body {
  background:#1b1a1a;
}

.arrows {
  width: 60px;
  height: 192px;
  position: relative;
  left: 50%;
  margin-left: -30px;
  margin-top: -20px
  bottom: 20px;
}

.arrows path {
  stroke: #2994D1;
  fill: transparent;
  stroke-width: 1px;  
  animation: arrow 2s infinite;
  -webkit-animation: arrow 2s infinite; 
}

@keyframes arrow
{
0% {opacity:0}
40% {opacity:1}
80% {opacity:0}
100% {opacity:0}
}

@-webkit-keyframes arrow /*Safari and Chrome*/
{
0% {opacity:0}
40% {opacity:1}
80% {opacity:0}
100% {opacity:0}
}

.arrows path.a1 {
  animation-delay:-1s;
  -webkit-animation-delay:-1s; /* Safari 和 Chrome */
}

.arrows path.a2 {
  animation-delay:-0.5s;
  -webkit-animation-delay:-0.5s; /* Safari 和 Chrome */
}

.arrows path.a3 { 
  animation-delay:0s;
  -webkit-animation-delay:0s; /* Safari 和 Chrome */
}