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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #06b6d4;
    --text-dark: #1e293b;
    --text-light: #64748b;
    --bg-light: #f8fafc;
    --bg-white: #ffffff;
    --border-color: #e2e8f0;
    --success-color: #059669;
    --error-color: #dc2626;
    --warning-color: #d97706;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius: 0.5rem;
    --radius-lg: 1rem;
}

body {
    font-family: system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--bg-white);
}

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

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

.nav {
    padding: 1rem 0;
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-dark);
    font-weight: 600;
    font-size: 1.25rem;
}

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

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

.nav-menu a:hover,
.nav-menu a:focus {
    color: var(--primary-color);
}

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

.nav-toggle span {
    width: 25px;
    height: 3px;
    background: var(--text-dark);
    margin: 3px 0;
    transition: 0.3s;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    text-decoration: none;
    font-weight: 500;
    text-align: center;
    transition: all 0.2s;
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

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

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

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

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

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

.btn-secondary:hover,
.btn-secondary:focus {
    background: #475569;
}

/* Hero Section */
.hero {
    padding: 4rem 0;
    background: linear-gradient(135deg, var(--bg-light) 0%, #e0f2fe 100%);
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    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-light);
    margin-bottom: 2rem;
}

.hero-image img {
    width: 100%;
    height: auto;
}

/* Features Section */
.features {
    padding: 4rem 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-card {
    text-align: center;
    padding: 2rem;
    border-radius: var(--radius-lg);
    background: var(--bg-light);
    transition: transform 0.2s;
}

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

.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-light);
}

/* Featured Courses Section */
.featured-courses {
    padding: 4rem 0;
    background: var(--bg-light);
}

.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(300px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.course-card {
    background: var(--bg-white);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: transform 0.2s, box-shadow 0.2s;
}

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

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

.course-content {
    padding: 1.5rem;
}

.course-tag {
    display: inline-block;
    background: var(--accent-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 1rem;
}

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

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

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

.course-price {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.course-actions {
    display: flex;
    gap: 0.5rem;
}

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

/* Trust Section */
.trust-section {
    padding: 4rem 0;
    background: var(--bg-white);
}

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

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

.trust-item {
    text-align: center;
    padding: 2rem;
}

.trust-icon {
    font-size: 3rem;
    color: var(--success-color);
    margin-bottom: 1rem;
}

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

.trust-item p {
    color: var(--text-light);
}

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

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

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

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

.course-info p {
    font-size: 1.125rem;
    color: var(--text-light);
    margin-bottom: 2rem;
}

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

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

.sidebar-price {
    font-size: 2rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.sidebar-meta {
    margin-bottom: 2rem;
}

.sidebar-meta div {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

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

.course-main h2 {
    font-size: 2rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

.course-main h3 {
    font-size: 1.5rem;
    margin: 2rem 0 1rem 0;
    color: var(--text-dark);
}

.course-main ul {
    margin-bottom: 2rem;
    padding-left: 1.5rem;
}

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

.curriculum-list {
    list-style: none;
    padding: 0;
}

.curriculum-item {
    background: var(--bg-light);
    padding: 1rem;
    margin-bottom: 0.5rem;
    border-radius: var(--radius);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

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

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

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

/* Courses Page */
.courses-header {
    background: var(--bg-light);
    padding: 3rem 0;
}

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

.courses-filters {
    background: var(--bg-white);
    padding: 2rem 0;
    border-bottom: 1px solid var(--border-color);
}

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

.search-box {
    position: relative;
}

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

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

.filter-select,
.sort-select {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 1rem;
    background: var(--bg-white);
}

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

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

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

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

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

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

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

.form-section {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.form-section h2 {
    margin-bottom: 2rem;
    color: var(--text-dark);
}

.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: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 1rem;
}

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

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

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

.order-summary {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    height: fit-content;
    position: sticky;
    top: 100px;
}

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

.summary-total {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-dark);
}

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

.payment-icon {
    width: 40px;
    height: 25px;
    background: var(--border-color);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-light);
}

.security-info {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--success-color);
    font-size: 0.875rem;
    margin: 1rem 0;
}

.checkbox-group {
    display: flex;
    align-items: flex-start;
    gap: 0.5rem;
    margin: 1rem 0;
}

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

.checkbox-group label {
    font-size: 0.875rem;
    line-height: 1.4;
}

/* Success Page */
.success-content {
    padding: 4rem 0;
    text-align: center;
}

.success-icon {
    font-size: 4rem;
    color: var(--success-color);
    margin-bottom: 2rem;
}

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

.order-details {
    background: var(--bg-light);
    padding: 2rem;
    border-radius: var(--radius-lg);
    margin: 2rem 0;
    text-align: left;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

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

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

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

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

.page-content h3 {
    font-size: 1.5rem;
    margin: 1.5rem 0 0.5rem 0;
    color: var(--text-dark);
}

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

.page-content ul {
    margin-bottom: 1rem;
    padding-left: 2rem;
}

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

/* Contact Page */
.contact-info {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    margin-bottom: 3rem;
}

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

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

.contact-form {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

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

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

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
}

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

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

.footer-section a {
    color: #cbd5e1;
    text-decoration: none;
    transition: color 0.2s;
}

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

.footer-bottom {
    border-top: 1px solid #475569;
    padding-top: 1rem;
    text-align: center;
    color: #94a3b8;
}

/* 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; }

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

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

    .nav-toggle {
        display: flex;
    }

    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

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

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

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

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

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

    .course-sidebar {
        position: static;
        order: -1;
    }

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

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

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

    .contact-info {
        grid-template-columns: 1fr;
    }

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

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

@media (max-width: 480px) {
    .container {
        padding: 0 0.5rem;
    }

    .hero-content h1 {
        font-size: 1.75rem;
    }

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

    .features h2,
    .featured-courses h2,
    .trust-section h2 {
        font-size: 2rem;
    }

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

    .btn {
        padding: 0.625rem 1.25rem;
        font-size: 0.875rem;
    }
}

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

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

/* Form validation */
.form-group.error input,
.form-group.error select {
    border-color: var(--error-color);
}

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