body {
  /* 漸變背景 */
  background: linear-gradient(135deg, #f3f4f6, #8b8f96);
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  margin: 0;
}
.card {
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(10px);
  border-radius: 16px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}
.card-header {
    color: #111827;
    border-top-left-radius: 15px;
    border-top-right-radius: 15px;
    padding: 1.5rem;
    font-size: 1.5rem;
    font-weight: bold;
}
.form-label {
    font-weight: 600;
    color: #374151;
}
/*.form-control {
    border-radius: 8px; 
    padding: 0.75rem 1rem;
    border: 1px solid #ddd;
}
.form-control:focus {
    border-color: #b4b4b4;
    box-shadow: 0 0 0 0.25rem rgba(34, 34, 34, 0.25);
}*/
.form-control {
  border-radius: 10px;
  border: 1px solid #d1d5db;
  padding: 0.75rem 1rem;
  transition: border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
  background-color: #ffffff;
  color: #111827;
}
.form-control:focus {
  border-color: #6b7280;
  box-shadow: 0 0 4px rgba(107, 114, 128, 0.25);
}

/*
  Meng:不要用bootstrap預設名稱命名，我先註解起來，並且找到這個樣式後，修改class內容，並且open註解
*/
.btn-primary-login {
  background: linear-gradient(135deg, #374151, #111827);
  border: none;
  border-radius: 10px;
  font-weight: 700;
  color: #f3f4f6;
  transition: transform 0.15s ease, box-shadow 0.25s ease, filter 0.2s ease;
}
.btn-primary-login:hover {
  transform: translateY(0);
  filter: brightness(0.98);
}
.spinner-border {
  width: 1.5rem;
  height: 1.5rem;
}
.hidden {
  display: none;
}

/*.alert-danger {
    border-radius: 8px;
    font-size: 0.9rem;
    padding: 0.75rem 1rem;
}*/

.alert-danger {
  border-radius: 10px;
  font-size: 0.95rem;
  padding: 0.75rem 1rem;
  border: none;
  background: rgba(220, 53, 69, 0.08);
  color: #570e0e;
}

.hr-center {
  margin: 8px auto;
  width: 50%;
  height: 0;
  border: 0;
  border-top: 6px solid #9ca3af;
  border-radius: 3px;
}