I love this. My very own static site generator, Teeny [1], is going on five years now. It's 350 lines of hand-written JS and has powered all my blogs and personal websites for years. It currently powers https://yakko.dev.
I added plugins this year which made it really powerful and allows me to keep the core small.
Markdown to html was a fun project. I wrote a tool like pandoc, with far fewer features, for school about 10 years ago.
I needed pandoc, but the internet and electricity were both out, so I built my own in a race against my dying ebay laptop battery.