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

body {
    font-family: "Microsoft YaHei", Arial, sans-serif;
    background: #f5f5f5;
}

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

.header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 20px 0;
}

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

.header h1 {
    font-size: 28px;
}

.header nav a {
    color: white;
    text-decoration: none;
    margin-left: 20px;
}

.btn {
    display: inline-block;
    padding: 10px 20px;
    background: #667eea;
    color: white;
    text-decoration: none;
    border-radius: 5px;
    border: none;
    cursor: pointer;
    font-size: 14px;
}

.btn:hover {
    background: #5568d3;
}

.btn-success {
    background: #28a745;
}

.btn-success:hover {
    background: #218838;
}

.btn-danger {
    background: #dc3545;
}

.btn-danger:hover {
    background: #c82333;
}

.btn-sm {
    padding: 5px 10px;
    font-size: 12px;
}

.card {
    background: white;
    border-radius: 10px;
    padding: 20px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    margin-bottom: 20px;
}

.card-title {
    font-size: 20px;
    margin-bottom: 15px;
    color: #333;
}

.form-group {
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    color: #333;
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 14px;
}

.form-group textarea {
    height: 100px;
    resize: vertical;
}

.alert {
    padding: 15px;
    margin-bottom: 20px;
    border-radius: 5px;
}

.alert-success {
    background: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.alert-danger {
    background: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.table {
    width: 100%;
    border-collapse: collapse;
}

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

.table th {
    background: #f8f9fa;
    font-weight: bold;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.course-card {
    background: white;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    transition: transform 0.3s;
}

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

.course-thumbnail {
    width: 100%;
    aspect-ratio: 16 / 9;
    object-fit: cover;
    background: #ddd;
    max-height: 180px;
}

.course-info {
    padding: 15px;
}

.course-title {
    font-size: 18px;
    margin-bottom: 10px;
    color: #333;
}

.course-price {
    font-size: 20px;
    color: #e74c3c;
    font-weight: bold;
}

.footer {
    background: #333;
    color: white;
    text-align: center;
    padding: 30px 0;
    margin-top: 40px;
}