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

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    margin-bottom: 1rem;
}

h1 {
    font-size: 2.5rem;
}

h2 {
    font-size: 2rem;
}

h3 {
    font-size: 1.5rem;
}

p {
    margin-bottom: 1rem;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 12px 24px;
    background-color: #007bff;
    color: white;
    text-decoration: none;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 500;
    transition: background-color 0.2s ease;
    text-align: center;
}

.btn:hover {
    background-color: #0056b3;
}

.btn-secondary {
    background-color: #6c757d;
}

.btn-secondary:hover {
    background-color: #545b62;
}

.btn-outline {
    background-color: transparent;
    color: #007bff;
    border: 2px solid #007bff;
}

.btn-outline:hover {
    background-color: #007bff;
    color: white;
}

/* Cards */
.card {
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    padding: 24px;
    margin-bottom: 24px;
}

.lecture-card {
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    padding: 24px;
    text-align: center;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.lecture-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

/* Navigation */
.nav {
    background: white;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.logo {
    text-decoration: none;
    color: #333;
}

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

.nav-links a {
    text-decoration: none;
    color: #333;
    font-weight: 500;
    transition: color 0.2s ease;
    padding: 8px 0;
    display: inline-flex; /* keep same vertical alignment as buttons */
    align-items: center;
    line-height: 1;
}

.nav-links a:hover,
.nav-links a.active {
    color: #007bff;
}

.nav-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

/* Language Switcher */
.language-switcher {
    display: flex;
    gap: 0.5rem;
}

.lang-btn {
    padding: 6px 12px;
    border: 1px solid #ddd;
    background: white;
    cursor: pointer;
    border-radius: 4px;
    font-size: 14px;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
    line-height: 1;
}

.lang-btn.active {
    background: #007bff;
    color: white;
    border-color: #007bff;
}

.lang-btn:hover:not(.active) {
    background: #f8f9fa;
}

/* Cart */
.cart-icon {
    position: relative;
    text-decoration: none;
    color: #333;
    font-size: 1.5rem;
    transition: color 0.2s ease;
    display: inline-flex;
    align-items: center;
    line-height: 1;
}

.cart-icon:hover {
    color: #007bff;
}

.cart-badge {
    position: absolute;
    top: -8px;
    right: -8px;
    background: #dc3545;
    color: white;
    border-radius: 50%;
    width: 20px;
    height: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: bold;
}

.cart-badge.hidden {
    display: none;
}

/* Main Content */
.main-content {
    min-height: calc(100vh - 80px);
    padding: 2rem 0;
}

/* Welcome Section */
.welcome-section {
    text-align: center;
    margin-bottom: 4rem;
}

.welcome-subtitle {
    font-size: 1.2rem;
    color: #666;
    margin-bottom: 2rem;
}

/* Lectures Section */
.lectures-section h2 {
    text-align: center;
    margin-bottom: 2rem;
}

.lectures-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

/* Lecture Pages */
.lecture-content {
    max-width: 800px;
    margin: 0 auto;
}

.lecture-navigation {
    display: flex;
    justify-content: space-between;
    margin-top: 2rem;
}

.code-block {
    background: #f8f9fa;
    padding: 1rem;
    border-radius: 4px;
    overflow: auto;
    white-space: pre-wrap;
    font-family: 'Courier New', monospace;
    margin: 1rem 0;
}

/* Tables */
.data-table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
    border: 1px solid #ddd;
}

.data-table th,
.data-table td {
    border: 1px solid #ddd;
    padding: 12px;
    text-align: left;
}

.data-table th {
    background-color: #f8f9fa;
    font-weight: 600;
    color: #333;
}

.data-table tbody tr:nth-child(even) {
    background-color: #f8f9fa;
}

.data-table tbody tr:hover {
    background-color: #e9ecef;
}

/* Notes */
.note {
    margin-top: 1rem;
    padding: 0.75rem 1rem;
    background-color: #fff3cd;
    border-left: 4px solid #ffc107;
    border-radius: 4px;
    font-size: 0.9rem;
    color: #856404;
}

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

.product-card {
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    padding: 0;
    overflow: hidden;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.product-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

.product-image {
    width: 100%;
    height: 250px;
    object-fit: cover;
}

.product-info {
    padding: 1.5rem;
    text-align: center;
}

.product-price {
    font-size: 1.2rem;
    color: #007bff;
    font-weight: bold;
    margin: 1rem 0;
}

.product-sizes {
    font-size: 0.9rem;
    color: #666;
    margin-bottom: 1rem;
}

/* Cart */
.cart-container {
    display: grid;
    grid-template-columns: 1fr 400px;
    gap: 2rem;
}

.cart-item {
    display: flex;
    gap: 1rem;
    align-items: center;
    padding: 1rem;
    border-bottom: 1px solid #eee;
}

.cart-item-image {
    width: 80px;
    height: 80px;
    object-fit: cover;
    border-radius: 4px;
}

.cart-item-info {
    flex: 1;
}

.cart-item-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.quantity-input {
    width: 60px;
    padding: 4px;
    border: 1px solid #ddd;
    border-radius: 4px;
    text-align: center;
}

.cart-summary {
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    padding: 1.5rem;
    height: fit-content;
}

.cart-empty {
    text-align: center;
    padding: 3rem;
}

/* Checkout Form */
.checkout-form {
    max-width: 500px;
    margin: 0 auto;
}

.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 8px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 16px;
}

.form-group textarea {
    resize: vertical;
    min-height: 80px;
}

.form-actions {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal.show {
    display: flex;
}

.modal-content {
    background: white;
    border-radius: 8px;
    padding: 2rem;
    max-width: 500px;
    width: 90%;
    max-height: 90vh;
    overflow: auto;
}

/* Success Message */
.success-message {
    text-align: center;
    padding: 1.5rem 1rem 2rem;
}

.success-message h2 {
    color: #28a745;
    margin-bottom: 1rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-container {
        flex-direction: column;
        gap: 1rem;
    }
    
    .nav-links {
        gap: 1rem;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
    
    .cart-container {
        grid-template-columns: 1fr;
    }
    
    .lecture-navigation {
        flex-direction: column;
        gap: 1rem;
    }
    
    .form-actions {
        flex-direction: column;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }
    
    .lectures-grid {
        grid-template-columns: 1fr;
    }
    
    .shop-grid {
        grid-template-columns: 1fr;
    }
}