@mixin base--a($color: null, $background: null) {

  color: color('gray', 90);
  border-bottom: 2px solid color('gray', 90);
  font-weight: 400;
  text-decoration: none;
  transition: 0.2s;
  cursor: pointer;

  &:visited {
    color: color('gray', 90);
    border-bottom: 2px solid color('gray', 90);
  }

  &:hover,
  &:focus {
    color: color('purple', 50);
    border-bottom: 2px solid color('purple', 50);
  }
}