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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #f59e0b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --text-dark: #1e293b;
    --text-light: #64748b;
    --bg-light: #f8fafc;
    --bg-white: #ffffff;
    --border-color: #e2e8f0;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --border-radius: 8px;
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* Header */
.header {
    background: var(--bg-white);
    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-dark);
    font-weight: 600;
    font-size: 1.25rem;
}

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

.nav-list a {
    text-decoration: none;
    color: var(--text-light);
    font-weight: 500;
    transition: color 0.2s;
}

.nav-list a:hover,
.nav-list a:focus {
    color: var(--primary-color);
}

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

.mobile-menu-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-dark);
    margin: 2px 0;
    transition: 0.3s;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 500;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s;
    font-size: 1rem;
}

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

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

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

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

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

.btn-outline:hover,
.btn-outline:focus {
    background: var(--bg-light);
}

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

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

.hero h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 1rem;
    line-height: 1.2;
}

.hero p {
    font-size: 1.25rem;
    color: var(--text-light);
    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-white);
}

.features h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    font-weight: 600;
}

.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(--border-radius);
    background: var(--bg-light);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
}

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

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

.featured-courses h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    font-weight: 600;
}

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

.course-card {
    background: var(--bg-white);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
}

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

.course-image {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

.course-content {
    padding: 1.5rem;
}

.course-tag {
    display: inline-block;
    background: var(--accent-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 1rem;
}

.course-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.course-title a {
    text-decoration: none;
    color: var(--text-dark);
}

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

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

.course-description {
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

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

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

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

/* Trust Indicators */
.trust-indicators {
    padding: 4rem 0;
    background: var(--bg-white);
}

.trust-indicators h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    font-weight: 600;
}

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

.trust-item {
    text-align: center;
    padding: 2rem;
}

.trust-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.trust-item h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
}

.trust-item p {
    color: var(--text-light);
}

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

.course-header {
    background: var(--bg-light);
    padding: 3rem 0;
    margin-bottom: 3rem;
}

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

.course-info h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
}

.course-sidebar {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    position: sticky;
    top: 100px;
}

.course-sidebar img {
    width: 100%;
    border-radius: var(--border-radius);
    margin-bottom: 1.5rem;
}

.course-sidebar .course-price {
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.course-sidebar .btn {
    width: 100%;
    margin-bottom: 1rem;
}

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

.course-main {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.course-main h2 {
    font-size: 1.75rem;
    margin-bottom: 1.5rem;
    font-weight: 600;
}

.course-main h3 {
    font-size: 1.5rem;
    margin: 2rem 0 1rem 0;
    font-weight: 600;
}

.course-main ul {
    margin-left: 1.5rem;
    margin-bottom: 1.5rem;
}

.course-main li {
    margin-bottom: 0.5rem;
}

.curriculum-item {
    padding: 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    margin-bottom: 0.5rem;
}

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

.faq-question {
    padding: 1rem;
    background: var(--bg-light);
    cursor: pointer;
    font-weight: 500;
}

.faq-answer {
    padding: 1rem;
    border-top: 1px solid var(--border-color);
    color: var(--text-light);
}

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

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-control {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

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

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

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

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

/* Checkout */
.checkout-header {
    background: var(--bg-light);
    padding: 2rem 0;
    text-align: center;
}

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

.step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    background: var(--bg-white);
}

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

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

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

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

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

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

.summary-total {
    font-size: 1.25rem;
    font-weight: 600;
}

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

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

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

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

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
    font-weight: 600;
}

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

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

.footer-section a {
    color: #cbd5e1;
    text-decoration: none;
}

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

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid #374151;
    color: #9ca3af;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav {
        display: none;
    }
    
    .mobile-menu-toggle {
        display: flex;
    }
    
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .hero-actions {
        justify-content: center;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .course-header .container,
    .course-details,
    .checkout-grid {
        grid-template-columns: 1fr;
    }
    
    .course-sidebar {
        position: static;
    }
    
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .features h2,
    .featured-courses h2,
    .trust-indicators h2 {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 0.75rem;
    }
    
    .hero {
        padding: 2rem 0;
    }
    
    .hero h1 {
        font-size: 1.75rem;
    }
    
    .hero p {
        font-size: 1rem;
    }
    
    .hero-actions {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .btn {
        padding: 0.625rem 1.25rem;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    .course-card {
        margin: 0 0.5rem;
    }
    
    .checkout-steps {
        flex-direction: column;
        align-items: center;
        gap: 1rem;
    }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

.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;
}

/* Focus styles */
.btn:focus,
.form-control:focus,
a:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}