function styles() {
  return src("scss/style.scss")
    .pipe(eval(preprocessor)())
    .pipe(concat("style.css"))
    .pipe(
      autoprefixer({ overrideBrowserslist: ["last 10 versions"], grid: true })
    )
    .pipe(
      cleancss({
        level: { 1: { specialComments: 0 } } /* , format: 'beautify' */,
      })
    )
    .pipe(dest("./"))
    .pipe(browserSync.stream());
}