In any programming language it's an interesting challenge to fit an entire functional program into under 140 characters.
APL: challenge accepted
https://aplwiki.com/wiki/Conway's_Game_of_Life
A quick search has not found any implementations of an APL-family language on the 2600, so let this comment be an inspiration for one of you madlads out there to actually do it. The 2600 has only 128B of RAM, but a lot of consoles around this era had additional bankswitched RAM on the cartridges.
If you don't want to start completely from scratch, may I recommend you take a look at the VideoBrain? https://en.wikipedia.org/wiki/VideoBrain_Family_Computer (only language ever available for it was APL/S -- "structured" APL.)
Also, the "Decker" Hypercard-alike has a K-inspired language that is pretty nice. (Yes, much more modern, but still feels a bit like something "of that era".)