:root {
    --color-primary: #00a8ff;
    --color-primary-dark: #0088cc;
    --color-secondary: #ff6b35;
    --color-bg: #0a0a0a;
    --color-bg-light: #141414;
    --color-bg-card: #1a1a1a;
    --color-text: #ffffff;
    --color-text-muted: #888888;
    --color-text-light: #cccccc;
    --color-border: #333333;
    --color-overlay: rgba(0, 0, 0, 0.7);
    
    --font-primary: 'PingFang SC', 'Microsoft YaHei', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-display: 'DIN Alternate', 'Helvetica Neue', Arial, sans-serif;
    
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --spacing-xxl: 48px;
    --spacing-xxxl: 64px;
    
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    --header-height: 72px;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    overflow-x: hidden;
}

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

img {
    max-width: 100%;
    height: auto;
    display: block;
    filter: saturate(0.85) contrast(1.08);
    transition: filter var(--transition-normal), transform var(--transition-slow);
}

img:hover {
    filter: saturate(1) contrast(1.12);
}

.photo-style {
    filter: saturate(0.75) contrast(1.1) brightness(1.02);
    object-fit: cover;
}

.photo-style:hover {
    filter: saturate(0.9) contrast(1.15) brightness(1.05);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: linear-gradient(180deg, rgba(10, 10, 10, 0.95) 0%, rgba(10, 10, 10, 0) 100%);
    z-index: 1000;
    transition: background var(--transition-normal);
}

.header.scrolled {
    background: rgba(10, 10, 10, 0.98);
    backdrop-filter: blur(10px);
}

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

.logo {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.logo-text {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 700;
    letter-spacing: 4px;
    background: linear-gradient(135deg, var(--color-text) 0%, var(--color-primary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo-slogan {
    font-size: 10px;
    letter-spacing: 3px;
    color: var(--color-text-muted);
}

.nav {
    display: flex;
    gap: var(--spacing-xl);
}

.nav-item {
    font-size: 14px;
    font-weight: 500;
    color: var(--color-text-light);
    position: relative;
    padding: var(--spacing-sm) 0;
}

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

.nav-item:hover {
    color: var(--color-text);
}

.nav-item:hover::after {
    width: 100%;
}

.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
}

.hero-video {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.hero-background::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.unsplash.com/photo-1574717024653-61fd2cf4d44d?w=1920') center/cover no-repeat;
    z-index: -1;
}

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(180deg, 
        rgba(10, 10, 10, 0.3) 0%, 
        rgba(10, 10, 10, 0.6) 50%,
        rgba(10, 10, 10, 0.9) 100%);
}

.hero-content {
    text-align: center;
    z-index: 1;
    animation: fadeInUp 1s ease-out;
}

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

.hero-title {
    font-family: var(--font-display);
    font-size: 80px;
    font-weight: 900;
    letter-spacing: 12px;
    margin-bottom: var(--spacing-sm);
    background: linear-gradient(135deg, #ffffff 0%, #00a8ff 50%, #00ff88 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: 0 0 60px rgba(0, 168, 255, 0.5);
}

.hero-subtitle {
    font-family: var(--font-display);
    font-size: 18px;
    letter-spacing: 8px;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xl);
}

.hero-desc {
    font-size: 16px;
    color: var(--color-text-light);
    margin-bottom: var(--spacing-xxl);
    max-width: 500px;
    margin-left: auto;
    margin-right: auto;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 14px 32px;
    font-size: 14px;
    font-weight: 600;
    border-radius: var(--radius-md);
    transition: all var(--transition-normal);
    cursor: pointer;
    border: none;
    outline: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: white;
    box-shadow: 0 4px 20px rgba(0, 168, 255, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 30px rgba(0, 168, 255, 0.5);
}

.btn-secondary {
    background: transparent;
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--color-text);
}

.scroll-indicator {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--color-text-muted);
    font-size: 12px;
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateX(-50%) translateY(0);
    }
    40% {
        transform: translateX(-50%) translateY(-10px);
    }
    60% {
        transform: translateX(-50%) translateY(-5px);
    }
}

.scroll-arrow {
    width: 20px;
    height: 20px;
    border-right: 2px solid var(--color-text-muted);
    border-bottom: 2px solid var(--color-text-muted);
    transform: rotate(45deg);
}

.features {
    padding: var(--spacing-xxxl) 0;
    background: var(--color-bg);
}

.section-title {
    font-size: 32px;
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-xxl);
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 3px;
    background: var(--color-primary);
    margin: var(--spacing-md) auto 0;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-lg);
}

.feature-card {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-5px);
    border-color: var(--color-primary);
    box-shadow: 0 10px 40px rgba(0, 168, 255, 0.15);
}

.feature-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto var(--spacing-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, rgba(0, 168, 255, 0.2) 0%, rgba(0, 255, 136, 0.1) 100%);
    border-radius: var(--radius-md);
}

