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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #f59e0b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --border-light: #f1f5f9;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --max-width: 1200px;
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
}

.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1rem;
}

/* Header */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 600;
    font-size: 1.25rem;
}

.nav-list {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.2s;
    padding: 0.5rem 0;
}

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

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    gap: 0.25rem;
}

.mobile-menu-btn span {
    width: 1.5rem;
    height: 0.125rem;
    background: var(--text-primary);
    transition: all 0.2s;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-md);
    font-weight: 500;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.2s;
    font-size: 0.875rem;
    line-height: 1.25rem;
}

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

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

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

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

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

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

/* Hero Section */
.hero {
    padding: 4rem 0;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
}

.hero-text h1 {
    font-size: 3rem;
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.hero-text p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
}

.hero-image img {
    width: 100%;
    height: auto;
}

/* Features Section */
.features {
    padding: 4rem 0;
    background: var(--bg-primary);
}

.features h2 {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 3rem;
    color: var(--text-primary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    text-align: center;
    padding: 2rem;
    border-radius: var(--radius-lg);
    background: var(--bg-secondary);
    border: 1px solid var(--border-light);
}

.feature-icon {
    width: 4rem;
    height: 4rem;
    margin: 0 auto 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
}

.feature-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

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

/* Featured Courses Section */
.featured-courses {
    padding: 4rem 0;
    background: var(--bg-secondary);
}

.section-header {
    text-align: center;
    margin-bottom: 3rem;
}

.section-header h2 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.section-header p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.course-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: transform 0.2s, box-shadow 0.2s;
    border: 1px solid var(--border-light);
}

.course-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.course-image {
    width: 100%;
    height: 200px;
    object-fit: cover;
    background: var(--bg-tertiary);
}

.course-content {
    padding: 1.5rem;
}

.course-meta {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.course-category {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 500;
}

.course-difficulty {
    color: var(--text-light);
    font-size: 0.875rem;
}

.course-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.course-title a {
    text-decoration: none;
    color: inherit;
}

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

.course-description {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    font-size: 0.875rem;
}

.course-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.course-price {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.course-duration {
    color: var(--text-light);
    font-size: 0.875rem;
}

.section-footer {
    text-align: center;
}

/* Trust Section */
.trust-section {
    padding: 3rem 0;
    background: var(--bg-primary);
}

.trust-section h2 {
    text-align: center;
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 2rem;
    color: var(--text-primary);
}

.trust-features {
    display: flex;
    justify-content: center;
    gap: 3rem;
    flex-wrap: wrap;
}

.trust-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.trust-item svg {
    color: var(--success-color);
}

/* Course Catalog */
.catalog-header {
    padding: 2rem 0;
    background: var(--bg-secondary);
}

.catalog-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.catalog-subtitle {
    font-size: 1.125rem;
    color: var(--text-secondary);
}

.catalog-filters {
    padding: 2rem 0;
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
}

.filters-row {
    display: flex;
    gap: 1rem;
    align-items: center;
    flex-wrap: wrap;
}

.filter-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.filter-group label {
    font-weight: 500;
    color: var(--text-primary);
}

.filter-input {
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    background: var(--bg-primary);
}

.filter-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgb(37 99 235 / 0.1);
}

.catalog-content {
    padding: 2rem 0;
}

/* Course Detail */
.course-detail-header {
    padding: 2rem 0;
    background: var(--bg-secondary);
}

.course-detail-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 3rem;
    align-items: start;
}

.course-detail-main h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.course-detail-meta {
    display: flex;
    gap: 2rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
}

.course-detail-sidebar {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    position: sticky;
    top: 2rem;
}

.sidebar-price {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.sidebar-features {
    list-style: none;
    margin-bottom: 2rem;
}

.sidebar-features li {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 0;
    color: var(--text-secondary);
}

.sidebar-features svg {
    color: var(--success-color);
    flex-shrink: 0;
}

.course-sections {
    padding: 2rem 0;
}

.course-section {
    margin-bottom: 3rem;
}

.course-section h2 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.course-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.learning-objectives {
    list-style: none;
}

.learning-objectives li {
    display: flex;
    align-items: flex-start;
    gap: 0.5rem;
    padding: 0.5rem 0;
    color: var(--text-secondary);
}

.learning-objectives svg {
    color: var(--success-color);
    flex-shrink: 0;
    margin-top: 0.125rem;
}

.curriculum-list {
    list-style: none;
}

.curriculum-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: 0.5rem;
    background: var(--bg-secondary);
}

.lesson-number {
    background: var(--primary-color);
    color: white;
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.875rem;
    font-weight: 600;
    flex-shrink: 0;
}

.instructor-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
}

.instructor-name {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.faq-list {
    list-style: none;
}

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: 1rem;
    overflow: hidden;
}

.faq-question {
    background: var(--bg-secondary);
    padding: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    cursor: pointer;
    border: none;
    width: 100%;
    text-align: left;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.faq-question:hover {
    background: var(--bg-tertiary);
}

.faq-answer {
    padding: 1rem;
    color: var(--text-secondary);
    display: none;
}

.faq-answer.active {
    display: block;
}

/* Checkout */
.checkout-header {
    padding: 2rem 0;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.checkout-progress {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 2rem;
}

.progress-step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-light);
}

.progress-step.active {
    color: var(--primary-color);
}

.step-number {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    background: var(--bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    border: 2px solid var(--border-color);
}

.progress-step.active .step-number {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.checkout-content {
    padding: 2rem 0;
}

