/* ===== CSS Reset & Base ===== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary: #0a4d9e;
    --primary-dark: #06336e;
    --primary-light: #1a6fd0;
    --accent: #00b894;
    --accent-dark: #00896d;
    --danger: #e74c3c;
    --warning: #f39c12;
    --dark: #1a1a2e;
    --gray-900: #16213e;
    --gray-700: #4a5568;
    --gray-500: #718096;
    --gray-300: #cbd5e0;
    --gray-100: #f7fafc;
    --gray-50: #f0f4f8;
    --white: #ffffff;
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 30px rgba(0,0,0,0.15);
    --shadow-xl: 0 20px 50px rgba(0,0,0,0.2);
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --transition: all 0.3s ease;
    --max-width: 1200px;
}

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

body {
    font-family: "Microsoft YaHei", "PingFang SC", "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: var(--gray-700);
    background: var(--white);
    overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
    color: var(--gray-900);
}

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

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

ul {
    list-style: none;
}

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

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 28px;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
    white-space: nowrap;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-outline {
    background: transparent;
    color: var(--primary);
    border-color: var(--primary);
}

.btn-outline:hover {
    background: var(--primary);
    color: var(--white);
    transform: translateY(-2px);
}

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

.btn-white:hover {
    background: var(--gray-100);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-lg {
    padding: 16px 36px;
    font-size: 1.05rem;
}

/* ===== Header / Navigation ===== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--primary);
}

.nav-logo-icon {
    width: 38px;
    height: 38px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.nav-logo-icon svg {
    width: 38px;
    height: 38px;
    display: block;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: 22px;
}

.nav-menu a {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--gray-700);
    position: relative;
    padding: 5px 0;
}

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

.nav-menu a:hover {
    color: var(--primary);
}

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

.nav-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.nav-login {
    padding: 8px 24px;
    background: var(--primary);
    color: var(--white);
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 600;
    transition: var(--transition);
}

.nav-login:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.lang-switch {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--gray-500);
    padding: 6px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.lang-switch:hover {
    color: var(--primary);
    border-color: var(--primary);
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
    padding: 5px;
    background: none;
    border: none;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--primary);
    border-radius: 2px;
    transition: var(--transition);
}

.hamburger.active span:nth-child(1) {
    transform: rotate(45deg) translate(6px, 6px);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg) translate(6px, -6px);
}

/* ===== Hero Section ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    position: relative;
    background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary) 50%, var(--primary-light) 100%);
    overflow: hidden;
    padding-top: 70px;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: 
        radial-gradient(circle at 20% 50%, rgba(255,255,255,0.05) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(0,184,148,0.08) 0%, transparent 50%);
}

.hero-bg-pattern {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    opacity: 0.06;
    background-image: 
        linear-gradient(rgba(255,255,255,0.1) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255,255,255,0.1) 1px, transparent 1px);
    background-size: 50px 50px;
}

.hero-content {
    position: relative;
    z-index: 2;
    color: var(--white);
    max-width: 700px;
    padding: 40px 0;
}

.hero-badge {
    display: inline-block;
    padding: 6px 16px;
    background: rgba(0, 184, 148, 0.2);
    border: 1px solid rgba(0, 184, 148, 0.4);
    border-radius: 20px;
    font-size: 0.85rem;
    color: #5eead4;
    margin-bottom: 24px;
}

.hero h1 {
    font-size: 3rem;
    color: var(--white);
    margin-bottom: 20px;
    line-height: 1.2;
}

.hero h1 span {
    background: linear-gradient(90deg, #5eead4, #00b894);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero p {
    font-size: 1.15rem;
    color: rgba(255, 255, 255, 0.85);
    margin-bottom: 32px;
    line-height: 1.8;
}

.hero-actions {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.hero-stats {
    display: flex;
    gap: 40px;
    margin-top: 50px;
    padding-top: 40px;
    border-top: 1px solid rgba(255, 255, 255, 0.15);
}

.hero-stat-number {
    font-size: 2.2rem;
    font-weight: 700;
    color: var(--white);
}

.hero-stat-label {
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.7);
    margin-top: 4px;
}

