/* Main CSS for AliExpress Dropshipping Website */

/* ========================================
   Basic Reset
======================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* ========================================
   CSS Variables and Reset
======================================== */
:root {
    /* Colors */
    --primary-color: #ff6b35;
    --primary-dark: #e55a2e;
    --primary-light: #ff7a47;
    --secondary-color: #2c3e50;
    --accent-color: #f39c12;
    --success-color: #27ae60;
    --warning-color: #f1c40f;
    --error-color: #e74c3c;
    --info-color: #3498db;
    
    /* Neutral Colors */
    --white: #ffffff;
    --black: #000000;
    --gray-50: #f8f9fa;
    --gray-100: #e9ecef;
    --gray-200: #dee2e6;
    --gray-300: #ced4da;
    --gray-400: #adb5bd;
    --gray-500: #6c757d;
    --gray-600: #495057;
    --gray-700: #343a40;
    --gray-800: #212529;
    --gray-900: #0d1117;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    
    --font-weight-light: 300;
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    
    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
    
    /* Spacing */
    --spacing-1: 0.25rem;
    --spacing-2: 0.5rem;
    --spacing-3: 0.75rem;
    --spacing-4: 1rem;
    --spacing-5: 1.25rem;
    --spacing-6: 1.5rem;
    --spacing-8: 2rem;
    --spacing-10: 2.5rem;
    --spacing-12: 3rem;
    --spacing-16: 4rem;
    --spacing-20: 5rem;
    --spacing-24: 6rem;
    
    /* Breakpoints */
    --breakpoint-sm: 640px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 1024px;
    --breakpoint-xl: 1280px;
    --breakpoint-2xl: 1536px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-base: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 300ms ease-in-out;
    --transition-slow: 500ms ease-in-out;
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-base: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;
    
    /* Z-index */
    --z-dropdown: 1000;
    --z-sticky: 1020;
    --z-fixed: 9999;
    --z-modal: 1040;
    --z-popover: 1060;
    --z-tooltip: 1060;
}

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
    overflow-x: hidden;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    color: var(--gray-800);
    background-color: var(--white);
    margin: 0;
    padding: 0;
    padding-top: 0 !important;
    margin-top: 0 !important;
    position: relative;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

main {
    position: relative;
    z-index: 5;
}

/* ========================================
   Utility Classes
======================================== */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-4);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-3) var(--spacing-6);
    border: none;
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    text-decoration: none;
    cursor: pointer;
    transition: all var(--transition-base);
    white-space: nowrap;
    user-select: none;
    position: relative;
    overflow: hidden;
}

.btn:focus {
    outline: none;
    box-shadow: 0 0 0 3px rgba(255, 107, 53, 0.3);
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: var(--white);
    padding: var(--spacing-4) var(--spacing-8);
    border-radius: var(--radius-full);
    font-size: var(--font-size-lg);
    font-weight: var(--font-weight-semibold);
    box-shadow: 0 4px 15px rgba(255, 107, 53, 0.3);
    position: relative;
    overflow: hidden;
}

.btn-primary::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 0.6s;
}

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

.btn-primary:hover {
    background: linear-gradient(135deg, var(--accent-color), var(--primary-color));
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 107, 53, 0.4);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.15);
    color: var(--white);
    border: 2px solid rgba(255, 255, 255, 0.3);
    padding: var(--spacing-4) var(--spacing-8);
    border-radius: var(--radius-full);
    font-size: var(--font-size-lg);
    font-weight: var(--font-weight-semibold);
    backdrop-filter: blur(10px);
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.btn-secondary::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    opacity: 0;
    transition: opacity var(--transition-base);
    z-index: -1;
}

.btn-secondary:hover::before {
    opacity: 1;
}

.btn-secondary:hover {
    border-color: transparent;
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 107, 53, 0.3);
}

.btn-cta {
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: var(--white);
    padding: var(--spacing-3) var(--spacing-8);
    border-radius: var(--radius-full);
    font-weight: var(--font-weight-semibold);
    text-decoration: none;
    transition: all var(--transition-base);
}

.btn-cta:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl);
}

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

.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }
.d-inline-flex { display: inline-flex; }

/* ========================================
   Header/Navigation Styles
======================================== */
header {
    position: relative;
    z-index: var(--z-fixed);
}

.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: transparent;
    backdrop-filter: none;
    border-bottom: none;
    z-index: var(--z-fixed);
    transition: all var(--transition-base);
}

