:root {
    --primary-color: #0ea5e9;
    --primary-dark: #0284c7;
    --secondary-color: #06b6d4;
    --accent-color: #f59e0b;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --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);
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
    --transition-slow: 500ms ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    font-size: 16px;
    line-height: 1.7;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    overflow-x: hidden;
}

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

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

ul,
ol {
    list-style: none;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.container-narrow {
    max-width: 800px;
}

header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    transition: all var(--transition-normal);
}

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

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

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.25rem;
}

.nav-desktop {
    display: flex;
    align-items: center;
    gap: 2rem;
}

.nav-desktop a {
    font-weight: 500;
    color: var(--text-secondary);
    padding: 0.5rem 0;
    position: relative;
}

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

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

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

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

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

.nav-mobile {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    right: 0;
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem;
    box-shadow: var(--shadow-lg);
    transform: translateY(-100%);
    opacity: 0;
    transition: all var(--transition-normal);
}

.nav-mobile.active {
    transform: translateY(0);
    top: 100%;
    opacity: 1;
}

.nav-mobile a {
    display: block;
    padding: 0.75rem 1rem;
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.nav-mobile a:hover {
    background: var(--bg-secondary);
    color: var(--primary-color);
}

.hero {
    padding: 140px 0 80px;
    background: linear-gradient(180deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 60%;
    height: 200%;
    background: radial-gradient(circle, rgba(14, 165, 233, 0.08) 0%, transparent 70%);
    animation: float 20s ease-in-out infinite;
}

.hero::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -10%;
    width: 40%;
    height: 150%;
    background: radial-gradient(circle, rgba(6, 182, 212, 0.06) 0%, transparent 70%);
    animation: float 15s ease-in-out infinite reverse;
}

@keyframes float {

    0%,
    100% {
        transform: translateY(0) rotate(0deg);
    }

    50% {
        transform: translateY(-30px) rotate(5deg);
    }
}

.hero-content {
    position: relative;
    z-index: 1;
    text-align: center;
    max-width: 800px;
    margin: 0 auto;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: 50px;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    animation: fadeInUp 0.6s ease;
}

.hero-badge span {
    color: var(--primary-color);
    font-weight: 600;
}

.hero h1 {
    font-size: clamp(2.5rem, 5vw, 3.5rem);
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    animation: fadeInUp 0.6s ease 0.1s backwards;
}

.hero h1 .highlight {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    animation: fadeInUp 0.6s ease 0.2s backwards;
}

.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
    animation: fadeInUp 0.6s ease 0.3s backwards;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.875rem 1.75rem;
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-normal);
    border: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    box-shadow: 0 4px 14px rgba(14, 165, 233, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(14, 165, 233, 0.5);
}

.btn-secondary {
    background: var(--bg-primary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

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

.stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-top: 4rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    animation: fadeInUp 0.6s ease 0.4s backwards;
}

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

.stat-value {
    font-size: 2rem;
    font-weight: 800;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

section {
    padding: 80px 0;
}

.section-header {
    text-align: center;
    max-width: 600px;
    margin: 0 auto 3rem;
}

.section-header h2 {
    font-size: 2.25rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.section-header p {
    color: var(--text-secondary);
    font-size: 1.125rem;
}

.lessons-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.5rem;
}

.lesson-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 1.5rem;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.lesson-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    transform: scaleX(0);
    transform-origin: left;
    transition: transform var(--transition-normal);
}

.lesson-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: transparent;
}

.lesson-card:hover::before {
    transform: scaleX(1);
}

.lesson-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: var(--bg-tertiary);
    color: var(--primary-color);
    font-weight: 700;
    font-size: 0.875rem;
    border-radius: var(--radius-md);
    margin-bottom: 1rem;
}

.lesson-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    transition: color var(--transition-fast);
}

.lesson-card:hover h3 {
    color: var(--primary-color);
}

.lesson-card p {
    color: var(--text-secondary);
    font-size: 0.9375rem;
    margin-bottom: 1rem;
    line-height: 1.6;
}

.lesson-meta {
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: 0.8125rem;
    color: var(--text-light);
}

.lesson-meta span {
    display: flex;
    align-items: center;
    gap: 0.375rem;
}

