.box {
  --clr-shadow__border: #5987a3;
  --clr-text: #F6F4EB;
  --clr-rain: #192333;
  --clr-raindrop: #E9F8F9;
  --size: 3rem;
  position: relative;
  outline: 1px solid var(--clr-shadow__border);
}

.button {
  font-weight: 600;
  font-size: 1.5rem;
  background: transparent;
  padding: calc(var(--size) / 3) var(--size);
  border: none;
  cursor: pointer;
  color: var(--clr-text);
  letter-spacing: 0.2rem;
  text-shadow: 2px 0px var(--clr-shadow__border), 0px 2px var(--clr-shadow__border),
  -2px 0px var(--clr-shadow__border), 0px -2px var(--clr-shadow__border);
}

.rain {
  width: 100%;
  height: 100%;
  bottom: 0%;
  gap: 0.6rem;
  z-index: -1;
  opacity: 0;
  transition: 0.5s ease-in-out;
  overflow: hidden;
  position: absolute;
  display: flex;
  background: var(--clr-rain);
}

.box:hover .rain {
  opacity: 1;
}

.raindrop {
  height: 1.4rem;
  min-width: 0.1rem;
  box-shadow: 60px 100px var(--clr-raindrop),-40px -90px var(--clr-raindrop);
  background-color: var(--clr-raindrop);
  animation: rain-animation calc(0.05s * var(--i)) linear infinite;
  opacity: .3;
}

@keyframes rain-animation {
  0% {
    transform: rotate(20deg) translateY(calc(-100% * var(--i)));
  }

  100% {
    transform: rotate(20deg) translateY(calc(100% * var(--i)));
  }
}