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

:root {
    --primary-color: hsl(220, 70%, 50%);
    --primary-dark: hsl(220, 70%, 40%);
    --secondary-color: hsl(280, 60%, 50%);
    --accent-color: hsl(45, 100%, 60%);
    --text-dark: hsl(220, 20%, 20%);
    --text-medium: hsl(220, 15%, 40%);
    --text-light: hsl(220, 10%, 60%);
    --border-color: hsl(220, 20%, 90%);
    --bg-light: hsl(220, 30%, 98%);
    --bg-white: #ffffff;
    --success-color: hsl(120, 50%, 50%);
    --error-color: hsl(0, 60%, 50%);
    --shadow-light: 0 2px 10px rgba(0, 0, 0, 0.1);
    --shadow-medium: 0 4px 20px rgba(0, 0, 0, 0.15);
    --border-radius: 8px;
    --border-radius-large: 12px;
    --max-width: 1200px;
    --header-height: 70px;
}

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: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

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

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--text-dark);
}

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

.nav {
    display: flex;
    gap: 2rem;
}

.nav-link {
    text-decoration: none;
    color: var(--text-medium);
    font-weight: 500;
    padding: 8px 0;
    border-bottom: 2px solid transparent;
    transition: all 0.3s ease;
}

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

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

.mobile-menu-btn span {
    width: 24px;
    height: 2px;
    background: var(--text-dark);
    transition: all 0.3s ease;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
    justify-content: center;
}

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

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

.btn-secondary {
    background: var(--bg-light);
    color: var(--text-dark);
    border: 2px solid var(--border-color);
}

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

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

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

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

.btn-success:hover {
    background: hsl(120, 50%, 40%);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none !important;
}

/* Hero Section */
.hero {
    padding: 80px 0;
    background: linear-gradient(135deg, var(--bg-light) 0%, var(--bg-white) 100%);
}

.hero-content {
    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-dark);
}

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

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

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

/* Features Section */
.features {
    padding: 80px 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(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    padding: 2rem;
    background: var(--bg-white);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-large);
    text-align: center;
    transition: all 0.3s ease;
}

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

/* Sections */
.featured-courses,
.courses-section {
    padding: 80px 0;
    background: var(--bg-light);
}

.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: 1.25rem;
    color: var(--text-medium);
}

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

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

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

.course-content {
    padding: 1.5rem;
}

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

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

.course-description {
    color: var(--text-medium);
    margin-bottom: 1rem;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

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

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

.course-tag {
    display: inline-block;
    padding: 4px 12px;
    background: var(--accent-color);
    color: var(--text-dark);
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 1rem;
}

/* Course Filters */
.course-filters {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    align-items: center;
}

.filter-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.filter-group label {
    font-weight: 500;
    color: var(--text-dark);
}

.filter-group select,
.filter-group input {
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

/* Course Detail */
.course-detail {
    padding: 40px 0;
}

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

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

.course-sidebar {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--border-radius-large);
    box-shadow: var(--shadow-light);
    height: fit-content;
    position: sticky;
    top: calc(var(--header-height) + 20px);
}

.course-sidebar img {
    width: 100%;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
}

.course-sidebar .course-price {
    font-size: 2rem;
    margin-bottom: 1rem;
}

.course-tabs {
    margin-bottom: 2rem;
}

.tab-buttons {
    display: flex;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 2rem;
    overflow-x: auto;
}

.tab-button {
    padding: 12px 24px;
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-medium);
    border-bottom: 2px solid transparent;
    white-space: nowrap;
    transition: all 0.3s ease;
}

.tab-button.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.curriculum-list,
.requirements-list,
.learning-list {
    list-style: none;
}

.curriculum-list li,
.requirements-list li,
.learning-list li {
    padding: 12px 0;
    border-bottom: 1px solid var(--border-color);
    position: relative;
    padding-left: 2rem;
}

.curriculum-list li::before,
.learning-list li::before {
    content: "✓";
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

.requirements-list li::before {
    content: "•";
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