.features {
    background: var(--bg-secondary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: var(--radius-xl);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.feature-icon {
    width: 64px;
    height: 64px;
    background: linear-gradient(135deg, rgba(14, 165, 233, 0.1), rgba(6, 182, 212, 0.1));
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1.5rem;
    font-size: 1.75rem;
    color: var(--primary-color);
}

.feature-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 0.9375rem;
}

.cta {
    background: linear-gradient(135deg, var(--text-primary) 0%, #334155 100%);
    color: white;
    text-align: center;
}

.cta h2 {
    font-size: 2.25rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.cta p {
    color: var(--text-light);
    font-size: 1.125rem;
    margin-bottom: 2rem;
    max-width: 500px;
    margin-left: auto;
    margin-right: auto;
}

footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 60px 0 30px;
}

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

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

.footer-brand .logo {
    margin-bottom: 1rem;
}

.footer-brand p {
    color: var(--text-secondary);
    font-size: 0.9375rem;
    line-height: 1.7;
}

.footer-links h4 {
    font-size: 0.875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-primary);
    margin-bottom: 1.25rem;
}

.footer-links ul {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.footer-links a {
    color: var(--text-secondary);
    font-size: 0.9375rem;
    transition: color var(--transition-fast);
}

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

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.footer-bottom-links {
    display: flex;
    gap: 1.5rem;
}

.footer-bottom-links a {
    color: var(--text-secondary);
}

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

.article-hero {
    padding: 120px 0 60px;
    background: var(--bg-secondary);
    position: relative;
}

.article-hero::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 100px;
    background: linear-gradient(to top, var(--bg-primary), transparent);
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.breadcrumb a {
    color: var(--text-secondary);
}

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

.breadcrumb .separator {
    color: var(--text-light);
}

.article-hero h1 {
    font-size: clamp(2rem, 4vw, 2.75rem);
    font-weight: 800;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.article-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    font-size: 0.9375rem;
    color: var(--text-secondary);
}

.article-meta span {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.article-content {
    padding: 60px 0;
}

.article-body {
    max-width: 800px;
    margin: 0 auto;
}

.article-body h2 {
    font-size: 1.75rem;
    font-weight: 700;
    margin: 2.5rem 0 1rem;
    color: var(--text-primary);
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}

.article-body h2:first-child {
    margin-top: 0;
    padding-top: 0;
    border-top: none;
}

.article-body h3 {
    font-size: 1.375rem;
    font-weight: 600;
    margin: 2rem 0 0.75rem;
    color: var(--text-primary);
}

.article-body p {
    margin-bottom: 1.25rem;
    color: var(--text-primary);
    line-height: 1.8;
}

.article-body ul,
.article-body ol {
    margin-bottom: 1.25rem;
    padding-left: 1.5rem;
}

.article-body ul {
    list-style: disc;
}

.article-body ol {
    list-style: decimal;
}

.article-body li {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    line-height: 1.7;
}

.article-body strong {
    font-weight: 600;
    color: var(--text-primary);
}

.article-body code {
    background: var(--bg-tertiary);
    padding: 0.125rem 0.375rem;
    border-radius: var(--radius-sm);
    font-family: 'Consolas', monospace;
    font-size: 0.875em;
}

.article-body pre {
    background: var(--text-primary);
    color: #e2e8f0;
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    overflow-x: auto;
    margin-bottom: 1.5rem;
}

.article-body pre code {
    background: none;
    padding: 0;
    color: inherit;
}

.info-box {
    background: linear-gradient(135deg, rgba(14, 165, 233, 0.08), rgba(6, 182, 212, 0.05));
    border-left: 4px solid var(--primary-color);
    padding: 1.25rem 1.5rem;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
    margin: 1.5rem 0;
}

.info-box h4 {
    color: var(--primary-color);
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.info-box p {
    margin-bottom: 0;
    color: var(--text-secondary);
}

.warning-box {
    background: rgba(245, 158, 11, 0.1);
    border-left: 4px solid var(--accent-color);
    padding: 1.25rem 1.5rem;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
    margin: 1.5rem 0;
}

.warning-box h4 {
    color: #b45309;
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.warning-box p {
    margin-bottom: 0;
    color: var(--text-secondary);
}

.article-image {
    margin: 2rem 0;
    border-radius: var(--radius-xl);
    overflow: hidden;
    box-shadow: var(--shadow-lg);
}

