.arrow {
  position: absolute;
  width: 0;
  height: 0;
  border-left: 10px solid transparent;
  border-right: 10px solid transparent;
  border-bottom: 15px solid #ff0000eb; /* Red */
  opacity: 0;
  transition: opacity 0.5s ease-in-out;
}

.show-arrow {
  opacity: 1;
}