.gadget{
  position:relative;
}

.pioggia {
  position:absolute;
  left:0;
  top:0;
  width:100%;
  height:100%;
  pointer-events:none;
}

.brillantino{
  position:absolute;
  top:-40px;
  animation: caduta linear infinite;
  animation-duration: calc(5s + var(--i) * 0.5s);
  animation-delay: calc(var(--i) * 0.5s);
}

@keyframes caduta{
  from { transform: translateY(-40px); }
  to { transform: translateY(320px); }
}