//
// Return line height ( px ) for vertical rhythum
//
// @param   px   font-size
// @param   int  coefficient
// @return  int
//
_vertical-rhythm(font-size, coefficient = 1) {
  between-lines    = _strip-unit(_rem2px(_between-lines));
  base-line-height = _strip-unit(_rem2px(_base-line-height));
  base-font-size   = _strip-unit(_rem2px(_base-font-size));
  font-size        = _strip-unit(font-size);

  line-height = font-size + (between-lines * coefficient);

  if (line-height < font-size + (between-lines * 2)) {
    return _vertical-rhythm(font-size, (coefficient + 1));
  } else {
    if (font-size % base-font-size == 0 && font-size > base-font-size) {
      return line-height - (between-lines / 2);
    }
    return line-height;
  }
}