.flash {
  position: fixed;
  top: 20px;
  left: 50%;
  transform: translateX(-50%);
  padding: 10px 20px;
  border-radius: 5px;
  animation: fade-out 5s forwards;
}

.flash-notice { background-color: #d4edda; }
.flash-alert { background-color: #f8d7da; }

@keyframes fade-out {
  0% { opacity: 1; }
  90% { opacity: 1; }
  100% { opacity: 0; }
}