.btn{
    position:relative; 
    ...
    transition: all .3s;
    
    &:active,
    &:focus{
       outline:none; 
       transform:translateY(-.1rem);
       @include shadow-light;
       
       &:after{      //qui il problema!!! almeno credo *******************
          transform:scaleX(1.4) scaleY(1.6);
          opacity:1;
       }
    }
    
    &--gold{
        background-color:darkgoldenrod;
        color:white;
        border:2px solid goldenrod;

         &:hover{
             background-color:white;
             color:darkgoldenrod;
             border:2px solid goldenrod;
         }

         &::after{
             background-color:#efefe7;
         }
    }


  &::after {
    content:"";
    display:inline-block;
    height:100%;
    width:100%;
    position:absolute;
    top:0;
    left:0;
    z-index:-1;
    opacity:0;
    transition:all .3s;
  }