.feature-icon svg {
    width: 28px;
    height: 28px;
    stroke: var(--color-primary);
}

.feature-title {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.feature-desc {
    font-size: 14px;
    color: var(--color-text-muted);
    line-height: 1.6;
}

.showcase {
    padding: var(--spacing-xxxl) 0;
    background: var(--color-bg-light);
}

.showcase-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(2, 250px);
    gap: var(--spacing-md);
}

.showcase-item {
    position: relative;
    border-radius: var(--radius-lg);
    overflow: hidden;
    cursor: pointer;
}

.showcase-large {
    grid-column: span 2;
    grid-row: span 2;
}

.showcase-cover {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.showcase-cover img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.showcase-item:hover .showcase-cover img {
    transform: scale(1.1);
}

.showcase-item::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(180deg, 
        transparent 40%, 
        rgba(0, 0, 0, 0.8) 100%);
    transition: background var(--transition-normal);
}

.showcase-item:hover::after {
    background: linear-gradient(180deg, 
        transparent 30%, 
        rgba(0, 168, 255, 0.3) 100%);
}

.showcase-info {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: var(--spacing-lg);
    z-index: 1;
}

.showcase-title {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.showcase-count {
    font-size: 13px;
    color: var(--color-text-muted);
}

.stats {
    padding: var(--spacing-xxxl) 0;
    background: var(--color-bg);
    border-top: 1px solid var(--color-border);
    border-bottom: 1px solid var(--color-border);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-xl);
    text-align: center;
}

.stat-item {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.stat-number {
    font-family: var(--font-display);
    font-size: 48px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--color-primary) 0%, #00ff88 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

.cta {
    padding: var(--spacing-xxxl) 0;
    background: linear-gradient(135deg, 
        rgba(0, 168, 255, 0.1) 0%, 
        rgba(0, 255, 136, 0.05) 100%);
}

.cta-content {
    text-align: center;
}

.cta-title {
    font-size: 36px;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

.cta-desc {
    font-size: 16px;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-xl);
}

.footer {
    padding: var(--spacing-xxl) 0 var(--spacing-lg);
    background: var(--color-bg);
    border-top: 1px solid var(--color-border);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-xxl);
}

.footer-brand {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.footer-logo {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 700;
    letter-spacing: 4px;
    color: var(--color-text);
}

.footer-slogan {
    font-size: 12px;
    letter-spacing: 3px;
    color: var(--color-primary);
}

.footer-links {
    display: flex;
    gap: var(--spacing-xxxl);
}

.footer-column {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.footer-title {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text);
}

.footer-column a {
    font-size: 13px;
    color: var(--color-text-muted);
}

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

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--color-border);
}

.footer-bottom p {
    font-size: 12px;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-xs);
}

@media (max-width: 1024px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .showcase-grid {
        grid-template-columns: repeat(2, 1fr);
        grid-template-rows: repeat(3, 200px);
    }
    
    .showcase-large {
        grid-column: span 2;
        grid-row: span 1;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-xl);
    }
}

@media (max-width: 768px) {
    .nav {
        display: none;
    }
    
    .hero-title {
        font-size: 40px;
        letter-spacing: 6px;
    }
    
    .hero-subtitle {
        font-size: 14px;
        letter-spacing: 4px;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .showcase-grid {
        grid-template-columns: 1fr;
    }
    
    .showcase-large {
        grid-column: span 1;
    }
    
    .footer-content {
        flex-direction: column;
        gap: var(--spacing-xl);
    }
    
    .footer-links {
        flex-wrap: wrap;
        gap: var(--spacing-xl);
    }
}

.page-header {
    padding-top: calc(var(--header-height) + var(--spacing-xxxl));
    padding-bottom: var(--spacing-xxl);
    background: var(--color-bg-light);
    text-align: center;
}

.page-header-title {
    font-size: 36px;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.page-header-desc {
    font-size: 16px;
    color: var(--color-text-muted);
}

.material-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-md);
    padding: var(--spacing-xxl) 0;
}

.material-item {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    overflow: hidden;
    transition: all var(--transition-normal);
    cursor: pointer;
}

.material-item:hover {
    transform: translateY(-5px);
    border-color: var(--color-primary);
    box-shadow: 0 10px 30px rgba(0, 168, 255, 0.2);
}

.material-cover {
    position: relative;
    height: 180px;
    overflow: hidden;
}

.material-cover img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.material-item:hover .material-cover img {
    transform: scale(1.1);
}

.material-tag {
    position: absolute;
    top: var(--spacing-sm);
    right: var(--spacing-sm);
    padding: 4px 10px;
    background: rgba(0, 168, 255, 0.9);
    color: white;
    font-size: 11px;
    font-weight: 600;
    border-radius: var(--radius-sm);
}

