If you want a Lispier robot programming game, check out GNU Robots. You use the dialect of Scheme that most GNU tools are extensible with, so you'll get something out of it!
there is also screeps if anyone wants the MMO experience.
but this one aint free though, because you're effectively running code 24/7 and the devs need to maintain servers so that your code gets executed.
i'd suggest just getting the simple game and run the server locally. no longer MMO in that case, but thats probably for the best until your code can handle raids by other players :)
https://screeps.com/