<!DOCTYPE html>
<html><head><meta charset="utf-8"><title></title><style>.box{width:300px;height: 200px;border: 1px solid red;/* 表示永远的旋转 */animation: myAnimal 5s infinite;}/* 定义一个动画 */@keyframes myAnimal{from{background-color: #228B22;width:300px;height: 200px;border-radius: 1px;}to{background-color: #228B22;width:500px;height: 400px;border-radius: 50%;}}</style></head><body><div class="box"></div></body>
</html>