.navbar.scrolled {
    background-color: transparent;
    box-shadow: none;
}

.navbar.nav-hidden {
    transform: translateY(-100%);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-4) var(--spacing-4);
    max-width: 1200px;
    margin: 0 auto;
}

.nav-logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    flex-shrink: 0;
}

.nav-logo a {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: var(--gray-800);
}

.logo-img {
    height: 36px;
    width: auto;
}

.nav-menu {
    display: flex;
    list-style: none;
    align-items: center;
    gap: var(--spacing-8);
    flex: 1;
    justify-content: center;
}

.nav-item {
    position: relative;
}

.nav-link {
    color: var(--white);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    padding: var(--spacing-2) var(--spacing-4);
    border-radius: var(--radius-md);
    transition: all var(--transition-base);
    white-space: nowrap;
    display: inline-block;
    min-height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
}

.nav-link:hover {
    color: var(--primary-color);
    background-color: rgba(255, 255, 255, 0.2);
    transform: none;
}

/* Dropdown Styles */
.dropdown {
    position: relative;
}

.dropdown-toggle::after {
    content: '▼';
    font-size: var(--font-size-xs);
    margin-left: var(--spacing-2);
    transition: transform var(--transition-base);
}

.dropdown.active .dropdown-toggle::after {
    transform: rotate(180deg);
}

.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    min-width: 200px;
    background-color: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    list-style: none;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-base);
    z-index: var(--z-dropdown);
}

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

.dropdown-menu li {
    border-bottom: 1px solid var(--gray-100);
}

.dropdown-menu li:last-child {
    border-bottom: none;
}

.dropdown-menu a {
    display: block;
    padding: var(--spacing-3) var(--spacing-4);
    color: var(--gray-700);
    text-decoration: none;
    transition: all var(--transition-base);
}

.dropdown-menu a:hover {
    background-color: var(--gray-50);
    color: var(--primary-color);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-4);
    flex-shrink: 0;
}

.login-link {
    color: var(--gray-700);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    padding: var(--spacing-2) var(--spacing-4);
    border-radius: var(--radius-md);
    transition: all var(--transition-base);
    white-space: nowrap;
    min-height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.login-link:hover {
    color: var(--primary-color);
    background-color: var(--gray-50);
    transform: none;
}

/* Mobile Menu Toggle */
.nav-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
    padding: var(--spacing-2);
    gap: var(--spacing-1);
}

.nav-toggle .bar {
    width: 24px;
    height: 3px;
    background-color: var(--white);
    border-radius: var(--radius-full);
    transition: all var(--transition-base);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
}

.nav-toggle.active .bar:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.nav-toggle.active .bar:nth-child(2) {
    opacity: 0;
}

.nav-toggle.active .bar:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
}

/* Button Animations */
@keyframes pulse {
    0% {
        box-shadow: 0 4px 15px rgba(255, 107, 53, 0.4);
    }
    50% {
        box-shadow: 0 4px 25px rgba(255, 107, 53, 0.6);
    }
    100% {
        box-shadow: 0 4px 15px rgba(255, 107, 53, 0.4);
    }
}

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

.hero-buttons .btn-primary {
    animation: pulse 2s infinite;
}

.hero-buttons .btn-primary:hover {
    animation: none;
}

/* ========================================
   Hero Section
======================================== */
.hero-section {
    position: relative;
    height: 100vh;
    display: flex;
    align-items: center;
    overflow: hidden;
}

.hero-content {
    position: relative;
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-16);
    align-items: center;
    z-index: 3;
    padding: calc(80px + var(--spacing-20)) var(--spacing-4) var(--spacing-20);
}

.hero-text {
    text-align: center;
    color: var(--white);
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

.hero-text h1 {
    font-size: var(--font-size-5xl);
    font-weight: var(--font-weight-bold);
    line-height: var(--line-height-tight);
    color: var(--white);
    margin-bottom: var(--spacing-6);
}

.hero-text p {
    font-size: var(--font-size-xl);
    color: rgba(255, 255, 255, 0.9);
    line-height: var(--line-height-relaxed);
    margin-bottom: var(--spacing-8);
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-6);
    flex-wrap: wrap;
    justify-content: center;
    margin-top: var(--spacing-8);
}

.hero-buttons .btn {
    min-width: 160px;
    position: relative;
    z-index: 1;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-weight: var(--font-weight-bold);
}

.hero-buttons .btn:active {
    transform: translateY(-1px);
}

.hero-buttons .btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--accent-color) 100%);
    box-shadow: 0 4px 15px rgba(255, 107, 53, 0.4);
}

