.show {
  opacity: 1;
  visibility: visible;
}

.scroll_down {
  opacity: 1;
  margin: 0;
  padding: 0;
  height: 100px;
  width: 100px;
  visibility: visible;
  position: absolute;
  cursor: pointer;
  display: block;
  border: none;
  right: calc(50% - 50px);
  bottom: 25px;
  outline: 0;
  background-color: transparent;
  background-image: url("../machines/scroll_down.png");
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
  z-index: 9;
  -webkit-transition: all 0.1s ease-in-out;
  transition: all 0.1s ease-in-out;
}

.not-show {
  opacity: 0;
  visibility: hidden;
}

@-webkit-keyframes down_bounce {
  0%,
  100% {
    -webkit-transform: translateY(0);
  }

  50% {
    -webkit-transform: translateY(20px);
  }
}

@keyframes down_bounce {
  0%,
  100% {
    transform: translateY(0);
  }

  50% {
    transform: translateY(20px);
  }
}

.down_fade {
  opacity: 1;

  /* -webkit-animation: fadein_2 2s  4s 1 forwards; 
     -ms-animation: fadein 2s  4s 1 forwards; 
      -o-animation: fadein 2s  4s 1 forwards; 
         animation: fadein 2s  4s 1 forwards; */
  animation: down_bounce 2.5s ease-in-out infinite both,
    fadein_2 2s 1s 1 forwards;
}