/* ============================================
   现代瀑布流网站 - 完整CSS样式文件
   布局：B. 卡片式瀑布流
   风格：毛玻璃 + 渐变 + 几何装饰
   ============================================ */

/* ============================================
   1. CSS 变量定义
   ============================================ */
:root {
    /* 主色调 */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --accent-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    
    /* 毛玻璃效果 */
    --glass-bg: rgba(255, 255, 255, 0.1);
    --glass-border: rgba(255, 255, 255, 0.2);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    
    /* 颜色系统 */
    --primary: #667eea;
    --primary-dark: #5568d3;
    --secondary: #764ba2;
    --accent: #4facfe;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    
    /* 背景色 */
    --bg-dark: #0f0f23;
    --bg-darker: #070714;
    --bg-card: rgba(255, 255, 255, 0.05);
    
    /* 文字颜色 */
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --text-muted: rgba(255, 255, 255, 0.5);
    
    /* 间距系统 */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    
    /* 圆角 */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;
    
    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.15);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.2);
    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.4);
    
    /* 过渡 */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* 字体 */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-display: 'Poppins', var(--font-sans);
}

/* ============================================
   2. 全局重置与基础样式
   ============================================ */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-dark);
    background-image: 
        radial-gradient(ellipse at 20% 20%, rgba(102, 126, 234, 0.15) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(118, 75, 162, 0.15) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, rgba(79, 172, 254, 0.05) 0%, transparent 70%);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

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

ul, ol {
    list-style: none;
}

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

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

input, textarea, select {
    font-family: inherit;
    font-size: inherit;
}

/* ============================================
   3. 滚动条样式
   ============================================ */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-darker);
}

::-webkit-scrollbar-thumb {
    background: var(--primary);
    border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary-dark);
}

/* ============================================
   4. 布局容器
   ============================================ */
.container {
    width: 100%;
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

.section {
    padding: var(--space-3xl) 0;
}

/* ============================================
   5. 导航栏
   ============================================ */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: var(--space-md) 0;
    background: rgba(15, 15, 35, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--glass-border);
    transition: all var(--transition-normal);
}

.navbar.scrolled {
    padding: var(--space-sm) 0;
    background: rgba(15, 15, 35, 0.95);
}

.navbar-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    font-family: var(--font-display);
    font-size: 1.75rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: var(--primary-gradient);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: var(--space-xl);
}

.nav-link {
    font-weight: 500;
    color: var(--text-secondary);
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--primary-gradient);
    transition: all var(--transition-normal);
    transform: translateX(-50%);
    border-radius: var(--radius-full);
}

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

.nav-link:hover::after {
    width: 60%;
}

.nav-link.active {
    color: var(--text-primary);
    background: var(--glass-bg);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.mobile-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: var(--space-sm);
}

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

/* ============================================
   6. 按钮样式
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-xl);
    font-weight: 600;
    font-size: 0.95rem;
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s ease;
}

.btn:hover::before {
    left: 100%;
}

.btn-primary {
    background: var(--primary-gradient);
    color: white;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.5);
}

.btn-secondary {
    background: var(--glass-bg);
    color: var(--text-primary);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(10px);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.15);
    border-color: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

.btn-ghost {
    background: transparent;
    color: var(--text-secondary);
}

.btn-ghost:hover {
    color: var(--text-primary);
    background: var(--glass-bg);
}

.btn-icon {
    width: 44px;
    height: 44px;
    padding: 0;
    border-radius: var(--radius-md);
}

.btn-sm {
    padding: var(--space-sm) var(--space-md);
    font-size: 0.875rem;
}

.btn-lg {
    padding: var(--space-lg) var(--space-2xl);
    font-size: 1.1rem;
}

/* ============================================
   7. 卡片样式 - 瀑布流
   ============================================ */
.masonry-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-lg);
    grid-auto-flow: dense;
}

.card {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all var(--transition-normal);
    position: relative;
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    border-color: rgba(102, 126, 234, 0.3);
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--primary-gradient);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

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

/* 卡片尺寸变体 - 瀑布流效果 */
.card-tall {
    grid-row: span 2;
}

.card-wide {
    grid-column: span 2;
}

.card-featured {
    grid-column: span 2;
    grid-row: span 2;
}

.card-image {
    position: relative;
    overflow: hidden;
    aspect-ratio: 16 / 10;
}