/* ===== Section Common ===== */
.section {
    padding: 80px 0;
}

.section-gray {
    background: var(--gray-50);
}

.section-dark {
    background: var(--dark);
    color: rgba(255, 255, 255, 0.8);
}

.section-header {
    text-align: center;
    max-width: 700px;
    margin: 0 auto 60px;
}

.section-tag {
    display: inline-block;
    padding: 4px 16px;
    background: rgba(10, 77, 158, 0.1);
    color: var(--primary);
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 16px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.section-dark .section-tag {
    background: rgba(0, 184, 148, 0.15);
    color: #5eead4;
}

.section-header h2 {
    font-size: 2.2rem;
    margin-bottom: 16px;
}

.section-header p {
    font-size: 1.05rem;
    color: var(--gray-500);
}

.section-dark .section-header h2,
.section-dark .section-header p {
    color: rgba(255, 255, 255, 0.9);
}

/* ===== About Section ===== */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.about-text h2 {
    font-size: 2rem;
    margin-bottom: 20px;
}

.about-text p {
    margin-bottom: 16px;
    font-size: 1.05rem;
    line-height: 1.8;
}

.about-features {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-top: 30px;
}

.about-feature {
    display: flex;
    align-items: flex-start;
    gap: 12px;
}

.about-feature-icon {
    width: 44px;
    height: 44px;
    background: rgba(10, 77, 158, 0.1);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    font-size: 1.3rem;
}

.about-feature h4 {
    font-size: 1rem;
    margin-bottom: 4px;
}

.about-feature p {
    font-size: 0.88rem;
    color: var(--gray-500);
    margin: 0;
}

.about-visual {
    position: relative;
}

.about-visual-card {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    border-radius: var(--radius-lg);
    padding: 50px;
    color: var(--white);
    text-align: center;
    box-shadow: var(--shadow-xl);
}

.about-visual-card h3 {
    color: var(--white);
    font-size: 1.5rem;
    margin-bottom: 20px;
}

.about-visual-card p {
    color: rgba(255, 255, 255, 0.8);
    font-size: 1.1rem;
    margin-bottom: 30px;
}

.about-visual-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
}

.about-visual-tag {
    padding: 8px 20px;
    background: rgba(255, 255, 255, 0.15);
    border-radius: 20px;
    font-size: 0.9rem;
    color: var(--white);
}

/* ===== Products Section ===== */
.products-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.product-card {
    background: var(--white);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    border: 1px solid var(--gray-100);
}

.product-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
}

.product-card-header {
    padding: 40px 30px 30px;
    text-align: center;
    position: relative;
}

.product-card-header.bg-blue {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
}

.product-card-header.bg-green {
    background: linear-gradient(135deg, var(--accent-dark), var(--accent));
}

.product-card-header.bg-purple {
    background: linear-gradient(135deg, #4a154b, #8e44ad);
}

.product-card-icon {
    width: 70px;
    height: 70px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    font-size: 2rem;
}

.product-card-header h3 {
    color: var(--white);
    font-size: 1.4rem;
    margin-bottom: 8px;
}

.product-card-header p {
    color: rgba(255, 255, 255, 0.85);
    font-size: 0.95rem;
}

.product-card-body {
    padding: 30px;
}

.product-card-body h4 {
    font-size: 1rem;
    color: var(--gray-900);
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--gray-100);
}

.product-card-body ul {
    margin-bottom: 24px;
}

.product-card-body ul li {
    padding: 6px 0 6px 24px;
    position: relative;
    font-size: 0.9rem;
    color: var(--gray-700);
    line-height: 1.6;
}

.product-card-body ul li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--accent);
    font-weight: 700;
}

.product-card-footer {
    padding: 0 30px 30px;
}

/* ===== Product Detail Section ===== */
.product-detail {
    padding: 80px 0;
    overflow: hidden;
}

.product-detail.bg-light {
    background: var(--gray-50);
}

.product-detail-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.product-detail-grid.reverse {
    direction: rtl;
}

