Bliz is incredibly easy, interpolated server-side scripting for Gemini. I created Bliz, and it powers this site.
In short, write plain text files as normal, but insert scripts in the middle of them.
Highlighting for Bliz/Gemtext.
If you're not sure how to use this, try saving bliz.el into ~/.emacs.d/, then add the following code snippet somewhere in ~/.emacs:
(load (expand-file-name "~/.emacs.d/bliz.el"))