF3366; /* 活力红 */
    --secondary-color: #33CCFF; /* 科技蓝 */
    --accent-color: #FFCC00; /* 柠檬黄 */
    --bg-color: #f9f9f9;
    --text-color: #333;
    --light-text: #666;
    --white: #fff;
    --shadow: 0 4px 12px rgba(0,0,0,0.1);
    --radius: 12px;
}

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

body {
    font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

a {
    text-decoration: none;
    color: inherit;
    transition: color 0.3s;
}

ul {
    list-style: none;
}

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

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

/* Header */
.site-header {
    background: var(--white);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 15px 0;
}

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

.main-nav ul {
    display: flex;
    gap: 30px;
}

.main-nav a {
    font-weight: 600;
    font-size: 16px;
}

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

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
}

.mobile-menu-toggle span {
    width: 25px;
    height: 3px;
    background: var(--text-color);
}

/* Hero Section */
.hero-section {
    height: 500px;
    background-size: cover;
    background-position: center;
    position: relative;
    display: flex;
    align-items: center;
    color: var(--white);
    text-align: center;
}

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(255,51,102,0.8), rgba(51,204,255,0.8));
}

.hero-content {
    position: relative;
    z-index: 1;
    width: 100%;
}

.brand-title {
    font-size: 48px;
    margin-bottom: 20px;
    font-weight: 800;
}

.highlight {
    color: var(--accent-color);
}

.hero-subtitle {
    font-size: 24px;
    margin-bottom: 30px;
    opacity: 0.9;
}

.hero-tags span {
    display: inline-block;
    background: rgba(255,255,255,0.2);
    padding: 5px 15px;
    border-radius: 20px;
    margin: 0 5px;
    font-size: 14px;
}

.cta-button {
    display: inline-block;
    margin-top: 40px;
    padding: 15px 40px;
    background: var(--white);
    color: var(--primary-color);
    font-weight: bold;
    border-radius: 30px;
    font-size: 18px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
    transition: transform 0.3s;
}

.cta-button:hover {
    transform: translateY(-3px);
}

/* Sections */
.section {
    padding: 80px 0;
}

.section-title {
    text-align: center;
    font-size: 32px;
    margin-bottom: 50px;
    color: var(--text-color);
}

.sub-text {
    display: block;
    font-size: 16px;
    color: var(--light-text);
    margin-top: 10px;
    font-weight: normal;
}

/* Video Grid */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 30px;
}

.video-card {
    background: var(--white);
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: transform 0.3s;
}

.video-card:hover {
    transform: translateY(-5px);
}

.video-thumbnail {
    position: relative;
    height: 180px;
    overflow: hidden;
}

.video-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.5s;
}

.video-card:hover .video-thumbnail img {
    transform: scale(1.05);
}

.play-icon {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 50px;
    height: 50px;
    background: rgba(0,0,0,0.6);
    border-radius: 50%;
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    opacity: 0;
    transition: opacity 0.3s;
}

.video-card:hover .play-icon {
    opacity: 1;
}

.video-duration {
    position: absolute;
    bottom: 10px;
    right: 10px;
    background: rgba(0,0,0,0.8);
    color: #fff;
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 12px;
}

.video-info {
    padding: 20px;
}

.video-title {
    font-size: 16px;
    margin-bottom: 10px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.video-meta {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    color: var(--light-text);
    margin-bottom: 10px;
}

.video-tags span {
    font-size: 12px;
    color: var(--primary-color);
    background: rgba(255,51,102,0.1);
    padding: 2px 8px;
    border-radius: 4px;
    margin-right: 5px;
}

.more-link {
    text-align: center;
    margin-top: 50px;
}

.more-link a {
    color: var(--primary-color);
    font-weight: bold;
    font-size: 18px;
}

/* AI Features */
.ai-features {
    background: #fff;
}

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

.feature-item {
    text-align: center;
    padding: 30px;
    background: var(--bg-color);
    border-radius: var(--radius);
}

.feature-icon {
    font-size: 48px;
    margin-bottom: 20px;
}

.feature-item h3 {
    margin-bottom: 15px;
}

/* Experts */
.expert-list {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 30px;
}

.expert-card {
    background: var(--white);
    padding: 30px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    display: flex;
    gap: 20px;
    align-items: center;
}

.expert-avatar {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    overflow: hidden;
    flex-shrink: 0;
}

.expert-avatar img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.expert-info h3 {
    margin-bottom: 5px;
}

.expert-info .role {
    color: var(--primary-color);
    font-size: 14px;
    margin-bottom: 10px;
}

.expert-info .desc {
    font-size: 14px;
    color: var(--light-text);
    margin-bottom: 15px;
}

.expert-link {
    font-size: 14px;
    color: var(--secondary-color);
    font-weight: bold;
}

/* Footer */
.site-footer {
    background: #222;
    color: #fff;
    padding: 60px 0 20px;
}

.footer-content {
    display: grid;
    grid-template-columns: 1.5fr 1fr 1fr;
    gap: 50px;
    margin-bottom: 40px;
}

.footer-brand img {
    margin-bottom: 20px;
    filter: brightness(0) invert(1);
}

.footer-brand p {
    color: #999;
    margin-bottom: 10px;
    font-size: 14px;
}

.footer-links h4, .footer-social h4 {
    font-size: 18px;
    margin-bottom: 20px;
}

.footer-links ul li {
    margin-bottom: 10px;
}

.footer-links a {
    color: #999;
}

.footer-links a:hover {
    color: #fff;
}

.qr-codes {
    display: flex;
    gap: 20px;
}

.qr-item {
    text-align: center;
}

.qr-placeholder {
    width: 100px;
    height: 100px;
    background: #fff;
    color: #333;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 10px;
    font-size: 12px;
}

.qr-item span {
    font-size: 12px;
    color: #999;
}

.copyright {
    border-top: 1px solid #333;
    padding-top: 20px;
    text-align: center;
    font-size: 14px;
    color: #666;
}

/* Responsive */
@media (max-width: 768px) {
    .main-nav {
        display: none;
    }
    
    .mobile-menu-toggle {
        display: flex;
    }
    
    .hero-section {
        height: 400px;
    }
    
    .brand-title {
        font-size: 32px;
    }
    
    .feature-grid, .expert-list, .footer-content {
        grid-template-columns: 1fr;
    }
    
    .expert-card {
        flex-direction: column;
        text-align: center;
    }
}