/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

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

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

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    margin-bottom: 0.5rem;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p {
    margin-bottom: 1rem;
}

a {
    color: #6366f1;
    text-decoration: none;
    transition: color 0.3s ease;
}

a:hover {
    color: #4f46e5;
}

img {
    max-width: 100%;
    height: auto;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 0.5rem;
    font-size: 1rem;
    font-weight: 500;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
}

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

.btn-primary:hover {
    background-color: #4f46e5;
    color: white;
}

.btn-secondary {
    background-color: #f3f4f6;
    color: #374151;
    border: 1px solid #d1d5db;
}

.btn-secondary:hover {
    background-color: #e5e7eb;
    color: #374151;
}

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

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

.btn-success {
    background-color: #10b981;
    color: white;
}

.btn-success:hover {
    background-color: #059669;
    color: white;
}

/* Header */
.header {
    background-color: #fff;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.logo {
    width: 40px;
    height: 40px;
}

.brand-text {
    font-size: 1.25rem;
    font-weight: 600;
    color: #1f2937;
}

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

.nav-link {
    color: #4b5563;
    font-weight: 500;
    padding: 0.5rem 0;
    position: relative;
    transition: color 0.3s ease;
}

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -0.25rem;
    left: 0;
    right: 0;
    height: 2px;
    background-color: #6366f1;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    gap: 0.25rem;
}

.nav-toggle span {
    width: 25px;
    height: 3px;
    background-color: #4b5563;
    transition: all 0.3s ease;
}

/* Hero Section */
.hero {
    position: relative;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 0;
    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 {
    position: relative;
    z-index: 2;
    text-align: center;
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 3rem;
    margin-bottom: 1.5rem;
    font-weight: 700;
}

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

.hero-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: 3rem;
}

.hero-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    max-width: 600px;
    margin: 0 auto;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    background: rgba(255, 255, 255, 0.1);
    padding: 1rem;
    border-radius: 0.5rem;
    backdrop-filter: blur(10px);
}

.feature-icon {
    font-size: 1.5rem;
}

/* Sections */
.section {
    padding: 4rem 0;
}

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

.section-title {
    margin-bottom: 1rem;
    color: #1f2937;
}

.section-description {
    color: #6b7280;
    font-size: 1.125rem;
    max-width: 600px;
    margin: 0 auto;
}

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

/* Featured Courses */
.featured-courses {
    padding: 4rem 0;
    background-color: #f9fafb;
}

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

.course-card {
    background: white;
    border-radius: 1rem;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.course-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
}

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

.course-content {
    padding: 1.5rem;
}

.course-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.course-category {
    background-color: #e0e7ff;
    color: #6366f1;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.875rem;
    font-weight: 500;
}

.course-difficulty {
    background-color: #f3f4f6;
    color: #6b7280;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.875rem;
}

.course-title {
    margin-bottom: 0.75rem;
    color: #1f2937;
}

.course-description {
    color: #6b7280;
    margin-bottom: 1rem;
    font-size: 0.9375rem;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    font-size: 0.875rem;
    color: #6b7280;
}

.course-price {
    font-size: 1.5rem;
    font-weight: 600;
    color: #059669;
    margin-bottom: 1rem;
}

.course-actions {
    display: flex;
    gap: 0.75rem;
}

.course-actions .btn {
    flex: 1;
    text-align: center;
}

/* Why Choose Section */
.why-choose {
    padding: 4rem 0;
}

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

.feature-card {
    text-align: center;
    padding: 2rem 1.5rem;
    border-radius: 1rem;
    background: white;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    transition: transform 0.3s ease;
}

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

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

.feature-card h3 {
    margin-bottom: 1rem;
    color: #1f2937;
}

.feature-card p {
    color: #6b7280;
    margin-bottom: 0;
}

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

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

.course-detail-main {
    background: white;
    border-radius: 1rem;
    padding: 2rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

.course-detail-sidebar {
    background: white;
    border-radius: 1rem;
    padding: 2rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    height: fit-content;
    position: sticky;
    top: 100px;
}

.course-detail-image {
    width: 100%;
    height: 300px;
    object-fit: cover;
    border-radius: 0.75rem;
    margin-bottom: 2rem;
}

.course-tags {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.course-tag {
    background-color: #f3f4f6;
    color: #6b7280;
    padding: 0.5rem 1rem;
    border-radius: 1rem;
    font-size: 0.875rem;
}

.course-detail-title {
    margin-bottom: 1rem;
}

.course-instructor {
    background-color: #f9fafb;
    padding: 1.5rem;
    border-radius: 0.75rem;
    margin: 2rem 0;
}

.instructor-name {
    font-weight: 600;
    color: #1f2937;
    margin-bottom: 0.5rem;
}

.what-you-learn,
.requirements,
.curriculum,
.course-faq {
    margin: 2rem 0;
}

.what-you-learn h3,
.requirements h3,
.curriculum h3,
.course-faq h3 {
    margin-bottom: 1rem;
    color: #1f2937;
}

