@mixin gridparent($columns) {
  @extend %#{$columns};
  @include whitespacefix;
  @include nogutters;
}

@mixin griditem($columns, $font_size) {
  @extend %#{$columns};
  @extend %#{$font_size};
  @include inlineblock;
}

.posts {
  @include gridparent(c4);

  .post {
    @include griditem(c2, regular);
  }
}