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

:root {
    --primary-color: hsl(240, 70%, 60%);
    --primary-hover: hsl(240, 70%, 55%);
    --secondary-color: hsl(200, 70%, 50%);
    --accent-color: hsl(280, 60%, 55%);
    --text-dark: hsl(210, 20%, 15%);
    --text-medium: hsl(210, 15%, 45%);
    --text-light: hsl(210, 15%, 65%);
    --bg-white: hsl(0, 0%, 100%);
    --bg-light: hsl(210, 20%, 98%);
    --bg-section: hsl(210, 20%, 96%);
    --border-light: hsl(210, 20%, 90%);
    --shadow-light: 0 2px 8px hsla(210, 20%, 0%, 0.08);
    --shadow-medium: 0 4px 16px hsla(210, 20%, 0%, 0.12);
    --border-radius: 8px;
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--bg-white);
}

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

/* Header */
.header {
    background: var(--bg-white);
    box-shadow: var(--shadow-light);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 20px;
    max-width: 1200px;
    margin: 0 auto;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--text-dark);
    font-weight: 700;
    font-size: 1.25rem;
}

.nav-menu {
    display: flex;
    gap: 2rem;
    align-items: center;
}

.nav-link {
    text-decoration: none;
    color: var(--text-medium);
    font-weight: 500;
    transition: var(--transition);
    padding: 0.5rem 0;
    position: relative;
}

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary-color);
    border-radius: 1px;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-dark);
    transition: var(--transition);
}

/* Hero */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 6rem 0;
    position: relative;
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    opacity: 0.1;
    z-index: 1;
}

.hero-bg-image {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.hero-content {
    text-align: center;
    position: relative;
    z-index: 2;
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
    margin-bottom: 1.5rem;
    line-height: 1.2;
}

.hero-subtitle {
    font-size: 1.25rem;
    margin-bottom: 2.5rem;
    opacity: 0.9;
    line-height: 1.6;
}

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

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 600;
    font-size: 1rem;
    transition: var(--transition);
    border: 2px solid transparent;
    cursor: pointer;
    text-align: center;
}

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

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

.btn-secondary {
    background: transparent;
    color: white;
    border-color: white;
}

.btn-secondary:hover {
    background: white;
    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;
}

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

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

.feature-card {
    text-align: center;
    padding: 2rem;
    background: var(--bg-white);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-light);
    transition: var(--transition);
}

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

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

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

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

/* Featured Courses */
.featured-courses {
    padding: 5rem 0;
}

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

.section-header h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

.section-header p {
    font-size: 1.125rem;
    color: var(--text-medium);
    max-width: 600px;
    margin: 0 auto;
}

.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-light);
    transition: var(--transition);
}

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

.course-image {
    position: relative;
    height: 200px;
    overflow: hidden;
}

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

.course-badge {
    position: absolute;
    top: 12px;
    right: 12px;
    background: var(--primary-color);
    color: white;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 600;
}

.course-content {
    padding: 1.5rem;
}

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

.course-category {
    background: var(--bg-section);
    padding: 4px 12px;
    border-radius: 20px;
    font-weight: 500;
}

.course-title {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    color: var(--text-dark);
    line-height: 1.4;
}

.course-description {
    color: var(--text-medium);
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.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-footer {
    text-align: center;
}

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

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

.search-box {
    position: relative;
    flex: 1;
    max-width: 400px;
}

.search-input {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border-light);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: var(--transition);
}

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

.category-filter {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 8px 16px;
    background: var(--bg-white);
    border: 2px solid var(--border-light);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.875rem;
    font-weight: 500;
}

.filter-btn:hover,
.filter-btn.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

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

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

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

.course-main h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

.course-main p {
    font-size: 1.125rem;
    color: var(--text-medium);
    margin-bottom: 2rem;
    line-height: 1.6;
}

.course-meta-detail {
    display: flex;
    gap: 2rem;
    margin-bottom: 2rem;
}

.meta-item {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.meta-label {
    font-size: 0.875rem;
    color: var(--text-light);
    font-weight: 500;
}

.meta-value {
    font-weight: 600;
    color: var(--text-dark);
}

.course-sidebar {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-light);
    height: fit-content;
}

.course-price-large {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

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

.course-features li {
    padding: 8px 0;
    color: var(--text-medium);
    display: flex;
    align-items: center;
    gap: 8px;
}

.course-features li::before {
    content: '✓';
    color: var(--primary-color);
    font-weight: 600;
}

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

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

.course-section h2 {
    font-size: 1.75rem;
    margin-bottom: 1.5rem;
    color: var(--text-dark);
}

.course-section h3 {
    font-size: 1.25rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

.course-section ul {
    list-style-position: inside;
    color: var(--text-medium);
    line-height: 1.8;
}

.curriculum-list {
    list-style: none;
}

.curriculum-item {
    background: var(--bg-light);
    padding: 1rem;
    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-dark);
}

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

.instructor-card {
    background: var(--bg-light);
    padding: 2rem;
    border-radius: var(--border-radius);
    text-align: center;
}

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

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

.faq-list {
    list-style: none;
}

.faq-item {
    border-bottom: 1px solid var(--border-light);
    padding: 1.5rem 0;
}

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

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

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

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

.form-input,
.form-textarea {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border-light);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: var(--transition);
    font-family: inherit;
}

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

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

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

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

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

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

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

.content-page ul,
.content-page ol {
    margin-bottom: 1rem;
    padding-left: 2rem;
    color: var(--text-medium);
    line-height: 1.7;
}

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

/* 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-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 700;
    font-size: 1.25rem;
    margin-bottom: 1rem;
}

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

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

.footer-links {
    list-style: none;
}

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

.footer-links a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: var(--transition);
}

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

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

.contact-info a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: var(--transition);
}

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

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
}

/* Responsive */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 70px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 70px);
        background: var(--bg-white);
        flex-direction: column;
        justify-content: flex-start;
        padding: 2rem;
        transition: var(--transition);
        box-shadow: var(--shadow-medium);
    }

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

    .nav-toggle {
        display: flex;
    }

    .hero {
        padding: 4rem 0;
    }

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

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

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

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

    .search-box {
        max-width: none;
    }

    .category-filter {
        justify-content: center;
    }

    .course-meta-detail {
        flex-direction: column;
        gap: 1rem;
    }

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }

    .nav-container {
        padding: 1rem 15px;
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1.125rem;
    }

    .courses-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }

    .course-card {
        margin: 0 -5px;
    }

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

    .btn {
        padding: 10px 20px;
        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 */
*:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

.btn:focus,
.nav-link:focus,
.form-input:focus,
.form-textarea:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}