.back-to-top-button {
  $block: #{&};

  @include position(fixed, auto, $whitespace-9, $whitespace-9);

  /* stylelint-disable-next-line @morev/bem/no-block-properties 
  -- Button must overflow all other elements */
  z-index: 999;
  box-shadow: get-shadow(medium, $color-neutral-1);
}