a link is not working in sass code example

Example: scss link style

$fade-white : #eee;
$white : #ccc;

a{
  color: $fade-white;
  text-decoration: none;

  &:visited{
    color: $white;
    text-decoration: none;
    opacity: 0.42;
  }
  &:hover{
    opacity: 0.7;
    text-decoration: underline;
  }
  &:active{
    opacity: 1;
    text-decoration: none;
  }
}