:root {
    --primary: #0066cc;
    --primary-dark: #0052a3;
    --primary-light: rgba(0, 102, 204, 0.1);
    --accent: #00a1ff;
    --secondary: #6c757d;
    
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-card: #ffffff;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --text-muted: #868e96;
    
    --shadow-light: 0 2px 12px rgba(0, 0, 0, 0.08);
    --shadow-medium: 0 4px 20px rgba(0, 0, 0, 0.12);
    --border-color: #e9ecef;
    --border-radius: 8px;
    --border-radius-lg: 12px;
    
    --font-primary: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', Monaco, Consolas, 'Liberation Mono', 'Courier New', monospace;
    
    --transition: all 0.3s ease;
}

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

body {
    font-family: var(--font-primary);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    font-size: 16px;
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.skip-link {
    position: absolute;
    top: -40px;
    left: 6px;
    background: var(--primary);
    color: white;
    padding: 8px;
    text-decoration: none;
    border-radius: 4px;
    z-index: 1001;
    transition: var(--transition);
}

.skip-link:focus {
    top: 6px;
}

.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    transition: var(--transition);
}

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

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--text-primary);
    z-index: 1001;
}

.logo-image {
    height: 32px;
    width: auto;
}

.logo-text {
    font-size: 20px;
    font-weight: 600;
    color: var(--primary);
}

.nav {
    display: flex;
    align-items: center;
    gap: 32px;
    position: relative;
    z-index: 1001;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

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

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary);
    transition: var(--transition);
}

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

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 8px;
    z-index: 1001;
}

.hamburger-line {
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    margin: 3px 0;
    transition: var(--transition);
    border-radius: 2px;
}

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

.mobile-menu-toggle.active .hamburger-line:nth-child(2) {
    opacity: 0;
}

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

.mobile-menu-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100vh;
    background: rgba(0, 0, 0, 0.5);
    z-index: 999;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
}

.mobile-menu-overlay.active {
    opacity: 1;
    visibility: visible;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    border: none;
    border-radius: var(--border-radius);
    font-weight: 500;
    font-family: inherit;
    text-decoration: none;
    transition: var(--transition);
    cursor: pointer;
    font-size: 14px;
}

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

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

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

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

.hero {
    padding: 120px 0 80px;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
}

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

.hero-text h1 {
    font-size: 3.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 12px;
}

.hero-subtitle {
    font-size: 1.4rem;
    color: var(--primary);
    font-weight: 500;
    margin-bottom: 24px;
}

.description {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 32px;
    line-height: 1.7;
}

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

.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.code-demo {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-medium);
    max-width: 400px;
    width: 100%;
}

.code-header {
    background: var(--bg-secondary);
    padding: 12px 16px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
}

.code-controls {
    display: flex;
    gap: 6px;
}

.control {
    width: 12px;
    height: 12px;
    border-radius: 50%;
}

.control.red { background: #ff5f56; }
.control.yellow { background: #ffbd2e; }
.control.green { background: #27ca3f; }

.file-name {
    font-family: var(--font-mono);
    font-size: 12px;
    color: var(--text-secondary);
}

.code-content {
    padding: 20px;
    font-family: var(--font-mono);
    background: #f8f9fa;
}

.line {
    display: flex;
    align-items: center;
    margin-bottom: 8px;
    font-size: 14px;
}

.line-num {
    color: var(--text-muted);
    margin-right: 16px;
    width: 20px;
    text-align: right;
}

.code {
    color: var(--text-primary);
}

.about, .features, .examples, .pricing, .contact {
    padding: 80px 0;
}

.about {
    background: var(--bg-primary);
}

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

.examples {
    background: var(--bg-primary);
}

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

.contact {
    background: var(--bg-primary);
}

.section-header {
    text-align: center;
    margin-bottom: 60px;
}

.section-header h2 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 16px;
}

.section-header p {
    font-size: 1.2rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
}

.about-text p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 40px;
    line-height: 1.7;
}

.features-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 32px;
}

.feature-item h4 {
    color: var(--primary);
    font-weight: 600;
    margin-bottom: 8px;
}

.feature-item p {
    color: var(--text-secondary);
    line-height: 1.6;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 32px;
}

.feature-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 32px;
    transition: var(--transition);
    opacity: 0;
    transform: translateY(20px);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-medium);
    border-color: var(--primary);
}

.feature-icon {
    width: 64px;
    height: 64px;
    background: var(--primary-light);
    border-radius: var(--border-radius);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
}

.icon-syntax, .icon-practice, .icon-visualization, .icon-education {
    width: 32px;
    height: 32px;
    background: var(--primary);
    border-radius: 4px;
}

.feature-card h3 {
    color: var(--text-primary);
    font-weight: 600;
    margin-bottom: 12px;
    font-size: 1.2rem;
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 32px;
}

.example-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 24px;
    transition: var(--transition);
    opacity: 0;
    transform: translateY(20px);
}

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

.example-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.example-header h4 {
    color: var(--text-primary);
    font-weight: 600;
    font-size: 1.1rem;
}

.difficulty {
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.difficulty.easy {
    background: rgba(40, 167, 69, 0.1);
    color: #28a745;
}

.difficulty.medium {
    background: rgba(255, 193, 7, 0.1);
    color: #ffc107;
}

.difficulty.hard {
    background: rgba(220, 53, 69, 0.1);
    color: #dc3545;
}

.code-block {
    background: #f8f9fa;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 16px;
    font-family: var(--font-mono);
    font-size: 14px;
    overflow-x: auto;
}

.code-block .line {
    color: var(--text-primary);
    margin-bottom: 6px;
    white-space: pre;
}

