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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
}

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

header {
    background: white;
    padding: 20px;
    border-radius: 10px;
    margin-bottom: 20px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header h1 {
    color: #333;
    font-size: 28px;
}

.card {
    background: white;
    padding: 30px;
    border-radius: 10px;
    margin-bottom: 20px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.card h2 {
    color: #333;
    margin-bottom: 20px;
    font-size: 24px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    color: #555;
    font-weight: 500;
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 12px;
    border: 2px solid #e0e0e0;
    border-radius: 6px;
    font-size: 16px;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: #667eea;
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 6px;
    font-size: 16px;
    cursor: pointer;
    transition: all 0.3s;
    font-weight: 500;
}

.btn-primary {
    background: #667eea;
    color: white;
}

.btn-primary:hover {
    background: #5568d3;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(102, 126, 234, 0.4);
}

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

.btn-secondary:hover {
    background: #5a6268;
}

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

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

.btn-danger {
    background: #dc3545;
    color: white;
}

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

.btn-large {
    width: 100%;
    padding: 16px;
    font-size: 18px;
}

.button-group {
    display: flex;
    gap: 10px;
    margin-top: 20px;
}

.button-group a,
.button-group button {
    flex: 1;
    text-align: center;
    text-decoration: none;
}

.filter-bar {
    margin-bottom: 20px;
    display: flex;
    gap: 10px;
}

.class-item {
    border: 2px solid #e0e0e0;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 15px;
    transition: all 0.3s;
}

.class-item:hover {
    border-color: #667eea;
    box-shadow: 0 2px 8px rgba(102, 126, 234, 0.2);
}

.class-item h3 {
    color: #333;
    margin-bottom: 10px;
}

.class-item p {
    color: #666;
    margin-bottom: 8px;
}

.class-item .status {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 14px;
    font-weight: 500;
}

.status.active {
    background: #d4edda;
    color: #155724;
}

.status.ended {
    background: #f8d7da;
    color: #721c24;
}

.class-actions {
    margin-top: 15px;
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.class-actions button {
    padding: 8px 16px;
    font-size: 14px;
}

.message {
    padding: 15px;
    border-radius: 6px;
    margin-top: 20px;
    font-weight: 500;
}

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

.message.error {
    background: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.class-info {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 30px;
}

.class-info h2 {
    color: #667eea;
    margin-bottom: 10px;
}

.class-info p {
    color: #666;
}

.leave-form-item {
    border: 1px solid #e0e0e0;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 15px;
}

.leave-form-item h3 {
    color: #333;
    margin-bottom: 10px;
}

.leave-form-item .info {
    color: #666;
    margin-bottom: 8px;
}

.leave-form-item .actions {
    margin-top: 15px;
    display: flex;
    gap: 10px;
}

.leave-form-item img {
    max-width: 100%;
    margin-top: 15px;
    border-radius: 8px;
    border: 2px solid #e0e0e0;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
}

table th,
table td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #e0e0e0;
}

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

table tr:hover {
    background: #f8f9fa;
}

/* 模态框样式 */
.modal {
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, 0.5);
}

.modal-content {
    background-color: #fefefe;
    margin: 5% auto;
    padding: 30px;
    border-radius: 10px;
    width: 90%;
    max-width: 800px;
    max-height: 80vh;
    overflow-y: auto;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.modal-content h2 {
    color: #333;
    margin-bottom: 20px;
}

.modal-content h3 {
    color: #555;
    margin-bottom: 15px;
    font-size: 18px;
}

.close {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    line-height: 20px;
}

.close:hover,
.close:focus {
    color: #000;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 14px;
}

.btn-warning {
    background: #ffc107;
    color: #000;
}

.btn-warning:hover {
    background: #e0a800;
}

@media (max-width: 768px) {
    .container {
        padding: 10px;
    }

    header {
        flex-direction: column;
        text-align: center;
    }

    header h1 {
        font-size: 22px;
        margin-bottom: 10px;
    }

    .card {
        padding: 20px;
    }

    .button-group {
        flex-direction: column;
    }

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

    .class-actions button {
        width: 100%;
    }

    .modal-content {
        width: 95%;
        margin: 10% auto;
        padding: 20px;
    }
}