.article-image img {
    width: 100%;
}

.article-image figcaption {
    background: var(--bg-secondary);
    padding: 0.75rem 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-align: center;
}

.step-list {
    counter-reset: step-counter;
    margin: 1.5rem 0;
}

.step-item {
    counter-increment: step-counter;
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    padding: 1.25rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
}

.step-item:hover {
    background: var(--bg-tertiary);
    transform: translateX(4px);
}

.step-item::before {
    content: counter(step-counter);
    flex-shrink: 0;
    width: 36px;
    height: 36px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    font-weight: 700;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.step-content h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.step-content p {
    margin-bottom: 0;
    color: var(--text-secondary);
}

.summary-box {
    background: var(--bg-secondary);
    border-radius: var(--radius-xl);
    padding: 2rem;
    margin-top: 2rem;
}

.summary-box h3 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.summary-box ul {
    list-style: none;
    padding-left: 0;
}

.summary-box li {
    position: relative;
    padding-left: 1.5rem;
    margin-bottom: 0.75rem;
}

.summary-box li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.5rem;
    width: 8px;
    height: 8px;
    background: var(--primary-color);
    border-radius: 50%;
}

.article-nav {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
}

.nav-link {
    display: flex;
    flex-direction: column;
    padding: 1.5rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
}

.nav-link:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
}

.nav-link.next {
    text-align: right;
}

.nav-label {
    font-size: 0.8125rem;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.5rem;
}

.nav-title {
    font-weight: 600;
    color: var(--text-primary);
}

.legal-content {
    padding: 120px 0 60px;
}

.legal-content h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.legal-content .last-updated {
    color: var(--text-secondary);
    margin-bottom: 3rem;
    font-size: 0.9375rem;
}

.legal-content h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin: 2.5rem 0 1rem;
    color: var(--text-primary);
}

.legal-content h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 2rem 0 0.75rem;
    color: var(--text-primary);
}

.legal-content p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    line-height: 1.8;
}

.legal-content ul {
    list-style: disc;
    padding-left: 1.5rem;
    margin-bottom: 1rem;
}

.legal-content li {
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

.legal-content a {
    color: var(--primary-color);
}

.legal-content a:hover {
    text-decoration: underline;
}

.contact-form {
    max-width: 600px;
    margin: 2rem 0;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    font-weight: 500;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.875rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-family: inherit;
    transition: all var(--transition-fast);
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(14, 165, 233, 0.1);
}

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

@media (max-width: 1024px) {
    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .footer-brand {
        grid-column: span 2;
        max-width: none;
    }
}

@media (max-width: 768px) {
    .nav-desktop {
        display: none;
    }

    .nav-toggle {
        display: flex;
    }

    .nav-mobile {
        display: block;
    }

    .hero {
        padding: 120px 0 60px;
    }

    .stats {
        flex-direction: column;
        gap: 1.5rem;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .footer-brand {
        grid-column: auto;
    }

    .footer-bottom {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }

    .article-nav {
        grid-template-columns: 1fr;
    }

    .nav-link.next {
        text-align: left;
    }
}

@media (max-width: 480px) {
    .hero-buttons {
        flex-direction: column;
        width: 100%;
    }

    .btn {
        width: 100%;
        justify-content: center;
    }

    .lessons-grid {
        grid-template-columns: 1fr;
    }

    .article-meta {
        flex-direction: column;
        gap: 0.5rem;
    }
}

.scroll-reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.6s ease;
}

.scroll-reveal.revealed {
    opacity: 1;
    transform: translateY(0);
}

.progress-bar {
    position: fixed;
    top: 70px;
    left: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    z-index: 999;
    transition: width 0.1s ease;
}

.toc {
    position: sticky;
    top: 100px;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
}

.toc h4 {
    font-size: 0.875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.toc ul {
    list-style: none;
}

.toc li {
    margin-bottom: 0.5rem;
}

.toc a {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    display: block;
    padding: 0.375rem 0;
    border-left: 2px solid transparent;
    padding-left: 1rem;
    transition: all var(--transition-fast);
}

.toc a:hover,
.toc a.active {
    color: var(--primary-color);
    border-left-color: var(--primary-color);
}

.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 48px;
    height: 48px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition-normal);
    z-index: 100;
}

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

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-4px);
}