Analyzing stuff (especially code) down to the last detail on that layer of abstraction. I can tell you one fact about how bad MCreator generated code is, and a lot more about random code bugs (often minecraft related).
The local train line i use nearly daily during the semester.
A bit less reading manga and watching anime.
I also play a bit of osu.
But generally nearly everything that is some kind of intrinsic relation (not names or model numbers but how something works etc.) is interesting for me.
Do you know shattered pixel dungeon? Its an open source rougelike that you can play on your smartphone or pc.