.hero-buttons .btn-primary:hover {
    box-shadow: 0 8px 30px rgba(255, 107, 53, 0.5);
    transform: translateY(-4px);
}

.hero-buttons .btn-secondary {
    background: rgba(255, 255, 255, 0.1);
    border: 2px solid rgba(255, 255, 255, 0.4);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.hero-buttons .btn-secondary:hover {
    background: rgba(255, 255, 255, 0.2);
    border-color: rgba(255, 255, 255, 0.6);
    box-shadow: 0 8px 25px rgba(255, 255, 255, 0.2);
}

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

.hero-image::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(0, 0, 0, 0.4) 0%, rgba(0, 0, 0, 0.2) 100%);
    z-index: 2;
    transition: opacity var(--transition-slow);
}

.hero-section:hover .hero-image::before {
    opacity: 0.8;
}

.hero-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    object-position: center;
    border-radius: 0;
    box-shadow: none;
    /* 确保图片在所有浏览器中正确显示 */
    -webkit-object-fit: cover;
    -webkit-object-position: center;
    /* 防止图片拖拽 */
    -webkit-user-drag: none;
    -khtml-user-drag: none;
    -moz-user-drag: none;
    -o-user-drag: none;
    user-select: none;
    /* 提高图片渲染质量 */
    image-rendering: -webkit-optimize-contrast;
    image-rendering: crisp-edges;
}

/* ========================================
   Features Section
======================================== */
.features-section {
    position: relative;
    z-index: 10;
    padding: var(--spacing-24) var(--spacing-4);
    background-color: var(--white);
}

.features-section h2 {
    text-align: center;
    font-size: var(--font-size-4xl);
    font-weight: var(--font-weight-bold);
    color: var(--gray-800);
    margin-bottom: var(--spacing-16);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: var(--spacing-8);
    max-width: 1200px;
    margin: 0 auto;
}

.feature-card {
    background-color: var(--white);
    padding: var(--spacing-8);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-base);
    text-align: center;
    transition: all var(--transition-base);
    border: 1px solid var(--gray-100);
    position: relative;
    overflow: hidden;
    min-height: 280px;
    display: flex;
    align-items: flex-end;
}

/* 带背景图片的特色卡片样式 */
.feature-card-with-bg {
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    color: white;
}

/* 为背景图片添加深色遮罩，确保文字可读性 */
.feature-card-with-bg::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(
        180deg, 
        rgba(0, 0, 0, 0.3) 0%, 
        rgba(0, 0, 0, 0.7) 100%
    );
    z-index: 1;
}

/* 文字内容容器 */
.feature-content {
    position: relative;
    z-index: 2;
    width: 100%;
    padding: var(--spacing-6);
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-color);
}

/* 带背景图片的卡片悬停效果 */
.feature-card-with-bg:hover {
    transform: translateY(-12px);
    box-shadow: var(--shadow-2xl);
}

.feature-card-with-bg:hover::before {
    background: linear-gradient(
        180deg, 
        rgba(0, 0, 0, 0.2) 0%, 
        rgba(0, 0, 0, 0.6) 100%
    );
}

.feature-icon {
    width: 80px;
    height: 80px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-6);
}

.feature-icon i {
    font-size: var(--font-size-3xl);
    color: var(--white);
}

.feature-icon .feature-img {
    width: 48px;
    height: 48px;
    object-fit: contain;
    filter: brightness(0) invert(1); /* 将图片变为白色 */
}

.feature-card h3 {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
    color: var(--gray-800);
    margin-bottom: var(--spacing-4);
}

.feature-card p {
    color: var(--gray-600);
    line-height: var(--line-height-relaxed);
}

/* 带背景图片的卡片文字样式 */
.feature-card-with-bg h3 {
    color: white;
    font-weight: var(--font-weight-bold);
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.5);
    margin-bottom: var(--spacing-3);
}

.feature-card-with-bg p {
    color: rgba(255, 255, 255, 0.95);
    text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.5);
    line-height: var(--line-height-relaxed);
}

/* ========================================
   How It Works Section
======================================== */
.how-it-works-section {
    position: relative;
    z-index: 10;
    padding: var(--spacing-24) var(--spacing-4);
    background: linear-gradient(135deg, var(--gray-50) 0%, var(--white) 100%);
}

.how-it-works-section h2 {
    text-align: center;
    font-size: var(--font-size-4xl);
    font-weight: var(--font-weight-bold);
    color: var(--gray-800);
    margin-bottom: var(--spacing-16);
}

.steps-container {
    max-width: 1000px;
    margin: 0 auto;
    display: grid;
    gap: var(--spacing-12);
}

