> There are way worse things for your mental health than habitual physical activity. I'd bet half the people here would benefit from a good tunnel project.

In the update[1] he says it's calming and makes him feel safe. He's happier after doing it.

It doesn't sound so bad. I mean, it's gotta be healthier than so called idle games, and about as useful. Or similar to lifting weights or jogging or something. It makes him feel good, that's all the justification any non-harmful activity should need.

[1] Mods removed it on Reddit. Archive.org: http://web.archive.org/web/20220417170609/https://old.reddit...