.a-z {
  ol.index {
    margin-bottom: 1.25em;

    li {
      font-size: 24px;
      display: inline;
      margin-right: 0.6em;

      &:nth-child(-n+13) {
        float: left;
      }

      a {
        font-weight: bold;
        text-decoration: none;
      }

      @media (max-width: 440px) {
        float: left;
      }
    }
  }
}

.a-z {
  ol.index {
    margin-bottom: 1.25em;

    @media (max-width: $mobile-max-width) {
      margin-bottom: govuk-spacing(6);
    }

    li {
      font-size: 24px;
      display: inline;
      margin-right: 0.6em;

      &:nth-child(-n+13) {
        float: left;
      }

      a {
        font-weight: bold;
        text-decoration: none;
      }

      @media (max-width: 440px) {
        float: left;
      }
    }
  }
}

Fix padding between a-z list and selected letter on mobile screen
Fix padding between a-z list and selected letter on mobile screen