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

.instructor-card h3 {
    color: var(--text-dark);
    margin-bottom: 1rem;
}

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

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

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

.faq-answer {
    padding: 1rem;
    background: var(--bg-white);
    display: none;
}

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

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

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

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: border-color 0.3s 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(59, 130, 246, 0.1);
}

.form-group.error input,
.form-group.error select,
.form-group.error textarea {
    border-color: var(--error-color);
}

.form-error {
    color: var(--error-color);
    font-size: 0.875rem;
    margin-top: 0.25rem;
    display: none;
}

.form-group.error .form-error {
    display: block;
}

.checkbox-group {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

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

.checkbox-group label {
    margin: 0;
    font-weight: normal;
    cursor: pointer;
}

/* Checkout */
.checkout-section {
    padding: 40px 0;
}

.checkout-steps {
    display: flex;
    justify-content: center;
    margin-bottom: 3rem;
    gap: 2rem;
}

.step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 12px 24px;
    background: var(--bg-light);
    border-radius: var(--border-radius);
    color: var(--text-medium);
}

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

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

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

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

.checkout-summary {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--border-radius-large);
    box-shadow: var(--shadow-light);
    height: fit-content;
    position: sticky;
    top: calc(var(--header-height) + 20px);
}

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

.summary-item:last-child {
    border-bottom: none;
    font-weight: 600;
    font-size: 1.25rem;
}

.payment-icons {
    display: flex;
    gap: 1rem;
    align-items: center;
    margin: 1rem 0;
}

.payment-icon {
    width: 40px;
    height: 25px;
    background: var(--bg-light);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: bold;
    color: var(--text-medium);
}

.security-badge {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--success-color);
    font-size: 0.875rem;
    margin-top: 1rem;
}

/* CTA Section */
.cta {
    padding: 80px 0;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    text-align: center;
}

.cta-content h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

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

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

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

/* Footer */
.footer {
    background: var(--text-dark);
    color: white;
    padding: 60px 0 20px;
}

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

.footer-section a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

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

.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);
}

/* Content Pages */
.content-page {
    padding: 40px 0;
}

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

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

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

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

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

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

.alert {
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
}

.alert-success {
    background: hsl(120, 50%, 95%);
    border: 1px solid hsl(120, 50%, 80%);
    color: hsl(120, 50%, 30%);
}

.alert-error {
    background: hsl(0, 60%, 95%);
    border: 1px solid hsl(0, 60%, 80%);
    color: hsl(0, 60%, 30%);
}

.alert-info {
    background: hsl(220, 70%, 95%);
    border: 1px solid hsl(220, 70%, 80%);
    color: hsl(220, 70%, 30%);
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 0 15px;
    }
    
    .nav {
        display: none;
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        gap: 2rem;
        text-align: center;
    }
    
    .hero-content h1 {
        font-size: 2rem;
    }
    
    .hero-buttons {
        justify-content: center;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .course-header {
        grid-template-columns: 1fr;
    }
    
    .checkout-content {
        grid-template-columns: 1fr;
    }
    
    .checkout-steps {
        flex-direction: column;
        align-items: center;
    }
    
    .tab-buttons {
        justify-content: flex-start;
    }
    
    .course-filters {
        flex-direction: column;
        align-items: stretch;
    }
    
    .filter-group {
        flex-direction: column;
        align-items: stretch;
    }
}

@media (max-width: 480px) {
    .hero-content h1 {
        font-size: 1.75rem;
    }
    
    .section-header h2 {
        font-size: 2rem;
    }
    
    .features h2 {
        font-size: 2rem;
    }
    
    .cta-content h2 {
        font-size: 2rem;
    }
    
    .btn {
        padding: 10px 20px;
        font-size: 0.9rem;
    }
    
    .hero-buttons {
        flex-direction: column;
        width: 100%;
    }
    
    .hero-buttons .btn {
        width: 100%;
    }
}

/* Print Styles */
@media print {
    .header,
    .footer,
    .cta,
    .mobile-menu-btn,
    .btn {
        display: none !important;
    }
    
    body {
        font-size: 12pt;
        line-height: 1.4;
    }
    
    .container {
        max-width: none;
        padding: 0;
    }
}