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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #f59e0b;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-accent: #f1f5f9;
    --border-color: #e2e8f0;
    --border-light: #f1f5f9;
    --success-color: #10b981;
    --error-color: #ef4444;
    --warning-color: #f59e0b;
    --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;
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 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: 1200px;
    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: 700;
    font-size: 1.25rem;
}

.nav {
    display: flex;
    gap: 2rem;
}

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.2s;
    position: relative;
}

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -0.5rem;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary-color);
    border-radius: 1px;
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 3px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

.mobile-menu-toggle span {
    width: 20px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 1px;
    transition: all 0.3s;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    text-decoration: none;
    border: 2px solid transparent;
    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-secondary);
    color: var(--text-primary);
    border-color: var(--border-color);
}

.btn-secondary:hover {
    background: var(--bg-accent);
}

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

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

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

.btn-success:hover {
    background: #059669;
}

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

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

.hero-text h1 {
    font-size: 3rem;
    font-weight: 800;
    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-actions {
    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(250px, 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 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

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

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

/* Course Sections */
.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);
}

.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;
}

.course-content {
    padding: 1.5rem;
}

.course-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.course-category {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: var(--accent-color);
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: var(--radius-sm);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.course-price {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
}

.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: 1rem;
    line-height: 1.5;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-bottom: 1rem;
}

.course-actions {
    display: flex;
    gap: 0.75rem;
}

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

/* Section Footer */
.section-footer {
    text-align: center;
}

/* CTA Section */
.cta-section {
    padding: 4rem 0;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-hover) 100%);
    color: white;
}

.cta-content {
    text-align: center;
}

.cta-content h2 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.cta-content p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

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

.cta-content .btn:hover {
    background: var(--bg-accent);
}

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

.page-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

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

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

.controls-grid {
    display: grid;
    grid-template-columns: 1fr auto auto;
    gap: 1rem;
    align-items: center;
}

.search-box {
    position: relative;
}

.search-input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: border-color 0.2s;
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.filter-select,
.sort-select {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--bg-primary);
    cursor: pointer;
}

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

/* Course Detail Page */
.course-detail {
    padding: 2rem 0;
}

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

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

.course-sidebar {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--radius-lg);
    height: fit-content;
    position: sticky;
    top: 100px;
}

.course-detail-image {
    width: 100%;
    height: 300px;
    object-fit: cover;
    border-radius: var(--radius-lg);
    margin-bottom: 2rem;
}

.course-detail-header {
    margin-bottom: 2rem;
}

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

.course-detail-meta {
    display: flex;
    gap: 2rem;
    margin-bottom: 1rem;
    font-size: 0.875rem;
    color: var(--text-muted);
}

.course-detail-description {
    font-size: 1.125rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.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);
}

.course-section ul {
    list-style: none;
    padding-left: 0;
}

.course-section li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-light);
    position: relative;
    padding-left: 1.5rem;
}

.course-section li:before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

.curriculum-item {
    background: var(--bg-secondary);
    padding: 1rem;
    border-radius: var(--radius-md);
    margin-bottom: 0.5rem;
    border: 1px solid var(--border-light);
}

.curriculum-item:before {
    content: '📚';
    margin-right: 0.5rem;
}

.instructor-card {
    background: var(--bg-secondary);
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-light);
}

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

.instructor-bio {
    color: var(--text-secondary);
    line-height: 1.6;
}

.faq-item {
    border-bottom: 1px solid var(--border-light);
    padding: 1rem 0;
}

.faq-question {
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.faq-answer {
    color: var(--text-secondary);
    line-height: 1.6;
}

.purchase-card {
    text-align: center;
}

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

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

.purchase-features li {
    padding: 0.5rem 0;
    color: var(--text-secondary);
    border-bottom: none;
    padding-left: 1.5rem;
}

.purchase-features li:before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

/* Checkout Pages */
.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;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    background: var(--bg-accent);
    color: var(--text-muted);
    font-weight: 600;
}

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

.progress-step.completed {
    background: var(--success-color);
    color: white;
}

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

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

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

.checkout-summary {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--radius-lg);
    height: fit-content;
    position: sticky;
    top: 100px;
}

