css3帮助文档哪位大神有？

<style>.gridList li .btn:before,.gridList li .btn:after { content: ''; position: absolute; bottom: -3px; width: 0.9vw; height: 1px; background: #1D1D1B; transition: transform .3s linear;}.gridList li .btn:before { right: 50%; transform-origin: left center;}.gridList li .btn:after { left: 49.8%; transform-origin: right center;}.gridList li:hover .btn:before { transform: rotate(30deg) scaleX(1.155);}.gridList li:hover .btn:after { transform: rotate(-30deg) scaleX(1.155);}</style><li class="opened" style="color:#fff;background: #000f9f"><a class="btn" href="javascript:;"><span>More</span></a></li>
这是一个css3的箭头动画效果
参考链接地址：https://www.yimumu.com/idea/8.html