body {
  background-color: #f8f9fa;
}

.container {
  max-width: 800px;
}

.card {
  border-radius: 8px;
}

.btn-primary {
  background-color: #007bff;
  border: none;
}

.btn-primary:hover {
  background-color: #0056b3;
}

.form-control {
  border-radius: 6px;
}

.student-qr-panel[hidden] {
  display: none !important;
}

.student-qr {
  width: min(360px, 80vw);
  height: min(360px, 80vw);
  background: #fff;
  padding: 12px;
  border-radius: 8px;
}

.student-qr img,
.student-qr canvas {
  width: 100% !important;
  height: 100% !important;
}

@media (max-width: 576px) {
  .container {
    padding: 15px;
  }

  h2 {
    font-size: 1.5rem;
  }

  .card-title {
    font-size: 1.25rem;
  }
}