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

:root {
    --primary-color: hsl(220, 70%, 50%);
    --primary-dark: hsl(220, 70%, 40%);
    --primary-light: hsl(220, 70%, 95%);
    --secondary-color: hsl(160, 60%, 50%);
    --accent-color: hsl(40, 90%, 60%);
    --text-dark: hsl(220, 20%, 20%);
    --text-medium: hsl(220, 10%, 40%);
    --text-light: hsl(220, 10%, 60%);
    --border-color: hsl(220, 20%, 90%);
    --bg-light: hsl(220, 30%, 98%);
    --bg-white: #ffffff;
    --shadow-light: 0 2px 10px hsla(220, 20%, 20%, 0.1);
    --shadow-medium: 0 4px 20px hsla(220, 20%, 20%, 0.15);
    --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: 100;
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-dark);
    font-weight: 600;
    font-size: 1.2rem;
}

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

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

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -0.5rem;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary-color);
}

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

.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-dark);
    margin: 2px 0;
    transition: var(--transition);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 500;
    text-align: center;
    cursor: pointer;
    border: 2px solid transparent;
    transition: var(--transition);
    font-size: 1rem;
    line-height: 1;
}

.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(--secondary-color);
    color: white;
}

.btn-secondary:hover {
    background: hsl(160, 60%, 40%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-medium);
}

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

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

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

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

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

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
}

.hero-content h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-dark);
    line-height: 1.2;
}

.hero-content p {
    font-size: 1.2rem;
    color: var(--text-medium);
    margin-bottom: 2rem;
    max-width: 500px;
}

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

.hero-image img {
    width: 100%;
    height: auto;
    max-width: 500px;
}

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

.features h2 {
    text-align: center;
    font-size: 2rem;
    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 1.5rem;
    background: var(--bg-white);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-light);
    transition: var(--transition);
}

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

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

.feature-card h3 {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

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

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

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

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

.section-header p {
    font-size: 1.1rem;
    color: var(--text-medium);
    margin-bottom: 2rem;
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.course-card {
    background: var(--bg-white);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-light);
    transition: var(--transition);
    text-decoration: none;
    color: inherit;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-medium);
    text-decoration: none;
    color: inherit;
}

.course-image {
    width: 100%;
    height: 200px;
    object-fit: cover;
    background: var(--primary-light);
}

.course-content {
    padding: 1.5rem;
}

.course-meta {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    font-size: 0.9rem;
    color: var(--text-light);
}

.course-title {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-dark);
    line-height: 1.3;
}

.course-description {
    color: var(--text-medium);
    margin-bottom: 1rem;
    line-height: 1.5;
}

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

.course-price {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
}

.course-tag {
    background: var(--accent-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
}

/* Trust Indicators */
.trust-indicators {
    padding: 3rem 0;
    background: var(--bg-white);
}

.trust-indicators h2 {
    text-align: center;
    font-size: 1.8rem;
    margin-bottom: 2rem;
    color: var(--text-dark);
}

.trust-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
}

.trust-item {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    padding: 1rem;
    background: var(--bg-light);
    border-radius: var(--border-radius);
    color: var(--text-medium);
    font-weight: 500;
}

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

/* 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: 2.2rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
    line-height: 1.2;
}

.course-info .course-meta {
    margin-bottom: 1.5rem;
}

.course-info .course-description {
    font-size: 1.1rem;
    margin-bottom: 2rem;
}

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

.course-price-display {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

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

.course-features li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.course-features li:last-child {
    border-bottom: none;
}

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

.course-main {
    space-y: 2rem;
}

.course-section {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-light);
    margin-bottom: 2rem;
}

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

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

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

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

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

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

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

.faq-item:last-child {
    border-bottom: none;
}

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

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

/* Courses Page */
.courses-page {
    padding: 2rem 0;
}

.courses-header {
    background: var(--bg-light);
    padding: 2rem 0;
    margin-bottom: 3rem;
}

.courses-header h1 {
    font-size: 2.2rem;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

.courses-filters {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    align-items: center;
    margin-bottom: 2rem;
}

.search-box {
    flex: 1;
    min-width: 250px;
}

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

.filter-select {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    background: var(--bg-white);
    min-width: 150px;
}

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

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

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

.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px hsla(220, 70%, 50%, 0.1);
}

.form-input.error {
    border-color: hsl(0, 70%, 50%);
}

.form-error {
    color: hsl(0, 70%, 50%);
    font-size: 0.9rem;
    margin-top: 0.25rem;
}

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

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

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

/* Checkout */
.checkout-page {
    padding: 2rem 0;
}

.checkout-container {
    max-width: 800px;
    margin: 0 auto;
}

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

.step {
    display: flex;
    align-items: center;
    padding: 1rem 2rem;
    background: var(--bg-light);
    color: var(--text-light);
    position: relative;
}

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

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

.step:not(:last-child)::after {
    content: '';
    position: absolute;
    right: -10px;
    top: 50%;
    transform: translateY(-50%);
    width: 0;
    height: 0;
    border-left: 10px solid;
    border-top: 20px solid transparent;
    border-bottom: 20px solid transparent;
    z-index: 1;
}

.step.active::after {
    border-left-color: var(--primary-color);
}

.step.completed::after {
    border-left-color: var(--secondary-color);
}

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

.order-summary {
    background: var(--bg-light);
    padding: 2rem;
    border-radius: var(--border-radius);
    margin-bottom: 2rem;
}

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

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

.order-item:last-child {
    border-bottom: none;
    font-weight: 600;
    font-size: 1.1rem;
}

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

.payment-icon {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--bg-white);
}

/* Footer */
.footer {
    background: var(--text-dark);
    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 h4 {
    margin-bottom: 1rem;
    color: white;
}

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

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

.footer-section a {
    color: hsl(220, 10%, 80%);
    text-decoration: none;
    transition: var(--transition);
}

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

.footer-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
    font-size: 1.2rem;
}

.footer-bottom {
    border-top: 1px solid hsl(220, 10%, 30%);
    padding-top: 1rem;
    text-align: center;
    color: hsl(220, 10%, 70%);
}

/* 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-medium);
        flex-direction: column;
        padding: 1rem 0;
        gap: 0;
    }

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

    .nav-menu li {
        padding: 0.5rem 1rem;
    }

    .nav-toggle {
        display: flex;
    }

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

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

    .hero-actions {
        justify-content: center;
    }

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

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

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

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

    .courses-filters {
        flex-direction: column;
        align-items: stretch;
    }

    .search-box {
        min-width: auto;
    }

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

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

    .step:not(:last-child)::after {
        display: none;
    }

    .trust-grid {
        grid-template-columns: repeat(2, 1fr);
    }

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

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

    .hero {
        padding: 2rem 0;
    }

    .hero-content h1 {
        font-size: 1.8rem;
    }

    .hero-actions {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

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

    .trust-item {
        flex-direction: column;
        text-align: center;
        gap: 0.5rem;
    }
}

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

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

.spinner {
    border: 2px solid var(--border-color);
    border-top: 2px solid var(--primary-color);
    border-radius: 50%;
    width: 20px;
    height: 20px;
    animation: spin 1s linear infinite;
    display: inline-block;
    margin-right: 0.5rem;
}

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