css3三角形闪烁

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        .box{ animation: change 1s  ease-in  infinite ;  display:block;   width:0; 
    height:0; 
    border-left:10px solid transparent;
    border-right:10px solid transparent;
    border-bottom:10px solid #f00;}
        @keyframes change {
            0%{  opacity:0;}
            50%{  opacity:1;}
            100%{  opacity:0;}
        }
    </style>
</head>
<body>
<a class="box"> </a>
</body>
</html>