.ls {
  letter-spacing: rem($type-scale * 0.1);
}

.ls-n {
  letter-spacing: rem($type-scale * -0.05);
}

@each $breakpoint-name, $breakpoint-value in $breakpoints {
  @media #{$breakpoint-value} {
    .#{$breakpoint-name}--ls {
      letter-spacing: rem($type-scale * 0.1);
    }

    .#{$breakpoint-name}--ls-n {
      letter-spacing: rem($type-scale * -0.05);
    }
  }
}