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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

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

.login-box, .register-box {
    background: white;
    border-radius: 10px;
    padding: 40px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.1);
    max-width: 400px;
    margin: 50px auto;
}

h1, h2, h3 {
    color: #333;
    margin-bottom: 20px;
}

h1 {
    color: white;
}

h2 {
    text-align: center;
    margin-bottom: 30px;
    color: #333;
}

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

label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
    color: #555;
}

input[type="text"],
input[type="password"] {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 16px;
    transition: border-color 0.3s;
}

input[type="text"]:focus,
input[type="password"]:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 2px rgba(102, 126, 234, 0.1);
}

.btn {
    display: inline-block;
    background: #667eea;
    color: white;
    padding: 12px 30px;
    border: none;
    border-radius: 5px;
    font-size: 16px;
    cursor: pointer;
    transition: background 0.3s;
    text-decoration: none;
    text-align: center;
}

.btn:hover {
    background: #5a6fd8;
}

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

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

.btn-logout {
    background: #dc3545;
}

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

.btn-small {
    padding: 8px 15px;
    font-size: 14px;
}

.btn-warning {
    background: #ffc107;
    color: #212529;
}

.btn-danger {
    background: #dc3545;
}

.form-footer {
    text-align: center;
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid #eee;
}

.form-footer a {
    color: #667eea;
    text-decoration: none;
}

.form-footer a:hover {
    text-decoration: underline;
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding: 20px;
    background: rgba(255, 255, 255, 0.9);
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
}

.chat-container {
    background: white;
    border-radius: 10px;
    padding: 30px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.1);
    margin-bottom: 20px;
}

.footer {
    text-align: center;
    color: white;
    padding: 20px;
}

.error-message {
    background: #fee;
    color: #c33;
    padding: 12px;
    border-radius: 5px;
    border: 1px solid #fcc;
    margin-bottom: 20px;
}

.success-message {
    background: #efe;
    color: #3a3;
    padding: 12px;
    border-radius: 5px;
    border: 1px solid #cfc;
    margin-bottom: 20px;
}

.info-box {
    background: #e7f3ff;
    border: 1px solid #b3d9ff;
    border-radius: 5px;
    padding: 15px;
    margin: 20px 0;
}

.demo-info {
    background: #fff8e1;
    border: 1px solid #ffd54f;
    border-radius: 5px;
    padding: 15px;
    margin-bottom: 20px;
}

.info-box h3, .demo-info h3 {
    margin-top: 0;
    color: #0066cc;
}

.info-box ul {
    padding-left: 20px;
    margin: 10px 0;
}

.info-box li {
    margin-bottom: 5px;
}

.text-muted {
    color: #6c757d;
}

small {
    display: block;
    margin-top: 5px;
    color: #666;
    font-size: 0.9em;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .container {
        padding: 10px;
    }
    
    .login-box, .register-box {
        padding: 20px;
        margin: 20px auto;
    }
    
    .header {
        flex-direction: column;
        text-align: center;
        gap: 10px;
    }
    
    .user-info {
        flex-direction: column;
        gap: 10px;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    table {
        display: block;
        overflow-x: auto;
    }
}