anchor.diff:    `AppComponent` in a visual tree. 
     A more sophisticated app would have more files and modules, at least as many as it had components.
     
  -  Quickstart isn't sophisticated; one component is all we need.
  +  This Quickstart isn't sophisticated; one component is all we need.
     Yet modules play a fundamental organizational role in even this small app.
     
     Modules rely on other modules. In TypeScript Angular apps, when we need something
  
positive.code:     * We iterate development faster because we only re-compile changed files.
      We notice the difference as soon as the app grows beyond a handful of files.
      
      * pre-compilation fits into a continuous integration process of build, test, deploy.
  :marked
    The `System.import` call tells SystemJS to import the `boot` file 
    (`boot.js` ... after transpiling `boot.ts`, remember?).
  
negative.code: :marked
    ## Appendices
    The balance of this chapter is a set of appendices that
    elaborate on some of the points we covered quickly above.
    
    There is no essential material here. Continued reading is for the curious.
    
  