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

:root {
    --primary-color: hsl(240, 70%, 50%);
    --primary-dark: hsl(240, 70%, 40%);
    --secondary-color: hsl(200, 70%, 50%);
    --accent-color: hsl(45, 90%, 55%);
    --text-dark: hsl(220, 20%, 20%);
    --text-light: hsl(220, 15%, 60%);
    --bg-white: #ffffff;
    --bg-light: hsl(220, 20%, 97%);
    --bg-section: hsl(220, 30%, 98%);
    --border-light: hsl(220, 20%, 90%);
    --shadow-light: 0 2px 10px hsla(220, 20%, 20%, 0.1);
    --shadow-medium: 0 4px 20px hsla(220, 20%, 20%, 0.15);
    --border-radius: 8px;
    --border-radius-large: 12px;
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --container-max-width: 1200px;
    --container-padding: 1rem;
}

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

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

/* Header */
.header {
    background: var(--bg-white);
    box-shadow: var(--shadow-light);
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.nav-link {
    text-decoration: none;
    color: var(--text-light);
    font-weight: 500;
    transition: color 0.3s ease;
    padding: 0.5rem 0;
}

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

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

.mobile-menu-btn span {
    width: 24px;
    height: 3px;
    background: var(--text-dark);
    transition: all 0.3s ease;
}

/* 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: 600;
    transition: all 0.3s ease;
    border: 2px solid transparent;
    cursor: pointer;
    font-size: 1rem;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

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

.btn-secondary:hover {
    background: hsl(200, 70%, 40%);
    transform: translateY(-2px);
}

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

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

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

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

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

.hero-content p {
    font-size: 1.25rem;
    color: var(--text-light);
    margin-bottom: 2rem;
    line-height: 1.6;
}

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

.hero-image img {
    width: 100%;
    height: auto;
    border-radius: var(--border-radius-large);
}

/* Features Section */
.features {
    padding: 5rem 0;
    background: var(--bg-white);
}

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

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

.feature {
    text-align: center;
    padding: 2rem;
    border-radius: var(--border-radius-large);
    background: var(--bg-section);
    transition: transform 0.3s ease;
}

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

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

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

.feature p {
    color: var(--text-light);
    line-height: 1.6;
}

/* Featured Courses */
.featured-courses {
    padding: 5rem 0;
    background: var(--bg-section);
}

.featured-courses h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--text-dark);
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.course-card {
    background: var(--bg-white);
    border-radius: var(--border-radius-large);
    overflow: hidden;
    box-shadow: var(--shadow-light);
    transition: all 0.3s ease;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-medium);
}

.course-image {
    position: relative;
    overflow: hidden;
}

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

.course-label {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: var(--accent-color);
    color: var(--text-dark);
    padding: 0.25rem 0.75rem;
    border-radius: var(--border-radius);
    font-size: 0.875rem;
    font-weight: 600;
}

.course-content {
    padding: 1.5rem;
}

.course-category {
    color: var(--primary-color);
    font-weight: 600;
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 0.5rem;
}

.course-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    color: var(--text-dark);
}

.course-card p {
    color: var(--text-light);
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-light);
}

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

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

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

/* Search and Filter */
.search-filter {
    padding: 2rem 0;
    background: var(--bg-white);
    border-bottom: 1px solid var(--border-light);
}

.search-filter-content {
    display: flex;
    gap: 1rem;
    align-items: center;
    flex-wrap: wrap;
}

.search-box {
    flex: 1;
    min-width: 300px;
}

.search-input {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border-light);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

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

.filter-select {
    padding: 0.75rem;
    border: 2px solid var(--border-light);
    border-radius: var(--border-radius);
    font-size: 1rem;
    background: var(--bg-white);
    cursor: pointer;
    transition: border-color 0.3s ease;
}

.filter-select:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Course Detail Page */
.course-header {
    padding: 3rem 0;
    background: var(--bg-section);
}

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

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

.course-subtitle {
    font-size: 1.25rem;
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

.course-tags {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-bottom: 2rem;
}

.tag {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--border-radius);
    font-size: 0.875rem;
}

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

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

.course-details {
    padding: 3rem 0;
}

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

.course-section h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-dark);
}

.course-section h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

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

.course-section li {
    padding: 0.5rem 0;
    padding-left: 1.5rem;
    position: relative;
}

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

.curriculum-item {
    background: var(--bg-section);
    padding: 1rem;
    margin-bottom: 0.5rem;
    border-radius: var(--border-radius);
    border-left: 4px solid var(--primary-color);
}

.instructor-card {
    background: var(--bg-section);
    padding: 2rem;
    border-radius: var(--border-radius-large);
    margin-top: 2rem;
}

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

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

.faq-answer {
    padding: 1rem;
    display: none;
}

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

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

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

.form-input,
.form-textarea {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border-light);
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.3s ease;
}

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

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

/* Footer */
.footer {
    background: var(--text-dark);
    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: white;
}

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

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

.footer-section a {
    color: hsl(220, 15%, 70%);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

.footer-bottom {
    border-top: 1px solid hsl(220, 20%, 30%);
    padding-top: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: start;
    gap: 2rem;
}

.footer-info p {
    margin-bottom: 0.25rem;
    color: hsl(220, 15%, 70%);
    font-size: 0.875rem;
}

.footer-info a {
    color: hsl(220, 15%, 70%);
    text-decoration: none;
}

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

.copyright {
    text-align: right;
}

.copyright p {
    color: hsl(220, 15%, 60%);
    font-size: 0.875rem;
}

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

.page-title {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

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

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

.content-section h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-dark);
}

.content-section h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

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

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

.content-section li {
    margin-bottom: 0.5rem;
    color: var(--text-light);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .hero .container {
        grid-template-columns: 1fr;
        gap: 2rem;
        text-align: center;
    }
    
    .hero-content h1 {
        font-size: 2rem;
    }
    
    .hero-content p {
        font-size: 1.1rem;
    }
    
    .features h2,
    .featured-courses h2 {
        font-size: 2rem;
    }
    
    .course-header-content {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
    
    .course-title {
        font-size: 2rem;
    }
    
    .search-filter-content {
        flex-direction: column;
        align-items: stretch;
    }
    
    .search-box {
        min-width: auto;
    }
    
    .footer-bottom {
        flex-direction: column;
        text-align: left;
    }
    
    .copyright {
        text-align: left;
    }
    
    .hero-actions {
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 1rem;
    }
    
    .hero {
        padding: 2rem 0;
    }
    
    .features,
    .featured-courses {
        padding: 3rem 0;
    }
    
    .course-header {
        padding: 2rem 0;
    }
    
    .course-details {
        padding: 2rem 0;
    }
    
    .btn {
        padding: 0.625rem 1.25rem;
        font-size: 0.9rem;
    }
}

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