Germinate is an ultra-minimal browser for the Gemini protocol, a lightweight alternative to the World Wide Web.
It's written in a literate programming style using Racket, so the source code is hopefully a good introduction to the Gemini protocol itself.
To run the browser, you can use a binary distribution from the releases page or run the code in DrRacket.
The Gemini home page
Viewing results in Gus, the Gemini search engine