A while ago I wrote Babble, a toy language to teach myself ANTLR4: https://github.com/nlehuen/babble

It initially supported both English and French keywords: https://github.com/nlehuen/babble/commit/eb090fd3e80238166ac... - that was fun but for some reason I found it cringy and removed it (as if the rest was not cringy either).

Completely off topic, but I also implemented Hodor - "Its main objective is to teach programming to Hodor.": https://github.com/nlehuen/babble/tree/hodor