.checkout-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 3rem;
}

.form-section {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    margin-bottom: 2rem;
}

.form-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.form-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

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

.form-group.full-width {
    grid-column: 1 / -1;
}

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

.form-input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--bg-primary);
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgb(37 99 235 / 0.1);
}

.form-input.error {
    border-color: var(--danger-color);
}

.error-message {
    color: var(--danger-color);
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

.checkout-summary {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    position: sticky;
    top: 2rem;
}

.summary-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.summary-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-light);
}

.summary-item:last-child {
    border-bottom: none;
    font-weight: 600;
    font-size: 1.125rem;
}

.payment-icons {
    display: flex;
    gap: 0.5rem;
    margin: 1rem 0;
    align-items: center;
}

.payment-icon {
    width: 2rem;
    height: 1.5rem;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.security-notice {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-top: 1rem;
}

.security-notice svg {
    color: var(--success-color);
}

.checkbox-group {
    display: flex;
    align-items: flex-start;
    gap: 0.5rem;
    margin: 1.5rem 0;
}

.checkbox-group input {
    margin-top: 0.125rem;
}

.checkbox-group label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    cursor: pointer;
}

.checkbox-group a {
    color: var(--primary-color);
    text-decoration: none;
}

.checkbox-group a:hover {
    text-decoration: underline;
}

/* Success Page */
.success-content {
    padding: 4rem 0;
    text-align: center;
}

.success-icon {
    width: 4rem;
    height: 4rem;
    margin: 0 auto 2rem;
    background: var(--success-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.success-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.success-message {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 3rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.order-details {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    margin: 2rem auto;
    max-width: 500px;
    text-align: left;
}

.order-details h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    text-align: center;
}

/* Contact Page */
.contact-content {
    padding: 2rem 0;
}

.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
}

.contact-info {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 2rem;
}

.contact-info h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.contact-item svg {
    color: var(--primary-color);
    flex-shrink: 0;
}

.contact-form {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
}

.contact-form h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.form-textarea {
    width: 100%;
    min-height: 120px;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-family: inherit;
    background: var(--bg-primary);
    resize: vertical;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgb(37 99 235 / 0.1);
}

/* Content Pages */
.content-page {
    padding: 2rem 0;
}

.content-header {
    padding: 2rem 0;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.content-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.content-body {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 0;
}

.content-body h2 {
    font-size: 1.75rem;
    font-weight: 600;
    margin: 2rem 0 1rem;
    color: var(--text-primary);
}

.content-body h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 1.5rem 0 0.75rem;
    color: var(--text-primary);
}

.content-body p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

.content-body ul,
.content-body ol {
    margin-bottom: 1rem;
    padding-left: 2rem;
}

.content-body li {
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.content-body a {
    color: var(--primary-color);
    text-decoration: none;
}

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

/* Footer */
.footer {
    background: var(--text-primary);
    color: var(--bg-primary);
    padding: 3rem 0 1rem;
    margin-top: 4rem;
}

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

.footer-section h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.footer-section ul {
    list-style: none;
}

.footer-section li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: var(--text-light);
    text-decoration: none;
    transition: color 0.2s;
}

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

.footer-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
    font-size: 1.25rem;
}

.footer-section p {
    color: var(--text-light);
    line-height: 1.6;
    margin-bottom: 1rem;
}

.contact-info p {
    margin-bottom: 0.5rem;
}

.contact-info a {
    color: var(--text-light);
    text-decoration: none;
}

.contact-info a:hover {
    color: var(--bg-primary);
}

.footer-bottom {
    border-top: 1px solid var(--secondary-color);
    padding-top: 1rem;
    text-align: center;
    color: var(--text-light);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav {
        display: none;
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-text h1 {
        font-size: 2rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .course-detail-content {
        grid-template-columns: 1fr;
    }
    
    .checkout-grid {
        grid-template-columns: 1fr;
    }
    
    .contact-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
    }
    
    .form-grid {
        grid-template-columns: 1fr;
    }
    
    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .trust-features {
        flex-direction: column;
        align-items: center;
        gap: 1.5rem;
    }
    
    .filters-row {
        flex-direction: column;
        align-items: stretch;
        gap: 1rem;
    }
    
    .checkout-progress {
        flex-direction: column;
        align-items: center;
        gap: 1rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 0.75rem;
    }
    
    .hero {
        padding: 2rem 0;
    }
    
    .hero-text h1 {
        font-size: 1.75rem;
    }
    
    .hero-text p {
        font-size: 1rem;
    }
    
    .features {
        padding: 2rem 0;
    }
    
    .features h2 {
        font-size: 2rem;
    }
    
    .featured-courses {
        padding: 2rem 0;
    }
    
    .section-header h2 {
        font-size: 2rem;
    }
    
    .course-card {
        margin: 0 0.5rem;
    }
    
    .form-section,
    .checkout-summary {
        padding: 1rem;
    }
}

/* Print Styles */
@media print {
    .header,
    .footer,
    .btn,
    .mobile-menu-btn {
        display: none;
    }
    
    body {
        font-size: 12pt;
        line-height: 1.4;
    }
    
    .container {
        max-width: none;
        padding: 0;
    }
    
    .course-card,
    .feature-card {
        break-inside: avoid;
    }
}

/* Focus Styles for Accessibility */
button:focus,
input:focus,
select:focus,
textarea:focus,
a:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
    
    html {
        scroll-behavior: auto;
    }
}