dev.js

const fs = require('fs')
    , rollup = require('rollup')
    , commonjs = require('rollup-plugin-commonjs')
    , json = require('rollup-plugin-json')
    , nodeResolve = require('rollup-plugin-node-resolve')
    , stylus = require('stylus')
    , nib = require('nib')
    , wright = require('wright')

wright({
  main: 'src/index.html',
  serve: 'static',
  run: 'm.redraw()',
  debug: true,
  js: {
    watch: 'src/js/**/*.js',
    compile: roll
  },
  css: {
    watch: 'src/css/**/*.styl',
    compile: style
  }
})

function roll() {
  return rollup.rollup({
    entry: 'src/app.js',
    plugins: [
      json(),
      commonjs(),
      nodeResolve()
    ]
  })
  .then(bundle => bundle.generate({ format: 'iife' }).code)
}

function style() {
  return new Promise((resolve, reject) => {
    fs.readFile('src/css/style.styl', 'utf8', (err, str) => {
      if (err)
        return reject(err)

      stylus(str)
      .set('filename', 'src/css/style.styl')
      .use(nib())
      .import('nib')
      .render((err, css) => err ? reject(err) : resolve(css))
    })
  })

}