jekyll-theme-nostalgia

The original "plain" HTML theme, in Jekyll.

The plain theme is formatted like this:

* {
  font-family: serif
  background-colour: white
}

Why does it function?

Well, the story begins with Cascading Style Sheets (CSS), currently CSS3. CSS is not a programming language nor HTML, but therefore while JavaScript is a programming language, you actually use JS to program HTML.

So, Jekyll would work with the plain style, meaning you can format plain HTML using Markdown. An example is at the Github Pages website.