.what-you-learn ul,
.requirements ul {
    list-style: none;
    padding: 0;
}

.what-you-learn li,
.requirements li {
    padding: 0.5rem 0;
    position: relative;
    padding-left: 1.5rem;
}

.what-you-learn li:before {
    content: '✓';
    position: absolute;
    left: 0;
    color: #10b981;
    font-weight: bold;
}

.requirements li:before {
    content: '•';
    position: absolute;
    left: 0;
    color: #6b7280;
}

.curriculum-item {
    background-color: #f9fafb;
    padding: 1rem;
    border-radius: 0.5rem;
    margin-bottom: 0.75rem;
    border-left: 4px solid #6366f1;
}

.lesson-title {
    font-weight: 500;
    color: #1f2937;
}

.faq-item {
    margin-bottom: 1.5rem;
}

.faq-question {
    font-weight: 600;
    color: #1f2937;
    margin-bottom: 0.5rem;
}

.faq-answer {
    color: #6b7280;
    margin-bottom: 0;
}

/* Courses Page */
.courses-header {
    background-color: #f9fafb;
    padding: 3rem 0;
}

.courses-filters {
    background: white;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    margin-bottom: 2rem;
}

.filters-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 1.5rem;
    align-items: end;
}

.filter-group {
    display: flex;
    flex-direction: column;
}

.filter-group label {
    font-weight: 500;
    color: #374151;
    margin-bottom: 0.5rem;
}

.filter-group input,
.filter-group select {
    padding: 0.75rem;
    border: 1px solid #d1d5db;
    border-radius: 0.5rem;
    font-size: 1rem;
}

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

.courses-results {
    padding: 2rem 0;
}

.results-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

.results-count {
    color: #6b7280;
}

/* Checkout Pages */
.checkout-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

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

.step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    background-color: #f3f4f6;
    color: #6b7280;
    border-radius: 2rem;
    margin: 0 0.5rem;
}

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

.step.completed {
    background-color: #10b981;
    color: white;
}

.checkout-form {
    background: white;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    margin-bottom: 2rem;
}

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

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group.full-width {
    grid-column: 1 / -1;
}

.form-group label {
    font-weight: 500;
    color: #374151;
    margin-bottom: 0.5rem;
}

.form-group input,
.form-group select,
.form-group textarea {
    padding: 0.75rem;
    border: 1px solid #d1d5db;
    border-radius: 0.5rem;
    font-size: 1rem;
}

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

.form-error {
    color: #ef4444;
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

.order-summary {
    background: white;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    margin-bottom: 2rem;
}

.summary-item {
    display: flex;
    justify-content: space-between;
    padding: 1rem 0;
    border-bottom: 1px solid #e5e7eb;
}

.summary-item:last-child {
    border-bottom: none;
    font-weight: 600;
    font-size: 1.125rem;
}

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

.payment-icon {
    width: 40px;
    height: 25px;
}

.security-note {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: #6b7280;
    font-size: 0.875rem;
    margin: 1rem 0;
}

.checkbox-group {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    margin: 1.5rem 0;
}

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

/* Footer */
.footer {
    background-color: #1f2937;
    color: #d1d5db;
    padding: 3rem 0 1rem;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
    gap: 2rem;
    margin-bottom: 2rem;
}

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

.footer-brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.footer-logo {
    width: 40px;
    height: 40px;
}

.footer-brand-text {
    font-size: 1.25rem;
    font-weight: 600;
    color: white;
}

.footer-description {
    color: #9ca3af;
    margin-bottom: 0;
}

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

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

.footer-links a {
    color: #d1d5db;
    transition: color 0.3s ease;
}

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

.contact-info p {
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.contact-info a {
    color: #d1d5db;
}

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

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

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 70px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 70px);
        background-color: white;
        flex-direction: column;
        justify-content: flex-start;
        align-items: center;
        padding: 2rem;
        transition: left 0.3s ease;
        box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    }

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

    .nav-toggle {
        display: flex;
    }

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

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

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

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

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

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

    .course-detail-sidebar {
        position: static;
    }

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

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

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

    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    h3 { font-size: 1.25rem; }
}

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

    .hero {
        padding: 2rem 0;
    }

    .hero-title {
        font-size: 1.75rem;
    }

    .section {
        padding: 2rem 0;
    }

    .featured-courses {
        padding: 2rem 0;
    }

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

    .checkout-form,
    .order-summary {
        padding: 1.5rem;
    }
}

/* Utility Classes */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }

.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }
.d-grid { display: grid; }

/* Focus and Accessibility */
*:focus {
    outline: 2px solid #6366f1;
    outline-offset: 2px;
}

.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;
}

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

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    margin: -10px 0 0 -10px;
    border: 2px solid #f3f3f3;
    border-top: 2px solid #6366f1;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}