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

body {
    font-family: Arial, sans-serif;
    background: #f4f4f4;
}

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

.header {
    background: #2c3e50;
    color: white;
    padding: 20px;
    text-align: center;
}

.nav {
    background: #34495e;
    padding: 10px;
}

.nav a {
    color: white;
    padding: 10px 20px;
    text-decoration: none;
    display: inline-block;
}

.nav a:hover {
    background: #2c3e50;
}

.login-form, .form-container {
    background: white;
    max-width: 400px;
    margin: 50px auto;
    padding: 30px;
    border-radius: 5px;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
}

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

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}

.form-group input, .form-group textarea, .form-group select {
    width: 100%;
    padding: 8px;
    border: 1px solid #ddd;
    border-radius: 3px;
}

button, .btn {
    background: #3498db;
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 3px;
    cursor: pointer;
}

button:hover, .btn:hover {
    background: #2980b9;
}

.course-grid, .video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.course-card, .video-card {
    background: white;
    padding: 20px;
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.video-container {
    background: white;
    padding: 20px;
    border-radius: 5px;
    margin-bottom: 20px;
}

.video-player {
    width: 100%;
    min-height: 400px;
    background: black;
}

.comment-section {
    background: white;
    padding: 20px;
    border-radius: 5px;
    margin-top: 20px;
}

.comment {
    border-bottom: 1px solid #ddd;
    padding: 10px;
    margin-bottom: 10px;
}

.admin-reply {
    background: #f0f0f0;
    padding: 10px;
    margin-top: 10px;
    margin-left: 20px;
    border-left: 3px solid #3498db;
}

.success {
    color: green;
    padding: 10px;
    background: #d4edda;
    border-radius: 3px;
    margin-bottom: 10px;
}

.error {
    color: red;
    padding: 10px;
    background: #f8d7da;
    border-radius: 3px;
    margin-bottom: 10px;
}

table {
    width: 100%;
    background: white;
    border-collapse: collapse;
}

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

table th {
    background: #34495e;
    color: white;
}

.stats {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: white;
    padding: 20px;
    border-radius: 5px;
    text-align: center;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.stat-number {
    font-size: 36px;
    font-weight: bold;
    color: #3498db;
}

.complete-btn {
    background: #27ae60;
    margin-top: 20px;
}

.complete-btn:disabled {
    background: #95a5a6;
    cursor: not-allowed;
}