body {
  font-family: Arial, sans-serif;
  background: linear-gradient(to right, black, red, green);
  color: white;
  animation: fadeIn 1s ease-in-out;
}
form input, form button {
  display: block;
  margin: 10px 0;
  padding: 8px;
}
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}