.code-block .line:last-child {
    margin-bottom: 0;
}

.pricing-content {
    max-width: 1000px;
    margin: 0 auto;
}

.pricing-info {
    display: grid;
    grid-template-columns: 400px 1fr;
    gap: 60px;
    align-items: start;
}

.price-card {
    background: var(--bg-card);
    border: 2px solid var(--primary);
    border-radius: var(--border-radius-lg);
    padding: 32px;
    text-align: center;
}

.price-header h3 {
    color: var(--text-primary);
    font-weight: 700;
    margin-bottom: 20px;
}

.price {
    margin-bottom: 24px;
}

.amount {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary);
}

.currency {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-left: 8px;
}

.period {
    display: block;
    color: var(--text-secondary);
    margin-top: 4px;
}

.price-note {
    text-align: center;
    margin-bottom: 24px;
    padding: 12px;
    background: var(--bg-secondary);
    border-radius: var(--border-radius);
}

.price-note p {
    color: var(--text-secondary);
    font-size: 14px;
    margin: 0;
}

.price-features {
    text-align: left;
}

.feature {
    padding: 12px 0;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    position: relative;
    padding-left: 24px;
}

.feature::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--primary);
    font-weight: bold;
}

.feature:last-child {
    border-bottom: none;
}

.process-info h3 {
    color: var(--text-primary);
    font-weight: 700;
    margin-bottom: 32px;
    font-size: 1.5rem;
}

.process-steps {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.step {
    display: flex;
    gap: 20px;
    align-items: flex-start;
}

.step-number {
    width: 40px;
    height: 40px;
    background: var(--primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
}

.step-content h4 {
    color: var(--text-primary);
    font-weight: 600;
    margin-bottom: 8px;
}

.step-content p {
    color: var(--text-secondary);
    line-height: 1.6;
}

.contact-content {
    max-width: 600px;
    margin: 0 auto;
}

.contact-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 32px;
}

.contact-item {
    text-align: center;
    padding: 32px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    opacity: 0;
    transform: translateY(20px);
    transition: var(--transition);
}

.contact-item h4 {
    color: var(--text-primary);
    font-weight: 600;
    margin-bottom: 12px;
}

.contact-item p {
    color: var(--text-secondary);
    margin-bottom: 20px;
}

.contact-link {
    color: var(--primary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

.contact-link:hover {
    color: var(--primary-dark);
    text-decoration: underline;
}

.footer {
    background: var(--text-primary);
    color: white;
    padding: 60px 0 20px;
}

.footer-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    margin-bottom: 40px;
}

.footer-company h4 {
    font-weight: 700;
    margin-bottom: 12px;
}

.footer-company p {
    opacity: 0.8;
    margin-bottom: 20px;
}

.company-details {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.detail {
    color: rgba(255, 255, 255, 0.7);
    font-size: 14px;
}

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

.footer-column h5 {
    font-weight: 600;
    margin-bottom: 16px;
    color: white;
}

.footer-column a {
    display: block;
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    margin-bottom: 8px;
    transition: var(--transition);
}

.footer-column a:hover {
    color: white;
}

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

.footer-bottom p {
    color: rgba(255, 255, 255, 0.7);
    font-size: 14px;
}

@media (max-width: 1024px) {
    .pricing-info {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    
    .nav {
        gap: 24px;
    }
    
    .hero-text h1 {
        font-size: 3rem;
    }
}

@media (max-width: 768px) {
    .container {
        padding: 0 15px;
    }
    
    .hero {
        padding: 100px 0 60px;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        gap: 40px;
        text-align: center;
    }
    
    .hero-visual {
        order: -1;
    }
    
    .hero-text h1 {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.2rem;
    }
    
    .nav {
        position: fixed;
        top: 0;
        left: -100%;
        width: 70%;
        height: 100vh;
        background: var(--bg-primary);
        flex-direction: column;
        justify-content: flex-start;
        align-items: stretch;
        padding-top: 80px;
        padding-left: 0;
        padding-right: 0;
        box-shadow: var(--shadow-medium);
        transition: left 0.3s ease;
        z-index: 1000;
        gap: 0;
    }
    
    .nav.active {
        left: 0;
    }
    
    .nav-link {
        padding: 16px 24px;
        border-bottom: 1px solid var(--border-color);
        display: block;
        color: var(--text-primary);
    }
    
    .nav-link::after {
        display: none;
    }
    
    .nav #loginButton {
        margin: 16px 24px;
        justify-content: center;
    }
    
    .mobile-menu-toggle {
        display: flex;
    }
    
    .features-grid,
    .examples-grid {
        grid-template-columns: 1fr;
        gap: 24px;
    }
    
    .contact-info {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 40px;
    }
    
    .footer-links {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .section-header h2 {
        font-size: 2rem;
    }
    
    .about, .features, .examples, .pricing, .contact {
        padding: 60px 0;
    }
    
    .feature-card,
    .example-card {
        padding: 24px;
    }
    
    .example-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
    }
}

@media (max-width: 480px) {
    .hero-text h1 {
        font-size: 2rem;
    }
    
    .hero-buttons {
        flex-direction: column;
        align-items: center;
        width: 100%;
    }
    
    .btn {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }
    
    .code-demo {
        max-width: 100%;
        margin: 0 auto;
    }
    
    .code-content,
    .code-block {
        font-size: 12px;
        padding: 12px;
    }
    
    .section-header h2 {
        font-size: 1.8rem;
    }
    
    .pricing-info {
        gap: 30px;
    }
    
    .process-steps {
        gap: 20px;
    }
    
    .step {
        flex-direction: column;
        text-align: center;
        gap: 12px;
    }
    
    .nav {
        width: 80%;
    }
    
    .price-card {
        padding: 24px;
    }
    
    .amount {
        font-size: 2.5rem;
    }
    
    .features-list {
        grid-template-columns: 1fr;
        gap: 24px;
    }
}