There’s two sides to it, an author creating something using plain text in the authoring tool and a reader viewing the final product. So the author uses plain text to get their point across to the reader.

When you’ve created something you can publish it and the reader can view it at a URL. The author obviously isn’t trying to get a point across to themselves in the app.

The authoring tool is a web app and does quite a lot so it is JS heavy. It works well on mobile but the demo only works in landscape as the mobile version is slimmed down so you do have to rotate your phone.