body {
background-color: #f5f7fa;
font-family: 'Microsoft YaHei', sans-serif;
margin: 0;
padding: 0;
display: flex;
justify-content: center;
align-items: center;
min-height: 100vh;
}

.login-container {
width: 100%;
max-width: 400px;
padding: 30px;
background: white;
border-radius: 10px;
box-shadow: 0 5px 15px rgba(0,0,0,0.1);
}

.login-header {
text-align: center;
margin-bottom: 30px;
}

.login-header h2 {
color: #0d47a1;
margin-bottom: 10px;
}

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

.form-group label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: #333;
}

.form-control {
width: 100%;
padding: 10px;
border: 1px solid #ddd;
border-radius: 5px;
font-size: 16px;
box-sizing: border-box;
}

.captcha-container {
display: flex;
gap: 10px;
align-items: center;
}

.captcha-text {
font-family: 'Courier New', monospace;
font-size: 24px;
font-weight: bold;
letter-spacing: 3px;
color: #1e88e5;
background-color: #f5f5f5;
padding: 8px 15px;
border-radius: 5px;
min-width: 60px;
text-align: center;
cursor: pointer;
user-select: none;
}

.btn-refresh {
background-color: #f5f5f5;
border: 1px solid #ddd;
border-radius: 5px;
padding: 8px 12px;
cursor: pointer;
transition: all 0.3s;
}

.btn-refresh:hover {
background-color: #e0e0e0;
}

.btn-login {
width: 100%;
padding: 12px;
background: linear-gradient(135deg, #1e88e5, #0d47a1);
color: white;
border: none;
border-radius: 5px;
font-size: 16px;
cursor: pointer;
transition: all 0.3s;
}

.btn-login:hover {
opacity: 0.9;
}

.error-message {
color: #f44336;
margin-bottom: 20px;
text-align: center;
padding: 10px;
background-color: #ffebee;
border-radius: 5px;
}

footer {
text-align: center;
margin-top: 50px;
padding: 20px;
color: #546e7a;
border-top: 1px solid #e0e0e0;
}