.material-info {
    padding: var(--spacing-md);
}

.material-title {
    font-size: 15px;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.material-meta {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    color: var(--color-text-muted);
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
    padding: var(--spacing-xxl) 0;
}

.course-card {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all var(--transition-normal);
    cursor: pointer;
}

.course-card:hover {
    transform: translateY(-5px);
    border-color: var(--color-primary);
}

.course-thumb {
    position: relative;
    height: 180px;
    overflow: hidden;
}

.course-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.course-card:hover .course-thumb img {
    transform: scale(1.1);
}

.course-level {
    position: absolute;
    top: var(--spacing-sm);
    left: var(--spacing-sm);
    padding: 4px 12px;
    background: rgba(0, 0, 0, 0.7);
    color: var(--color-primary);
    font-size: 11px;
    font-weight: 600;
    border-radius: var(--radius-sm);
}

.course-content {
    padding: var(--spacing-lg);
}

.course-title {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    line-height: 1.4;
}

.course-desc {
    font-size: 13px;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-md);
    line-height: 1.5;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    color: var(--color-text-muted);
}

.join-section {
    padding: var(--spacing-xxl) 0;
}

.join-card {
    max-width: 600px;
    margin: 0 auto;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xxl);
    text-align: center;
}

.join-title {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

.join-desc {
    font-size: 15px;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-xl);
    line-height: 1.6;
}

.join-form {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.form-group {
    text-align: left;
}

.form-label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text-light);
}

.form-input,
.form-textarea {
    width: 100%;
    padding: 12px 16px;
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text);
    font-size: 14px;
    font-family: inherit;
    transition: border-color var(--transition-fast);
}

.form-input:focus,
.form-textarea:focus {
    outline: none;
    border-color: var(--color-primary);
}

.form-textarea {
    min-height: 120px;
    resize: vertical;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

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

.animate-fadeIn {
    animation: fadeIn 0.6s ease-out forwards;
}

.animate-slideUp {
    animation: slideUp 0.6s ease-out forwards;
}

.stagger-1 { animation-delay: 0.1s; }
.stagger-2 { animation-delay: 0.2s; }
.stagger-3 { animation-delay: 0.3s; }
.stagger-4 { animation-delay: 0.4s; }

.material-filters {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    justify-content: center;
    padding: var(--spacing-lg) 0;
    margin-bottom: var(--spacing-md);
}

.filter-btn {
    padding: 10px 24px;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text-light);
    font-size: 14px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.filter-btn:hover {
    border-color: var(--color-primary);
    color: var(--color-text);
}

.filter-btn.active {
    background: var(--color-primary);
    border-color: var(--color-primary);
    color: white;
}

.hero-background::before {
    filter: saturate(0.7) contrast(1.15) brightness(0.85);
}

.showcase-cover img {
    filter: saturate(0.7) contrast(1.12) brightness(0.95);
    transition: filter var(--transition-slow), transform var(--transition-slow);
}

.showcase-item:hover .showcase-cover img {
    filter: saturate(0.85) contrast(1.18) brightness(1);
    transform: scale(1.05);
}

.material-cover img {
    filter: saturate(0.75) contrast(1.1) brightness(1);
    transition: filter var(--transition-slow), transform var(--transition-slow);
}

.material-item:hover .material-cover img {
    filter: saturate(0.9) contrast(1.15) brightness(1.05);
    transform: scale(1.08);
}

.course-thumb img {
    filter: saturate(0.7) contrast(1.12) brightness(0.98);
    transition: filter var(--transition-slow), transform var(--transition-slow);
}

.course-card:hover .course-thumb img {
    filter: saturate(0.85) contrast(1.18) brightness(1.02);
    transform: scale(1.05);
}

.feature-card {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, rgba(0, 168, 255, 0.03) 0%, rgba(0, 0, 0, 0) 50%);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.feature-card:hover::before {
    opacity: 1;
}

.stat-number {
    font-family: var(--font-display);
    font-size: 48px;
    font-weight: 700;
    background: linear-gradient(135deg, #e0e0e0 0%, #ffffff 50%, #b0b0b0 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: none;
    letter-spacing: 2px;
}

.hero-title {
    font-family: var(--font-display);
    font-size: 80px;
    font-weight: 900;
    letter-spacing: 12px;
    margin-bottom: var(--spacing-sm);
    background: linear-gradient(135deg, #ffffff 0%, #c0c0c0 50%, #ffffff 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: none;
    filter: drop-shadow(0 0 30px rgba(255, 255, 255, 0.2));
}

.hero-subtitle {
    font-family: var(--font-display);
    font-size: 18px;
    letter-spacing: 8px;
    color: #a0a0a0;
    margin-bottom: var(--spacing-xl);
    text-transform: uppercase;
}

.logo-text {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 700;
    letter-spacing: 4px;
    background: linear-gradient(135deg, #e0e0e0 0%, #ffffff 50%, #c0c0c0 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}