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

body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f4f4f4;
}

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

header {
    background-color: #2c3e50;
    color: white;
    padding: 20px;
    border-radius: 5px;
    margin-bottom: 20px;
}

header h1 {
    margin-bottom: 10px;
}

.btn-back {
    display: inline-block;
    color: white;
    text-decoration: none;
    padding: 8px 15px;
    background-color: #34495e;
    border-radius: 3px;
    font-size: 14px;
}

.btn-back:hover {
    background-color: #455a64;
}

.message {
    background-color: #4caf50;
    color: white;
    padding: 10px;
    border-radius: 5px;
    margin-bottom: 20px;
}

section {
    background-color: white;
    padding: 20px;
    border-radius: 5px;
    margin-bottom: 20px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

section h2 {
    margin-bottom: 15px;
    color: #2c3e50;
    border-bottom: 2px solid #3498db;
    padding-bottom: 10px;
}

.form-row {
    display: flex;
    gap: 10px;
    margin-bottom: 10px;
}

.form-row input {
    flex: 1;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 3px;
    font-size: 14px;
}

.form-row button {
    padding: 10px 20px;
    background-color: #3498db;
    color: white;
    border: none;
    border-radius: 3px;
    cursor: pointer;
    font-size: 14px;
}

.form-row button:hover {
    background-color: #2980b9;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
}

table thead {
    background-color: #34495e;
    color: white;
}

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

table tbody tr:hover {
    background-color: #f9f9f9;
}

table tbody tr:last-child td {
    border-bottom: none;
}

.grade {
    font-weight: bold;
    color: #27ae60;
}

.btn {
    display: inline-block;
    padding: 6px 12px;
    text-decoration: none;
    border-radius: 3px;
    font-size: 13px;
    border: none;
    cursor: pointer;
    margin-right: 5px;
}

.btn-view {
    background-color: #3498db;
    color: white;
}

.btn-view:hover {
    background-color: #2980b9;
}

.btn-delete {
    background-color: #e74c3c;
    color: white;
}

.btn-delete:hover {
    background-color: #c0392b;
}

.empty-state {
    text-align: center;
    padding: 40px;
    color: #7f8c8d;
}

.empty-state p {
    font-size: 16px;
}

@media (max-width: 768px) {
    .form-row {
        flex-direction: column;
    }
    
    table {
        font-size: 12px;
    }
    
    table th, table td {
        padding: 8px;
    }
}