body {
  background-color: #f8f9fa;
}
.alert-box {
  max-width: 500px;
  margin: 10vh auto 0 auto; /* roughly 1/3 of the screen height */
  padding: 2rem;
  background-color: white;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
  border-radius: 0.5rem;
}
.payment-box {
  max-width: 500px;
  margin: 5vh auto;
  background-color: #fff;
  padding: 2rem;
  border-radius: 10px;
  box-shadow: 0 0 15px rgba(0,0,0,0.05);
}
.qr-img {
  width: 200px;
  height: 200px;
  margin: 0 auto 1rem;
  display: block;
}