Ask HN: Tell me of your niche languages?

I've been interested in programming languages for a long time, and I know that frequently people post links to their own implementations here.

Have you created your own programming language? Be it a compiler, and interpreter, or a virtual-machine?

If you've not created one of your own are there any niche, small, modern, or new languages you enjoy experimenting with, even if not used in production?

(Not directly related, but if you do have an interest in writing a language I'd highly recommend the "Writing an interpreter in Go" book, by Thorsten Ball. I had fun working through the code, and my own version of the monkey interpreter became pretty advanced https://github.com/skx/monkey/ it also lead to me writing a simple BASIC interpreter https://github.com/skx/gobasic/ - then later still an assembly-language compiler for a calculator.)