Below is a hello-world app. See the filesystem tree for how it works.
The type of the hello-world file is app-1, which turns it into an app. Because it is defined on the file itself we don’t need to have an extra .Class file.
There is an .Inline file in it that is executed when the page is loaded. (The page app calls it.) It is of type sjs-2 which stands for Server JavaScript 2, which is v2 of our JavaScript VM. The JS code to be executed is stored in the .Inline file.
There is a .Inline/style.css file responsible for the CSS. The page app applies a namespace on both the CSS file and the HTML generated by .Inline, so that the namespaces match.
The CSS is cached in the browser so that it is fast. Now go change the CSS. As the file changes, the cache will be automatically invalidated (the URL generated by the page app changes).
Please note that this anonymous app is self-contained. You can move/copy it elsewhere and it will still work - which is a big deal.