.product-detail-grid.reverse > * {
    direction: ltr;
}

.product-detail-text h2 {
    font-size: 2rem;
    margin-bottom: 12px;
}

.product-detail-subtitle {
    font-size: 1.1rem;
    color: var(--primary);
    font-weight: 600;
    margin-bottom: 20px;
}

.product-detail-text p {
    margin-bottom: 16px;
    font-size: 1rem;
    line-height: 1.8;
}

.product-features-list {
    margin-top: 24px;
}

.product-feature-item {
    display: flex;
    align-items: flex-start;
    gap: 16px;
    margin-bottom: 20px;
}

.product-feature-item-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    font-size: 1.4rem;
}

.product-feature-item-icon.bg-primary {
    background: rgba(10, 77, 158, 0.1);
    color: var(--primary);
}

.product-feature-item-icon.bg-accent {
    background: rgba(0, 184, 148, 0.1);
    color: var(--accent);
}

.product-feature-item-icon.bg-purple {
    background: rgba(142, 68, 173, 0.1);
    color: #8e44ad;
}

.product-feature-item h4 {
    font-size: 1.05rem;
    margin-bottom: 4px;
}

.product-feature-item p {
    font-size: 0.9rem;
    color: var(--gray-500);
    margin: 0;
}

.product-detail-visual {
    background: var(--white);
    border-radius: var(--radius-lg);
    padding: 40px;
    box-shadow: var(--shadow-lg);
}

.product-detail-visual.bg-gradient-blue {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-light));
    color: var(--white);
}

.product-detail-visual.bg-gradient-green {
    background: linear-gradient(135deg, var(--accent-dark), #00d4aa);
    color: var(--white);
}

.product-detail-visual.bg-gradient-purple {
    background: linear-gradient(135deg, #4a154b, #9b59b6);
    color: var(--white);
}

.visual-content h3 {
    color: var(--white);
    font-size: 1.4rem;
    margin-bottom: 24px;
    text-align: center;
}

.visual-items {
    display: grid;
    gap: 14px;
}

.visual-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 18px;
    background: rgba(255, 255, 255, 0.12);
    border-radius: var(--radius-sm);
    color: var(--white);
    font-size: 0.92rem;
    transition: var(--transition);
}

.visual-item:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateX(4px);
}

.visual-item-icon {
    font-size: 1.2rem;
    flex-shrink: 0;
}

/* ===== Comparison Table ===== */
.comparison-wrapper {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.comparison-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--white);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    min-width: 600px;
}

.comparison-table th,
.comparison-table td {
    padding: 18px 24px;
    text-align: left;
    border-bottom: 1px solid var(--gray-100);
}

.comparison-table th {
    background: var(--gray-50);
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--gray-900);
}

.comparison-table th.col-traditional {
    color: var(--gray-500);
}

.comparison-table th.col-anronghe {
    background: var(--primary);
    color: var(--white);
}

.comparison-table td.col-traditional {
    color: var(--gray-500);
}

.comparison-table td.col-anronghe {
    background: rgba(10, 77, 158, 0.03);
    font-weight: 500;
    color: var(--primary-dark);
}

.comparison-table tr:last-child th,
.comparison-table tr:last-child td {
    border-bottom: none;
}

.comparison-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    font-size: 0.75rem;
    margin-right: 8px;
}

.comparison-icon.no {
    background: rgba(231, 76, 60, 0.1);
    color: var(--danger);
}

.comparison-icon.yes {
    background: rgba(0, 184, 148, 0.1);
    color: var(--accent);
}

/* ===== Value Section ===== */
.value-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.value-card {
    text-align: center;
    padding: 40px 30px;
    border-radius: var(--radius-lg);
    transition: var(--transition);
}

.value-card.bg-light {
    background: var(--white);
    border: 1px solid var(--gray-100);
}

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

.value-icon {
    width: 70px;
    height: 70px;
    margin: 0 auto 24px;
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: var(--white);
}

.value-card h3 {
    font-size: 1.25rem;
    margin-bottom: 12px;
}

.value-card p {
    font-size: 0.95rem;
    color: var(--gray-500);
    line-height: 1.7;
}

/* ===== CTA Section ===== */
.cta {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    padding: 80px 0;
    text-align: center;
    color: var(--white);
    position: relative;
    overflow: hidden;
}