.card-tall .card-image {
    aspect-ratio: 10 / 16;
}

.card-wide .card-image {
    aspect-ratio: 21 / 9;
}

.card-featured .card-image {
    aspect-ratio: 1;
}

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

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

.card-overlay {
    position: absolute;
    inset: 0;
    background: linear-gradient(to top, rgba(0, 0, 0, 0.7) 0%, transparent 50%);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.card:hover .card-overlay {
    opacity: 1;
}

.card-badge {
    position: absolute;
    top: var(--space-md);
    left: var(--space-md);
    padding: var(--space-xs) var(--space-sm);
    background: var(--secondary-gradient);
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: var(--radius-full);
}

.card-content {
    padding: var(--space-lg);
}

.card-category {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-sm);
}

.card-title {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 700;
    line-height: 1.3;
    margin-bottom: var(--space-md);
    background: linear-gradient(to right, var(--text-primary), var(--text-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.card-featured .card-title {
    font-size: 2rem;
}

.card-excerpt {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.7;
    margin-bottom: var(--space-lg);
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.card-meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--space-md);
    border-top: 1px solid var(--glass-border);
}

.card-author {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.card-avatar {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-full);
    background: var(--accent-gradient);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.875rem;
}

.card-author-name {
    font-weight: 500;
    font-size: 0.875rem;
}

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

.card-stats {
    display: flex;
    gap: var(--space-md);
}

.card-stat {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* ============================================
   8. Hero 区域
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: 80px;
    position: relative;
    overflow: hidden;
}

.hero-bg-elements {
    position: absolute;
    inset: 0;
    overflow: hidden;
    pointer-events: none;
}

.hero-shape {
    position: absolute;
    border-radius: var(--radius-full);
    filter: blur(60px);
    opacity: 0.5;
    animation: float 20s ease-in-out infinite;
}

.hero-shape-1 {
    width: 400px;
    height: 400px;
    background: var(--primary);
    top: 10%;
    right: 10%;
}

.hero-shape-2 {
    width: 300px;
    height: 300px;
    background: var(--secondary);
    bottom: 20%;
    left: 15%;
    animation-delay: -5s;
}

.hero-shape-3 {
    width: 200px;
    height: 200px;
    background: var(--accent);
    top: 40%;
    left: 50%;
    animation-delay: -10s;
}

@keyframes float {
    0%, 100% {
        transform: translate(0, 0) scale(1);
    }
    25% {
        transform: translate(30px, -30px) scale(1.05);
    }
    50% {
        transform: translate(-20px, 20px) scale(0.95);
    }
    75% {
        transform: translate(20px, 30px) scale(1.02);
    }
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}

.hero-tag {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-full);
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-xl);
    backdrop-filter: blur(10px);
}

.hero-tag-dot {
    width: 8px;
    height: 8px;
    background: var(--success);
    border-radius: var(--radius-full);
    animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.5;
    }
}

.hero-title {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 6vw, 4.5rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: var(--space-xl);
}

.hero-title-gradient {
    background: linear-gradient(135deg, #fff 0%, #a5b4fc 50%, #667eea 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-description {
    font-size: 1.25rem;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: var(--space-2xl);
    max-width: 600px;
}

.hero-actions {
    display: flex;
    gap: var(--space-md);
    flex-wrap: wrap;
}

.hero-stats {
    display: flex;
    gap: var(--space-2xl);
    margin-top: var(--space-3xl);
    padding-top: var(--space-2xl);
    border-top: 1px solid var(--glass-border);
}

.hero-stat {
    text-align: center;
}

.hero-stat-value {
    font-family: var(--font-display);
    font-size: 2.5rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-stat-label {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-top: var(--space-xs);
}

/* ============================================
   9. 表单样式
   ============================================ */
.form-group {
    margin-bottom: var(--space-lg);
}

.form-label {
    display: block;
    font-weight: 500;
    margin-bottom: var(--space-sm);
    color: var(--text-secondary);
}

.form-input {
    width: 100%;
    padding: var(--space-md) var(--space-lg);
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    color: var(--text-primary);
    transition: all var(--transition-fast);
    backdrop-filter: blur(10px);
}