.step {
    display: flex;
    align-items: center;
    gap: var(--spacing-8);
    position: relative;
}

.step:nth-child(even) {
    flex-direction: row-reverse;
}

.step:not(:last-child)::after {
    content: '';
    position: absolute;
    left: 50%;
    bottom: -50px;
    transform: translateX(-50%);
    width: 2px;
    height: 40px;
    background: linear-gradient(to bottom, var(--primary-color), var(--accent-color));
}

.step-number {
    width: 80px;
    height: 80px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: var(--white);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: var(--font-size-2xl);
    font-weight: var(--font-weight-bold);
    flex-shrink: 0;
    box-shadow: var(--shadow-lg);
}

.step-content {
    flex: 1;
    padding: var(--spacing-6);
    background-color: var(--white);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-base);
    border: 1px solid var(--gray-100);
}

.step-content h3 {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
    color: var(--gray-800);
    margin-bottom: var(--spacing-4);
}

.step-content p {
    color: var(--gray-600);
    line-height: var(--line-height-relaxed);
}

/* ========================================
   Statistics Section
======================================== */
.stats-section {
    position: relative;
    z-index: 10;
    padding: var(--spacing-20) var(--spacing-4);
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: var(--white);
}

.stats-grid {
    max-width: 1000px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-8);
    text-align: center;
}

.stat-item h3 {
    font-size: var(--font-size-5xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-2);
}

.stat-item p {
    font-size: var(--font-size-lg);
    opacity: 0.9;
}

/* ========================================
   CTA Section
======================================== */
.cta-section {
    position: relative;
    z-index: 10;
    padding: var(--spacing-24) var(--spacing-4);
    background-color: var(--gray-900);
    color: var(--white);
    text-align: center;
}

.cta-section h2 {
    font-size: var(--font-size-4xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-6);
}

.cta-section p {
    font-size: var(--font-size-xl);
    opacity: 0.9;
    margin-bottom: var(--spacing-8);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.cta-buttons {
    display: flex;
    gap: var(--spacing-4);
    justify-content: center;
    flex-wrap: wrap;
}

/* ========================================
   Language Switcher
======================================== */
.language-switcher {
    position: fixed;
    bottom: var(--spacing-6);
    right: var(--spacing-6);
    z-index: var(--z-fixed);
}

.lang-btn {
    background-color: var(--white);
    border: 2px solid var(--primary-color);
    border-radius: var(--radius-full);
    padding: var(--spacing-3) var(--spacing-4);
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    cursor: pointer;
    color: var(--primary-color);
    font-weight: var(--font-weight-medium);
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-base);
}

.lang-btn:hover {
    background-color: var(--primary-color);
    color: var(--white);
}

.lang-dropdown {
    position: absolute;
    bottom: 100%;
    right: 0;
    background-color: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: all var(--transition-base);
    min-width: 180px;
    max-height: 300px;
    overflow-y: auto;
    margin-bottom: var(--spacing-2);
    z-index: calc(var(--z-fixed) + 1);
}

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

.lang-option {
    display: block;
    width: 100%;
    padding: var(--spacing-2) var(--spacing-4);
    border: none;
    background: none;
    text-align: left;
    color: var(--gray-700);
    cursor: pointer;
    transition: all var(--transition-base);
    border-bottom: 1px solid var(--gray-100);
    font-size: var(--font-size-sm);
    white-space: nowrap;
}

.lang-option:last-child {
    border-bottom: none;
}

.lang-option:hover,
.lang-option.active {
    background-color: var(--primary-color);
    color: var(--white);
}

/* ========================================
   Back to Top Button
======================================== */
.back-to-top {
    position: fixed;
    bottom: var(--spacing-6);
    left: var(--spacing-6);
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border: none;
    border-radius: var(--radius-full);
    color: var(--white);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition-base);
    box-shadow: var(--shadow-lg);
    z-index: var(--z-fixed);
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-xl);
}

.back-to-top i {
    font-size: var(--font-size-lg);
}

/* ========================================
   Loading States
======================================== */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: var(--white);
    animation: spin 1s ease-in-out infinite;
}

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

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

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

/* ========================================
   Print Styles
======================================== */
@media print {
    .navbar,
    .language-switcher,
    .back-to-top,
    .btn {
        display: none !important;
    }
    
    body {
        font-size: 12pt;
        line-height: 1.4;
    }
    
    .hero-section,
    .features-section,
    .how-it-works-section,
    .stats-section,
    .cta-section {
        padding: 20pt 0;
        page-break-inside: avoid;
    }
}