.cta::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: radial-gradient(circle at 30% 50%, rgba(0,184,148,0.15) 0%, transparent 50%);
}

.cta-content {
    position: relative;
    z-index: 2;
}

.cta h2 {
    color: var(--white);
    font-size: 2.2rem;
    margin-bottom: 16px;
}

.cta p {
    font-size: 1.1rem;
    color: rgba(255, 255, 255, 0.85);
    margin-bottom: 32px;
}

.cta-actions {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
}

.cta-phone {
    margin-top: 30px;
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--white);
}

.cta-phone a {
    color: #5eead4;
}

/* ===== Footer ===== */
.footer {
    background: var(--dark);
    color: rgba(255, 255, 255, 0.6);
    padding: 60px 0 0;
}

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

.footer-brand .nav-logo {
    color: var(--white);
    margin-bottom: 16px;
}

.footer-brand p {
    font-size: 0.9rem;
    line-height: 1.7;
    margin-bottom: 16px;
}

.footer-col h4 {
    color: var(--white);
    font-size: 1rem;
    margin-bottom: 20px;
}

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

.footer-col ul li a {
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.6);
    transition: var(--transition);
}

.footer-col ul li a:hover {
    color: var(--white);
}

.footer-contact-item {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 12px;
    font-size: 0.9rem;
}

.footer-contact-item .icon {
    font-size: 1.1rem;
}

.footer-bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding: 20px 0;
    text-align: center;
    font-size: 0.85rem;
}

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

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

.footer-links {
    display: flex;
    gap: 20px;
    justify-content: center;
    margin-bottom: 10px;
}

/* ===== Responsive ===== */
@media (max-width: 1024px) {
    .hero h1 {
        font-size: 2.4rem;
    }
    
    .products-grid {
        grid-template-columns: 1fr;
        max-width: 500px;
        margin: 0 auto;
    }
    
    .value-grid {
        grid-template-columns: 1fr 1fr;
    }
    
    .about-grid,
    .product-detail-grid {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    
    .product-detail-grid.reverse {
        direction: ltr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr 1fr;
        gap: 30px;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--white);
        flex-direction: column;
        gap: 0;
        padding: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease;
        box-shadow: var(--shadow-md);
    }

    .nav-menu.active {
        max-height: 400px;
    }

    .nav-menu a {
        width: 100%;
        padding: 15px 20px;
        border-bottom: 1px solid var(--gray-100);
    }

    .nav-menu a::after {
        display: none;
    }

    .hamburger {
        display: flex;
    }
    
    .nav-actions {
        gap: 8px;
    }
    
    .nav-login {
        padding: 6px 16px;
        font-size: 0.85rem;
    }
    
    .lang-switch {
        display: none;
    }
    
    .hero h1 {
        font-size: 1.8rem;
    }
    
    .hero p {
        font-size: 1rem;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: 20px;
    }
    
    .section {
        padding: 50px 0;
    }
    
    .section-header h2 {
        font-size: 1.6rem;
    }
    
    .about-features {
        grid-template-columns: 1fr;
    }
    
    .value-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
    }
    
    .product-detail-visual {
        padding: 30px;
    }
    
    .cta h2 {
        font-size: 1.6rem;
    }
    
    .hero-actions {
        flex-direction: column;
    }
    
    .hero-actions .btn {
        width: 100%;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .hero h1 {
        font-size: 1.5rem;
    }
    
    .nav-logo {
        font-size: 1.1rem;
    }
    
    .nav-logo-icon {
        width: 32px;
        height: 32px;
        font-size: 1rem;
    }
    
    .container {
        padding: 0 16px;
    }
    
    .product-card-header {
        padding: 30px 20px;
    }
    
    .product-card-body {
        padding: 20px;
    }
    
    .about-visual-card {
        padding: 30px 20px;
    }
}

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

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

/* ===== Back to Top ===== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 48px;
    height: 48px;
    background: var(--primary);
    color: var(--white);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    transition: var(--transition);
    opacity: 0;
    visibility: hidden;
    z-index: 999;
    border: none;
}

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

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-3px);
}