@include breakpoint($mobile-breakpoint) {
  body {
    &.nav-open {
      right: percentage(2/3);
    }
  }
}

@include breakpoint($mobile-and-tablet-breakpoint) {
  body {
    // layout
    right: 0;

    // styling
    @include transition(right 0.2s ease-in-out);
  }
}

@include breakpoint($tablet-breakpoint) {
  body {
    &.nav-open {
      right: percentage(1/2);
    }
  }
}