.loading::after {
  display: inline-block;
  animation: dotty steps(1,end) 1s infinite;
  content: '';
}

@keyframes dotty {
  0%   { content: '\2008\2008\2008'; }
  25%  { content: '.\2008\2008'; }
  50%  { content: '..\2008'; }
  75%  { content: '...'; }
  100% { content: '\2008\2008\2008'; }
}