npm dash -v (check node.js version)
npm install -g gulp (global install gulp to the system)


Project folder:

npm init
npm install gulp --save-dev
npm install gulp-less --save-dev
npm install gulp-concat-css --save-dev
npm install gulp-csso --save-dev
npm install gulp-plumber --save-dev
npm install gulp-browser-sync --save-dev




var gulp = require('gulp'), 				//gulp init
	less = require('gulp-less'),			//less init
	concatCSS = require('gulp-concat-css'), //concat plugin init
	minify = require('gulp-csso'),			//plugin init
	plumber = require('gulp-plumber');		//plumber init
	bs = require('browser-sync');			//bs init

gulp.task('default', function() {			//default - taskName
	bs.init({								//browser-sync init
		server: {
			baseDir: "app/",				// what folder bs must to watch
			//proxy: "homework.sl" 			// thats for bs+openserver
		},
		notify: false
	});
	gulp.watch("app/less/*.less", ['less']);			//if we edit any .less file, then 'less' task starts
    gulp.watch("app/*.html").on('change', bs.reload);	//if we edit any.html file, then bs reloads

})

gulp.task('less', function() {				//new task. less - taskName
	return gulp.src('app/less/*.less')		//take all .less files from app/less/
		  .pipe(plumber())
          .pipe(less())						//less compile
          .pipe(concatCSS('style.css'))		//less files concating to style.css
          .pipe(minify())					//minifying css file w/ plugin "gulp-csso" (#4 line)
          .pipe(gulp.dest('app/css/')) 		//putting to new folder in dist/styles/
          .pipe(bs.stream());				// just use it after gulp.dest()
});