console 命令行工具 X clear
console
<!DOCTYPE html>
<html>
    <head>
        <style>
            .juxing{
                width:100px;
                height:100px;
                fill:red;
                animation:myfirst 5s infinite backwards;
            }
            @keyframes myfirst{
                0%,100%{ fill:red;}
                50%{fill:blue; width:200px; height:400px;}
             
            }
            </style>
    </head>
    <body>
      <svg>
          <rect x class="juxing"/>
      </svg>
    </body>
</html>