I can understand that. I've always coded for fun (Basic, Turbo C, lots of psuedo languages, then perl, sql, php, python and so on) - learning that stuff is hard for me but very rewarding when I do. I actually find it harder to learn stuff at work, but it's great to do at work too. I transfer skills between the two schools - and each has enough variation that whilst there's technical and skill crossover, the headspace is very different - at least for me. But yes, if I've been doing that all day, I'll do something else in the evening. I restored a car as a distraction from work once, but that was when I was in a job that I really hated.

High five for factorio mention. Incredible game, although I'm playing more Captain of Industry lately. Different but similar brain scratching.