CSS3 擬似要素を使用して、徐々に光る四角形の境界線を実現する方法

<p class="light">
 <img src="http://tva2.sinaimg.cn/crop.0.0.180.180.180/6830a53bjw8f2qo4xzc2zj20500500t0.jpg"/>
 <p class="light-inner">
  <p>前端开发博客</p>
  <p>关注前端开发</p>
 </p>
</p>

.light{
 background: #fff;
 width: 180px;
 height: 180px;
 margin: 100px auto;
 position: relative;
 text-align: center;
 color: #333;
 transform:translate3d(0,0,0);

}
.light-inner{
 padding: 60px 30px 0;
 pointer-events: none;
 position: absolute;
 left: 0;
 top: 0;
 bottom: 0;
 right: 0;
 text-align: center;
 transition: background 0.35s;
 backface-visibility: hidden;
}
.light-inner:before, .light-inner:after{
 display: block;
 content: "";
 position: absolute;
 left: 30px;
 top: 30px;
 right: 30px;
 bottom: 30px;
 border: 1px solid #fff;
 opacity: 0;
 transition: opacity 0.35s, transform 0.35s;
}
.light-inner:before{
 border-left: 0;
 border-right: 0;
 transform:scaleX(0,1);
}
.light-inner:after{
 border-top: 0;
 border-bottom: 0;
 transform: scaleY(1,0);
}
.light:hover .light-inner{
 background: #458fd2
}
.light:hover .light-inner:before, .light:hover .light-inner:after{
 opacity: 1;
 transform: scale3d(1,1,1);
}

.light-inner p{
 transition: opacity .35s, transform 0.35s;
 transform: translate3d(0,20px,0);
 color: #fff;
 opacity: 0;
 line-height: 30px;
}
.light:hover .light-inner p{
 transform: translate3d(0,0,0);
 opacity: 1;
}