@keyframes snow {
  0% {
    fill-opacity: 1;
  }
  100% {
    fill-opacity: 0;
    transform: translateY(70%);
  }
}

.snow {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  .particle {
    fill: #fff;
    animation: snow 6s ease-out infinite;
    &:nth-child(2n) {
      animation-delay: 1s;
    }
    &:nth-child(3n) {
      animation-delay: 3.5s;
      animation-duration: 6.3s;
    }
    &:nth-child(4n) {
      animation-delay: 2s;
      animation-duration: 6.2s;
    }
    &:nth-child(5n) {
      animation-delay: 4s;
    }
  }
}