CSS边框闪烁呼吸样式

<html>
<body>
<head>
.arrow_box{animation: glow 800ms ease-out infinite alternate; }
@keyframes glow {
    0% {
        border-color: #393;
        box-shadow: 0 0 5px rgba(0,255,0,.2), inset 0 0 5px rgba(0,255,0,.1), 0 1px 0 #393;
    }
    100% {
        border-color: #6f6;
        box-shadow: 0 0 20px rgba(0,255,0,.6), inset 0 0 10px rgba(0,255,0,.4), 0 1px 0 #6f6;
    }
}
</head>
<div class="arrow_box"></div>
</body>
</html>