.arrows {
    width: 60px;
    height: 72px;
    position: absolute;
    left: 50%;
    margin-left: -30px;
    top: 46vw ;
}

.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 */
}