Now that our first Express application is usable, we act on the mantra of this age of software development: mobile-first. Mobile devices, whether they be smartphones, tablet computers, automobile dashboards, refrigerator doors, or bathroom mirrors, are taking over the world. 

Another issue is mobile-first indexing, meaning that search engines are starting to preference indexing the mobile version of a website. Search engines so far concentrated on indexing the desktop version of websites, but the growing popularity of mobile devices means search engine results are skewed away from what folks are using. Google says it is not fair to mobile users if the search result, which was derived from the desktop version, does not match the mobile version of a website. For Google's take, including technical tips on the markup to use, see http://webmasters.googleblog.com/2017/12/getting-your-site-ready-for-mobile.html.

The primary considerations in designing for mobiles are the small screen sizes, the touch-oriented interaction, that there's no mouse, and the somewhat different user interface expectations. With the Notes application, our user interface needs are modest, and the lack of a mouse doesn't make any difference to us. 

In this chapter, we won't do much Node.js development. Instead, we'll:

• Modify the templates for better mobile presentation
• Edit CSS and SASS files to customize the style
• Learn about Bootstrap 4, a popular framework for responsive UI design

By doing so, we'll dip our toes in the water of what it means to be a full stack web engineer.