body {
  font-family: "Segoe UI", Arial, sans-serif;
  background: #f5f5f5;
  display: flex;
  height: 100vh;
  justify-content: center;
  align-items: center;
  margin: 0;
}

.login-box {
  background: #fff;
  padding: 28px 22px;
  border-radius: 10px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  width: 100%;
  max-width: 340px;
  box-sizing: border-box;
}

.login-box h2 {
  margin-bottom: 20px;
  text-align: center;
  color: #333;
  font-size: 1.2rem;
}

.form-group {
  margin-bottom: 16px;
}

input[type="text"],
input[type="password"] {
  width: 100%;
  padding: 12px;
  font-size: 14px;
  border: 1px solid #ccc;
  border-radius: 6px;
  box-sizing: border-box;
}

button {
  width: 100%;
  padding: 12px;
  font-size: 15px;
  background: #007bff;
  color: white;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.3s;
}

button:hover {
  background: #0056b3;
}

.error {
  color: #d9534f;
  margin-top: 15px;
  text-align: center;
  font-weight: bold;
  font-size: 14px;
}

/* ✅ 手机端优化 */
@media (max-width: 480px) {
  .login-box {
    margin: 0 14px;
    padding: 22px 16px;
  }
  .login-box h2 {
    font-size: 1rem;
  }
  input[type="text"],
  input[type="password"] {
    font-size: 13px;
    padding: 10px;
  }
  button {
    font-size: 14px;
    padding: 10px;
  }
}