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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #059669;
    --warning-color: #d97706;
    --error-color: #dc2626;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #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);
    --border-radius: 8px;
    --border-radius-lg: 12px;
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
}

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

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem;
    max-width: 1200px;
    margin: 0 auto;
}

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

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    margin: 0;
    padding: 0;
}

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

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

.nav-toggle span {
    width: 24px;
    height: 3px;
    background: var(--text-primary);
    margin: 2px 0;
    transition: 0.3s;
    border-radius: 2px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.2s ease;
    border: 1px solid transparent;
    cursor: pointer;
    font-size: 1rem;
    line-height: 1.5;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

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

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

.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: #047857;
}

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

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.hero-content h1 {
    font-size: 3rem;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

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

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

.hero-image img {
    width: 100%;
    height: auto;
    max-width: 500px;
}

/* Sections */
.features,
.featured-courses,
.trust-indicators {
    padding: 4rem 0;
}

.features {
    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;
}

.section-footer {
    text-align: center;
    margin-top: 3rem;
}

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

.feature-card,
.trust-item {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
    text-align: center;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.feature-card:hover,
.trust-item:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.feature-icon,
.trust-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    display: block;
}

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

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

/* Course Cards */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

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

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

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

.course-content {
    padding: 1.5rem;
}

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

.course-tag {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.75rem;
    font-weight: 500;
}

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

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

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

.course-desc {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.6;
}

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

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

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

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

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

.course-main {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

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

.course-info {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
}

.course-info h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

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

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

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

.course-info li:last-child {
    border-bottom: none;
}

.curriculum-item {
    background: var(--bg-secondary);
    padding: 1rem 1.5rem;
    border-radius: var(--border-radius);
    margin-bottom: 0.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.lesson-title {
    font-weight: 500;
    color: var(--text-primary);
}

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

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

.instructor-avatar {
    width: 60px;
    height: 60px;
    background: var(--primary-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 600;
    font-size: 1.5rem;
}

.instructor-details h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
    color: var(--text-primary);
}

.instructor-title {
    color: var(--text-muted);
    font-size: 0.875rem;
}

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

.faq-question {
    background: var(--bg-secondary);
    padding: 1rem 1.5rem;
    cursor: pointer;
    font-weight: 500;
    color: var(--text-primary);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

.faq-answer {
    padding: 1rem 1.5rem;
    color: var(--text-secondary);
    line-height: 1.6;
    display: none;
}

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

.faq-toggle {
    transition: transform 0.2s ease;
}

.faq-toggle.active {
    transform: rotate(180deg);
}

/* Courses Page */
.courses-header {
    background: var(--bg-secondary);
    padding: 3rem 0;
    text-align: center;
}

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

.courses-filters {
    background: var(--bg-primary);
    padding: 2rem 0;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 73px;
    z-index: 50;
}

.filters-container {
    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-group select,
.filter-group input {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 0.875rem;
}

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

.courses-content {
    padding: 3rem 0;
}

.courses-results {
    margin-bottom: 2rem;
    color: var(--text-secondary);
}

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

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

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

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group textarea {
    min-height: 120px;
    resize: vertical;
}

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

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

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

.checkbox-group input[type="checkbox"] {
    width: auto;
    margin-top: 0.25rem;
}

.checkbox-group label {
    margin-bottom: 0;
    line-height: 1.5;
}

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

.checkout-steps {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 1rem;
}

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

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

.step-number {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--bg-tertiary);
    color: var(--text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.875rem;
}

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

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

.checkout-content {
    padding: 3rem 0;
}

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

.checkout-form {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
}

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

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

.summary-item:last-child {
    border-bottom: none;
    font-weight: 600;
    font-size: 1.125rem;
    color: var(--text-primary);
}

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

.payment-icon {
    width: 40px;
    height: 24px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
}

.security-info {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-top: 1rem;
    padding: 1rem;
    background: var(--bg-primary);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
}

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

/* Order Success */
.success-message {
    text-align: center;
    padding: 3rem 0;
}

.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;
    color: white;
    font-size: 2rem;
}

.success-message h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.order-details {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--border-radius-lg);
    margin: 2rem 0;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* Static Pages */
.page-header {
    background: var(--bg-secondary);
    padding: 3rem 0;
    text-align: center;
}

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

.page-content {
    padding: 3rem 0;
    max-width: 800px;
    margin: 0 auto;
}

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

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

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

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

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

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

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

.contact-item {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    margin-bottom: 2rem;
}

.contact-icon {
    width: 40px;
    height: 40px;
    background: var(--primary-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.25rem;
    flex-shrink: 0;
}

.contact-details h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

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

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

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

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

.footer-section h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--bg-primary);
}

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

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

.footer-section ul li a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.2s ease;
}

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

.footer-section p {
    color: var(--text-muted);
    line-height: 1.6;
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: var(--text-muted);
    text-decoration: none;
}

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

.footer-bottom {
    border-top: 1px solid var(--secondary-color);
    padding-top: 2rem;
    text-align: center;
    color: var(--text-muted);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 73px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 73px);
        background: var(--bg-primary);
        flex-direction: column;
        align-items: center;
        justify-content: flex-start;
        padding: 2rem 0;
        transition: left 0.3s ease;
        border-top: 1px solid var(--border-color);
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-toggle {
        display: flex;
    }

    .hero .container {
        grid-template-columns: 1fr;
        gap: 2rem;
        text-align: center;
    }

    .hero-content h1 {
        font-size: 2rem;
    }

    .hero-actions {
        justify-content: center;
    }

    .features-grid,
    .trust-grid {
        grid-template-columns: 1fr;
    }

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

    .course-detail-grid {
        grid-template-columns: 1fr;
    }

    .course-sidebar {
        position: static;
        order: -1;
    }

    .filters-container {
        flex-direction: column;
        align-items: stretch;
    }

    .filter-group {
        flex-direction: column;
        align-items: stretch;
    }

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

    .checkout-summary {
        position: static;
        order: -1;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

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

    .page-header h1 {
        font-size: 2rem;
    }

    .section-header h2 {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 0.75rem;
    }

    .hero {
        padding: 2rem 0;
    }

    .hero-content h1 {
        font-size: 1.75rem;
    }

    .hero-actions {
        flex-direction: column;
        align-items: stretch;
    }

    .features,
    .featured-courses,
    .trust-indicators {
        padding: 2rem 0;
    }

    .checkout-steps {
        flex-direction: column;
        gap: 1rem;
    }

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

    .course-card {
        min-width: auto;
    }
}

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

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Loading and Error States */
.loading {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    color: var(--text-muted);
}

.error {
    background: #fef2f2;
    border: 1px solid #fecaca;
    color: var(--error-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin: 1rem 0;
}

.success {
    background: #f0fdf4;
    border: 1px solid #bbf7d0;
    color: var(--success-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin: 1rem 0;
}

/* Animation */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.fade-in {
    animation: fadeIn 0.6s ease-out;
}