<script src='https://combinatronics.io/Figsh/FSCSS/refs/heads/4.0.1/fscss_exec.js' async=""></script>
<button>
  <div class='btn-child'>
    <p class='div-child'></p>
    </div>
  </button>
<style>
  $alter:alternate;
  $inf:infinite;
  
  $(@keyframes big, button, .btn-child, .div-child &[6s linear $inf $alter]){
    0%{ 
      %2(width, height [: 0;])
      }
    100%{
    %2(Height, width[:400px;]) 
      }
   } 
  Button{

    Border: 4px solid;

   } 

  .btn-child{

    Animation-delay: 2s;

    Border: 4px solid #00f;

   } 

 .div-child{

   Animation-delay: 4s;

   Border: 4px solid #f00;

  } 
  </style>