It would be nice to have screenshots. Also it’s just a single commit, did you use AI? Quoting the readme: “FPS.cob is what you get when you decide that game development is too easy nowadays”.
As a few people have asked for screenshots, I spun it up. Here's a video of the basic gameplay: https://peterc.org/misc/fpscob.mp4 .. it's clunky, but it does play.
I had to get into an old tcl program for work recently and had the same thought. I wouldn't necessarily pick it today but it was kind of nice in a way that's unfamiliar to me from modern development.
https://github.com/icitry/FPS.cob/blob/main/fps.cob