.form-section {
    margin-bottom: 2rem;
}

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

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

.form-group {
    margin-bottom: 1rem;
}

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

.form-label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

.form-input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: border-color 0.2s;
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

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

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

.form-checkbox {
    display: flex;
    align-items: flex-start;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.form-checkbox input {
    margin-top: 0.25rem;
}

.form-checkbox label {
    font-size: 0.875rem;
    line-height: 1.4;
    color: var(--text-secondary);
}

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

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

.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: 700;
    font-size: 1.25rem;
    color: var(--primary-color);
}

.summary-course {
    margin-bottom: 2rem;
}

.summary-course-title {
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.summary-course-meta {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.trust-indicators {
    margin-top: 2rem;
    text-align: center;
}

.trust-icons {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.trust-icon {
    width: 40px;
    height: 24px;
    background: var(--bg-accent);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.trust-text {
    font-size: 0.875rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.25rem;
}

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

.success-icon {
    width: 80px;
    height: 80px;
    background: var(--success-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 2rem;
    font-size: 2rem;
    color: white;
}

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

.success-message {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 3rem;
}

.order-details {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--radius-lg);
    margin: 2rem auto;
    max-width: 600px;
    text-align: left;
}

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

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

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
    gap: 2rem;
    margin-bottom: 2rem;
}

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

.footer-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 700;
    font-size: 1.25rem;
    margin-bottom: 1rem;
}

.footer-section p {
    color: rgba(255, 255, 255, 0.8);
    line-height: 1.6;
}

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

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

.footer-section a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color 0.2s;
}

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

.contact-info p {
    margin-bottom: 0.5rem;
    color: rgba(255, 255, 255, 0.8);
}

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

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

.footer-legal a {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.875rem;
}

.footer-bottom p {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.875rem;
}

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

.content-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 1rem;
}

.content-page h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 2rem;
    color: var(--text-primary);
}

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

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

.content-page p {
    margin-bottom: 1rem;
    line-height: 1.6;
    color: var(--text-secondary);
}

.content-page ul,
.content-page ol {
    margin-bottom: 1rem;
    padding-left: 1.5rem;
}

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

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

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

/* Contact Form */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    margin-top: 2rem;
}

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

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

.contact-info-section h3 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.contact-detail {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.contact-icon {
    width: 40px;
    height: 40px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.125rem;
}

.contact-detail-content h4 {
    font-weight: 600;
    margin-bottom: 0.25rem;
    color: var(--text-primary);
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .nav {
        display: none;
    }
    
    .mobile-menu-toggle {
        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-grid {
        grid-template-columns: 1fr;
    }
    
    .course-sidebar {
        position: static;
        order: -1;
    }
    
    .checkout-grid {
        grid-template-columns: 1fr;
    }
    
    .checkout-summary {
        position: static;
        order: -1;
    }
    
    .controls-grid {
        grid-template-columns: 1fr;
    }
    
    .hero-actions {
        flex-direction: column;
        align-items: center;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
    }
    
    .footer-bottom {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }
    
    .contact-grid {
        grid-template-columns: 1fr;
    }
    
    .form-grid {
        grid-template-columns: 1fr;
    }
    
    .checkout-progress {
        flex-direction: column;
        align-items: center;
    }
}

@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;
    }
    
    .course-detail-title {
        font-size: 1.75rem;
    }
    
    .page-title {
        font-size: 1.75rem;
    }
    
    .btn {
        padding: 0.625rem 1.25rem;
        font-size: 0.875rem;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    .course-card {
        margin-bottom: 1rem;
    }
}

/* Focus States for Accessibility */
.btn:focus,
.form-input:focus,
.nav-link:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Loading States */
.loading {
    opacity: 0.6;
    pointer-events: none;
}

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    border: 2px solid var(--primary-color);
    border-top: 2px solid transparent;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    transform: translate(-50%, -50%);
}

@keyframes spin {
    0% { transform: translate(-50%, -50%) rotate(0deg); }
    100% { transform: translate(-50%, -50%) rotate(360deg); }
}

/* Print Styles */
@media print {
    .header,
    .footer,
    .btn,
    .checkout-summary {
        display: none;
    }
    
    body {
        font-size: 12pt;
        line-height: 1.4;
    }
    
    .container {
        max-width: none;
        padding: 0;
    }
}