body {
  background: #f5f5f5;
  font-family: sans-serif;
}
.login-container {
  width: 320px;
  margin: 100px auto;
  padding: 30px;
  background: #fff;
  border-radius: 4px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}
.login-container h2 {
  margin-bottom: 20px;
  text-align: center;
}
.form-group { margin-bottom: 15px; }
.form-group label { display: block; margin-bottom: 5px; }
.form-group input {
  width: 100%;
  padding: 8px;
  box-sizing: border-box;
}
button {
  width: 100%;
  padding: 10px;
  border: none;
  background: #1890ff;
  color: #fff;
  cursor: pointer;
  border-radius: 2px;
}
button:hover { background: #40a9ff; }
.error {
  color: #f00;
  margin-top: 10px;
  text-align: center;
}