body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    overflow: hidden;
  }
  .rain {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(to bottom, rgba(255,255,255,0.2) 0%, rgba(255,255,255,0) 100%);
    animation: rain 1s infinite linear;
  }
  
  @keyframes rain {
    0% {
      background-position: 0 0;
    }
    100% {
      background-position: 0 100%;
    }
  }