.form-input::placeholder {
    color: var(--text-muted);
}

.form-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.2);
}

.form-input:hover:not(:focus) {
    border-color: rgba(255, 255, 255, 0.3);
}

textarea.form-input {
    min-height: 150px;
    resize: vertical;
}

.form-select {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23ffffff' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6,9 12,15 18,9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right var(--space-md) center;
    background-size: 16px;
    padding-right: var(--space-2xl);
}

.form-checkbox {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    cursor: pointer;
}

.form-checkbox input {
    width: 20px;
    height: 20px;
    border: 2px solid var(--glass-border);
    border-radius: var(--radius-sm);
    background: var(--glass-bg);
    cursor: pointer;
    transition: all var(--transition-fast);
    appearance: none;
    display: flex;
    align-items: center;
    justify-content: center;
}

.form-checkbox input:checked {
    background: var(--primary-gradient);
    border-color: transparent;
}

.form-checkbox input:checked::after {
    content: '✓';
    color: white;
    font-size: 0.75rem;
    font-weight: bold;
}

.form-search {
    position: relative;
}

.form-search-icon {
    position: absolute;
    left: var(--space-lg);
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
}

.form-search .form-input {
    padding-left: calc(var(--space-lg) * 2 + 20px);
}

/* ============================================
   10. 几何装饰元素
   ============================================ */
.decorative-shapes {
    position: absolute;
    pointer-events: none;
}

.shape-circle {
    border-radius: var(--radius-full);
    border: 2px solid var(--glass-border);
}

.shape-square {
    border: 2px solid var(--glass-border);
    transform: rotate(45deg);
}

.shape-line {
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--primary), transparent);
}

.floating-elements {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: -1;
}

.floating-icon {
    position: absolute;
    opacity: 0.1;
    animation: floatIcon 15s ease-in-out infinite;
}

.floating-icon:nth-child(1) { top: 20%; left: 10%; animation-delay: 0s; }
.floating-icon:nth-child(2) { top: 60%; left: 5%; animation-delay: -3s; }
.floating-icon:nth-child(3) { top: 80%; left: 15%; animation-delay: -6s; }
.floating-icon:nth-child(4) { top: 30%; right: 10%; animation-delay: -9s; }
.floating-icon:nth-child(5) { top: 70%; right: 5%; animation-delay: -12s; }

@keyframes floatIcon {
    0%, 100% {
        transform: translate(0, 0) rotate(0deg);
    }
    25% {
        transform: translate(20px, -20px) rotate(90deg);
    }
    50% {
        transform: translate(-10px, 10px) rotate(180deg);
    }
    75% {
        transform: translate(15px, -15px) rotate(270deg);
    }
}

/* ============================================
   11. 特色区块
   ============================================ */
.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.feature-card {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-xl);
    padding: var(--space-2xl);
    text-align: center;
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-10px);
    border-color: rgba(102, 126, 234, 0.3);
    box-shadow: var(--shadow-glow);
}

.feature-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--space-lg);
    background: var(--primary-gradient);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    transition: transform var(--transition-normal);
}

.feature-card:hover .feature-icon {
    transform: scale(1.1) rotate(5deg);
}

.feature-title {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: var(--space-md);
}

.feature-description {
    color: var(--text-secondary);
    line-height: 1.7;
}

/* ============================================
   12. 页脚
   ============================================ */
.footer {
    background: var(--bg-darker);
    border-top: 1px solid var(--glass-border);
    padding: var(--space-3xl) 0 var(--space-xl);
    margin-top: var(--space-3xl);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr repeat(3, 1fr);
    gap: var(--space-2xl);
    margin-bottom: var(--space-2xl);
}

.footer-brand {
    max-width: 300px;
}

.footer-brand .logo {
    margin-bottom: var(--space-lg);
}

.footer-description {
    color: var(--text-muted);
    line-height: 1.7;
    margin-bottom: var(--space-lg);
}

.footer-social {
    display: flex;
    gap: var(--space-md);
}

.social-link {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.social-link:hover {
    background: var(--primary-gradient);
    border-color: transparent;
    color: white;
    transform: translateY(-3px);
}

.footer-column h4 {
    font-family: var(--font-display);
    font-weight: 600;
    margin-bottom: var(--space-lg);
    color: var(--text-primary);
}

