#signup_banner
{
  position:fixed;
  bottom: 20px;
  right: 20px;
  width: 200px;
  filter:drop-shadow(2px 2px 3px rgba(0,0,0,.3));
  z-index:100;
}
#signup_banner > img
{
  width:100%;
  height:auto;
}

@media all and (max-width: 767px)
{
  #signup_banner
  {
    	width:min(200px, calc(100% - 200px));
    	left:calc(100% / 2 - min(200px, calc(100% - 200px)) / 2);
  }
}