Frustratingly I saw a fun-looking language posted here before, which was a virtual-machine based system. It was small, clear, and had a good range of libraries and I'm damned if I can find it again!
Were either of these two the ones you were thinking of?
https://pharo.org/ - A language with an IDE
http://pixielang.org/ - A lisp.
Sadly not a match. All I remember was that the language was written in C, compiled to bytecode and was executed in a virtual machine (like Lua, and similar languages). It was "small" and "fast" and probably had a C-like syntax.
I should perform a decent search, because the more I think about it the more I'm annoyed now!
I should just post an "Ask HN: Tell me of your niche languages" and hope I get lucky!