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

.footer-link {
    color: var(--text-muted);
    transition: color var(--transition-fast);
}

.footer-link:hover {
    color: var(--text-primary);
}

.footer-bottom {
    padding-top: var(--space-xl);
    border-top: 1px solid var(--glass-border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--space-md);
}

.footer-copyright {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.footer-legal {
    display: flex;
    gap: var(--space-lg);
}

.footer-legal a {
    color: var(--text-muted);
    font-size: 0.9rem;
}

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

/* ============================================
   13. 加载动画
   ============================================ */
.loading-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--glass-border);
    border-top-color: var(--primary);
    border-radius: var(--radius-full);
    animation: spin 1s linear infinite;
}

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

.skeleton {
    background: linear-gradient(
        90deg,
        var(--glass-bg) 25%,
        rgba(255, 255, 255, 0.1) 50%,
        var(--glass-bg) 75%
    );
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    border-radius: var(--radius-md);
}

@keyframes shimmer {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

/* ============================================
   14. 工具类
   ============================================ */
.text-gradient {
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-sm { gap: var(--space-sm); }
.gap-md { gap: var(--space-md); }
.gap-lg { gap: var(--space-lg); }

.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }

.hidden { display: none; }
.visible { visibility: visible; }
.invisible { visibility: hidden; }

/* ============================================
   15. 响应式设计
   ============================================ */

/* 平板横屏 */
@media (max-width: 1200px) {
    .masonry-grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .card-wide {
        grid-column: span 1;
    }
    
    .card-featured {
        grid-column: span 2;
        grid-row: span 1;
    }
    
    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* 平板竖屏 */
@media (max-width: 992px) {
    :root {
        --space-lg: 1.25rem;
        --space-xl: 1.5rem;
        --space-2xl: 2rem;
    }
    
    .hero-title {
        font-size: clamp(2rem, 5vw, 3rem);
    }
    
    .hero-stats {
        gap: var(--space-xl);
    }
    
    .hero-stat-value {
        font-size: 2rem;
    }
    
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .nav-menu {
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        background: rgba(15, 15, 35, 0.98);
        backdrop-filter: blur(20px);
        flex-direction: column;
        justify-content: center;
        gap: var(--space-xl);
        transform: translateX(-100%);
        transition: transform var(--transition-normal);
        z-index: 999;
    }
    
    .nav-menu.active {
        transform: translateX(0);
    }
    
    .nav-link {
        font-size: 1.5rem;
    }
    
    .mobile-toggle {
        display: flex;
        z-index: 1001;
    }
    
    .mobile-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    
    .mobile-toggle.active span:nth-child(2) {
        opacity: 0;
    }
    
    .mobile-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }
}

/* 大手机 */
@media (max-width: 768px) {
    :root {
        --space-lg: 1rem;
        --space-xl: 1.25rem;
        --space-2xl: 1.5rem;
    }
    
    .container {
        padding: 0 var(--space-md);
    }
    
    .masonry-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--space-md);
    }
    
    .card-title {
        font-size: 1.2rem;
    }
    
    .card-featured {
        grid-column: span 2;
    }
    
    .hero-stats {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .footer-brand {
        max-width: 100%;
    }
    
    .footer-social {
        justify-content: center;
    }
    
    .footer-bottom {
        flex-direction: column;
        text-align: center;
    }
    
    .hero-actions {
        flex-direction: column;
    }
    
    .hero-actions .btn {
        width: 100%;
    }
}

/* 小手机 */
@media (max-width: 480px) {
    .masonry-grid {
        grid-template-columns: 1fr;
    }
    
    .card-wide,
    .card-featured {
        grid-column: span 1;
    }
    
    .card-tall {
        grid-row: span 1;
    }
    
    .card-tall .card-image {
        aspect-ratio: 16 / 10;
    }
    
    .hero-stat-value {
        font-size: 1.75rem;
    }
    
    .btn {
        padding: var(--space-sm) var(--space-lg);
    }
    
    .card-content {
        padding: var(--space-md);
    }
}

/* ============================================
   16. 打印样式
   ============================================ */
@media print {
    .navbar,
    .hero-bg-elements,
    .floating-elements,
    .btn,
    .card-overlay {
        display: none !important;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .card {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ddd;
    }
}
```