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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #ffffff;
}

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

/* Header */
.header {
    background: #fff;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
}

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

.logo a {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: #333;
    font-weight: bold;
    font-size: 1.25rem;
}

.logo img {
    margin-right: 0.5rem;
}

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

.nav a {
    text-decoration: none;
    color: #666;
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav a:hover,
.nav a.active {
    color: #6366f1;
}

.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 600;
    text-align: center;
    transition: all 0.3s ease;
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: #6366f1;
    color: white;
}

.btn-primary:hover {
    background: #5856eb;
    transform: translateY(-1px);
}

.btn-secondary {
    background: transparent;
    color: #6366f1;
    border: 2px solid #6366f1;
}

.btn-secondary:hover {
    background: #6366f1;
    color: white;
}

.btn-outline {
    background: transparent;
    color: #666;
    border: 2px solid #ddd;
}

.btn-outline:hover {
    background: #f8f9fa;
    border-color: #6366f1;
    color: #6366f1;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 0;
    min-height: 70vh;
    display: flex;
    align-items: center;
}

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

.hero h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    line-height: 1.2;
}

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

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

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

/* Features Section */
.features {
    padding: 5rem 0;
    background: #f8f9fa;
}

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

.features-header h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: #333;
}

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

.feature-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    transition: transform 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
}

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

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: #333;
}

/* Course Sections */
.featured-courses,
.courses-catalog {
    padding: 5rem 0;
}

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

.section-header h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: #333;
}

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

.course-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

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

.course-content {
    padding: 1.5rem;
}

.course-meta {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
    font-size: 0.875rem;
    color: #666;
}

.course-tag {
    background: #e0e7ff;
    color: #6366f1;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
}

.course-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: #333;
}

.course-description {
    color: #666;
    margin-bottom: 1rem;
    line-height: 1.5;
}

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

.course-price {
    font-size: 1.5rem;
    font-weight: 700;
    color: #6366f1;
}

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

.course-header {
    background: #f8f9fa;
    padding: 3rem 0;
    margin-bottom: 3rem;
}

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

.course-main h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: #333;
}

.course-sidebar {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    height: fit-content;
    position: sticky;
    top: 100px;
}

.price-section {
    text-align: center;
    margin-bottom: 2rem;
}

.current-price {
    font-size: 2.5rem;
    font-weight: 700;
    color: #6366f1;
}

.course-details-list {
    list-style: none;
    margin-bottom: 2rem;
}

.course-details-list li {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid #eee;
}

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

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: #333;
}

.form-control {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid #ddd;
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.form-control:focus {
    outline: none;
    border-color: #6366f1;
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

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

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

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

/* Checkout */
.checkout-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 0;
}

.checkout-steps {
    display: flex;
    justify-content: center;
    margin-bottom: 3rem;
}

.step {
    display: flex;
    align-items: center;
    padding: 1rem 2rem;
    background: #f8f9fa;
    border-radius: 6px;
    margin: 0 0.5rem;
}

.step.active {
    background: #6366f1;
    color: white;
}

.checkout-form {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.order-summary {
    background: #f8f9fa;
    padding: 2rem;
    border-radius: 12px;
    margin-bottom: 2rem;
}

.payment-methods {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin: 2rem 0;
}

.payment-icon {
    width: 40px;
    height: 24px;
}

/* Filters */
.filters {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    margin-bottom: 2rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.filters-row {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr auto;
    gap: 1rem;
    align-items: end;
}

.filter-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: #333;
}

/* Footer */
.footer {
    background: #1f2937;
    color: white;
    padding: 3rem 0 1rem;
}

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

.footer-section h4 {
    margin-bottom: 1rem;
    color: #f9fafb;
}

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

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

.footer-section a {
    color: #d1d5db;
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-section a:hover {
    color: #6366f1;
}

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

.footer-logo img {
    margin-right: 0.5rem;
}

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

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

.content-page h1 {
    font-size: 2.5rem;
    margin-bottom: 2rem;
    color: #333;
}

.content-page h2 {
    font-size: 1.75rem;
    margin: 2rem 0 1rem;
    color: #333;
}

.content-page p {
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

.content-page ul, .content-page ol {
    margin-bottom: 1.5rem;
    padding-left: 2rem;
}

.content-page li {
    margin-bottom: 0.5rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav {
        display: none;
    }
    
    .mobile-menu-toggle {
        display: block;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .course-info {
        grid-template-columns: 1fr;
    }
    
    .course-sidebar {
        position: static;
    }
    
    .filters-row {
        grid-template-columns: 1fr;
    }
    
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .hero-actions {
        justify-content: center;
    }
    
    .container {
        padding: 0 15px;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 2rem 0;
    }
    
    .hero h1 {
        font-size: 1.75rem;
    }
    
    .hero p {
        font-size: 1rem;
    }
    
    .section-header h2 {
        font-size: 2rem;
    }
    
    .course-card {
        margin: 0 -10px;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
}

/* Focus states for accessibility */
.btn:focus,
.form-control:focus,
a:focus {
    outline: 2px solid #6366f1;
    outline-offset: 2px;
}

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

/* Success messages */
.success-message {
    background: #d1fae5;
    color: #065f46;
    padding: 1rem;
    border-radius: 6px;
    margin-bottom: 1rem;
    border: 1px solid #a7f3d0;
}

/* Error messages */
.error-message {
    background: #fee2e2;
    color: #991b1b;
    padding: 1rem;
    border-radius: 6px;
    margin-bottom: 1rem;
    border: 1px solid #fca5a5;
}