```coffeescript
fs = require 'fs'
module.exports = (grunt) ->
	grunt.initConfig
		pkg: grunt.file.readJSON('package.json')
		sass: main:
			files:
				'dist/style.css': 'css/rohpod.scss'
		copy:
			js:
				src: 'js/*.js'
				dest: 'dist/'
				flatten: true
				expand: true
			img:
				src: 'img/*'
				dest: 'dist/'
				flatten: true
				expand: true
			lib:
				src: 'build/jslibs.min.js'
				dest: 'dist/jslibs.min.js'
			index:
				src: 'index.htm'
				dest: 'dist/'
		concat:
			libs:
				src: ['jslib/*.min.js']
				dest: 'build/jslibs.min.js'
		clean:
			dist: 'dist'
			build: 'build'

	grunt.loadNpmTasks 'grunt-contrib-sass'
	grunt.loadNpmTasks 'grunt-contrib-copy'
	grunt.loadNpmTasks 'grunt-contrib-concat'
	grunt.loadNpmTasks 'grunt-contrib-clean'
	grunt.registerTask 'default', () ->
		grunt.task.run ['copy', 'sass']
```

Improve the default build task
user
```coffeescript
fs = require 'fs'
module.exports = (grunt) ->
	grunt.initConfig
		pkg: grunt.file.readJSON('package.json')
		sass: main:
			files:
				'dist/style.css': 'css/rohpod.scss'
		copy:
			js:
				src: 'js/*.js'
				dest: 'dist/'
				flatten: true
				expand: true
			img:
				src: 'img/*'
				dest: 'dist/'
				flatten: true
				expand: true
			lib:
				src: 'build/jslibs.min.js'
				dest: 'dist/jslibs.min.js'
			index:
				src: 'index.htm'
				dest: 'dist/'
		concat:
			libs:
				src: ['jslib/*.min.js']
				dest: 'build/jslibs.min.js'
		clean:
			dist: 'dist'
			build: 'build'

	grunt.loadNpmTasks 'grunt-contrib-sass'
	grunt.loadNpmTasks 'grunt-contrib-copy'
	grunt.loadNpmTasks 'grunt-contrib-concat'
	grunt.loadNpmTasks 'grunt-contrib-clean'
	grunt.registerTask 'default', () ->
		fs.mkdirSync 'build' unless fs.existsSync 'build'
		grunt.task.run 'concat:libs' unless fs.existsSync 'build/jslibs.min.js'
		grunt.task.run [
			'clean:dist'
			'copy'
			# 'sass'
		]
```
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