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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #f59e0b;
    --text-color: #1f2937;
    --text-light: #6b7280;
    --background: #ffffff;
    --background-light: #f8fafc;
    --border-color: #e5e7eb;
    --success-color: #10b981;
    --error-color: #ef4444;
    --border-radius: 8px;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

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

/* Header */
.header {
    background: var(--background);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 4rem;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-color);
    font-weight: 600;
    font-size: 1.125rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

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

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

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

.nav-toggle span {
    width: 1.5rem;
    height: 2px;
    background: var(--text-color);
    margin: 2px 0;
    transition: 0.3s;
}

/* 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: 500;
    transition: all 0.2s;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    gap: 0.5rem;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

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

.btn-secondary:hover {
    background: #475569;
    transform: translateY(-1px);
}

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

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

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.125rem;
}

.btn-full {
    width: 100%;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 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 img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

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

.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;
    justify-content: center;
    flex-wrap: wrap;
}

/* Features */
.features {
    padding: 4rem 0;
    background: var(--background-light);
}

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

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--background);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    text-align: center;
    transition: transform 0.2s;
}

.feature-card:hover {
    transform: translateY(-4px);
}

.feature-icon {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

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

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

/* Courses */
.featured-courses {
    padding: 4rem 0;
}

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

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

.section-header p {
    font-size: 1.125rem;
    color: var(--text-light);
}

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

.course-card {
    background: var(--background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: transform 0.2s, box-shadow 0.2s;
    text-decoration: none;
    color: inherit;
}

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

.course-image {
    width: 100%;
    height: 200px;
    background: linear-gradient(45deg, var(--primary-color), var(--accent-color));
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
}

.course-image img {
    width: 80px;
    height: 80px;
}

.course-content {
    padding: 1.5rem;
}

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

.course-tag {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.75rem;
    font-weight: 500;
}

.course-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.course-card p {
    color: var(--text-light);
    margin-bottom: 1rem;
    line-height: 1.5;
}

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

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

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

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

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

.trust-indicators h2 {
    text-align: center;
    font-size: 2rem;
    margin-bottom: 2rem;
    color: var(--text-color);
}

.trust-grid {
    display: flex;
    justify-content: center;
    gap: 3rem;
    flex-wrap: wrap;
}

.trust-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--text-color);
    font-weight: 500;
}

.trust-item svg {
    color: var(--success-color);
}

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

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

.form-input,
.form-select,
.form-textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

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

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

.form-error {
    color: var(--error-color);
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

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

.form-checkbox input {
    margin-top: 0.25rem;
}

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

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

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

.course-subtitle {
    font-size: 1.25rem;
    color: var(--text-light);
    margin-bottom: 2rem;
}

.course-details {
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 3rem;
}

.course-main {
    background: var(--background);
}

.course-sidebar {
    background: var(--background);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    height: fit-content;
    position: sticky;
    top: 5rem;
}

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

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

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

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

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

.course-list li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

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

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

.curriculum-item h4 {
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

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

.instructor-card {
    background: var(--background-light);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    margin-bottom: 2rem;
}

.instructor-card h3 {
    color: var(--text-color);
    margin-bottom: 0.5rem;
}

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

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

.faq-question {
    width: 100%;
    padding: 1rem;
    background: none;
    border: none;
    text-align: left;
    font-weight: 500;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.faq-question:hover {
    background: var(--background-light);
}

.faq-answer {
    padding: 0 1rem 1rem;
    color: var(--text-light);
    display: none;
}

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

/* Checkout */
.checkout-header {
    background: var(--background-light);
    padding: 2rem 0;
    margin-bottom: 2rem;
}

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

.checkout-step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border-radius: var(--border-radius);
    background: var(--background);
    color: var(--text-light);
}

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

.checkout-content {
    display: grid;
    grid-template-columns: 1fr 400px;
    gap: 3rem;
    max-width: 1000px;
    margin: 0 auto;
}

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

.checkout-summary {
    background: var(--background-light);
    padding: 2rem;
    border-radius: var(--border-radius);
    height: fit-content;
    position: sticky;
    top: 5rem;
}

.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: 1.125rem;
}

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

.payment-icon {
    width: 40px;
    height: 24px;
    background: var(--background);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
}

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

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

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

.footer-section h3 {
    margin-bottom: 1rem;
    color: white;
}

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

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

.footer-section a {
    color: #d1d5db;
    text-decoration: none;
    transition: color 0.2s;
}

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

.footer-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
    font-size: 1.125rem;
}

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

/* Responsive */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--background);
        border-top: 1px solid var(--border-color);
        flex-direction: column;
        padding: 1rem;
        gap: 1rem;
    }

    .nav-menu.active {
        display: flex;
    }

    .nav-toggle {
        display: flex;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 1rem;
    }

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

    .features h2,
    .section-header h2 {
        font-size: 2rem;
    }

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

    .course-details {
        grid-template-columns: 1fr;
    }

    .course-sidebar {
        position: static;
    }

    .checkout-content {
        grid-template-columns: 1fr;
    }

    .checkout-summary {
        position: static;
        order: -1;
    }

    .checkout-steps {
        flex-direction: column;
        align-items: center;
    }

    .trust-grid {
        flex-direction: column;
        align-items: center;
        gap: 1.5rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 0.75rem;
    }

    .hero {
        padding: 2rem 0;
    }

    .features,
    .featured-courses,
    .trust-indicators {
        padding: 2rem 0;
    }

    .course-card,
    .feature-card {
        margin: 0 0.5rem;
    }

    .courses-grid {
        grid-template-columns: 1fr;
        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 */
*:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

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