#showBtn {
  width: 30px;
  height: 40px;
  position: relative;
}

#showBtn span {
  width: 100%;
  height: 0px;
  border: 2px solid #677;
  background-color: #677;
  border-radius: 10px;
  display: block;
  position: absolute;
  transform: translate(-50%, -50%);
  left: 50%;
  transition: .15s ease-in-out;
  box-shadow: 0 0 1px #fff;
}

#showBtn span:nth-child(1) {
  top: 25%;
}

#showBtn span:nth-child(2) {
  top: 50%;
}

#showBtn span:nth-child(3) {
  top: 50%;
}

#showBtn span:nth-child(4) {
  top: 75%;
}

.opacityN {
  opacity: 0;
}

.opacityB {
  opacity: 1;
}