code: function coreCss() {
    const buildPath = 'build/css/';
    const core = (name, fonts) => gulp.src([
        (fonts ? '' : '!') + 'core/css/fonts.css',
        'core/css/common.css',
        'core/css/*.css',
      ])
      .pipe($.concat(`${name}.css`))
      .pipe($.insert.prepend(`/*! ${pkg.name} - v${pkg.version} - ${dateformat(new Date(), 'yyyy-mm-dd')} */\n`))
      // Transpile
      .pipe($.autoprefixer({
        browsers: babelrc.presets[0][1].targets.browsers,
        add: true,
        remove: false, // removing prefixes can cause a bug
      }))
      .pipe(gulp.dest(buildPath))
      // Minify
      .pipe($.cssmin({ processImport: false }))
      .pipe($.rename({ suffix: '.min' }))
      .pipe(gulp.dest(buildPath))
    ;
  
    return mergeStream(
      core('onsenui', true),
      core('onsenui-core', false),
  
      gulp.src('core/css/fonts.css')
        .pipe($.rename({ basename: 'onsenui-fonts' }))
        .pipe(gulp.dest(buildPath)),
  
      // font-awesome fle copy
      gulp.src('core/css/font_awesome/**/*')
        .pipe(gulp.dest('build/css/font_awesome/')),
  
      // ionicons file copy
      gulp.src('core/css/ionicons/**/*')
        .pipe(gulp.dest('build/css/ionicons/')),
  
      // material icons file copy
      gulp.src('core/css/material-design-iconic-font/**/*')
      .pipe(gulp.dest('build/css/material-design-iconic-font/'))
    );
  }
docs: ////////////////////////////////////// core-css //////////////////////////////////////