gulpfile.js

var gulp = require('gulp')
var browserSync = require('browser-sync')
var sass = require('gulp-sass')
var prefix = require('gulp-autoprefixer')

gulp.task('serve', ['sass'], function () {
  browserSync.init({
    server: {
      baseDir: './'
    },
    open: false,
    online: false,
    notify: false
  })

  gulp.watch('scss/*.scss', ['sass'])
  gulp.watch(['**/*.html', 'js/*', 'shaders/*']).on('change', browserSync.reload)
})

gulp.task('sass', function () {
  return gulp.src('scss/*.scss')
    .pipe(sass({
      outputStyle: 'expanded',
      includePaths: ['scss']
    }))
    .pipe(prefix(['last 5 versions'], { cascade: true }))
    .pipe(gulp.dest('css'))
    .pipe(browserSync.reload({ stream: true }))
})

gulp.task('default', ['serve'])