Ask HN: What rabbit hole(s) did you dive into recently?

You get nerd-sniped. Assigned a bug to squash. Some new tech or gadget arrived, to familiarize yourself with.

While researching / reading up / debugging, you stumble upon something interesting. Upon looking into that, yet another subject catches your attention.

You know how this goes. So... (see title). Bonus questions: what intermediate steps did you pass along the way? What stuck in your mind the most?