I'm a senior software dev and in my spare time I write small apps and libs that nobody uses.
I released TwoFold.js (2✂︎f) stable and I wrote this article about it:
https://crlf.site/log/articles/191121-twofold/
I took me almost 2 months to write, because english is much harder than code 😓

tl;dr;TwoFold is an app that makes plain text files behave like dynamic files. Use-cases include: auto updating documentation, text based dashboards, text virtual assistants, text spreadsheets, turn based games, etc.