@keyframes fadeIn {
  0% { opacity: 0; }
  100% { opacity: 1; }
}
@keyframes snowfall {
  0% { transform: translateY(-10vh); }
  100% { transform: translateY(130vh); }
}
.snowflake {
  background: white;
  border-radius: 50%;
  position: fixed;
  top: -5vh;
  animation: snowfall infinite;
  opacity: 0.1;
}