I'm working in Linux internals and, for a bit of recreation, electrical engineering. Plus 3D part modelling. With some machining. And a wander through retro computer, retro console, and clone builds. Maybe a bit of applied materials and material sciences.

And when it comes of well (or horribly) I'll edit down a video of it so everyone can learn from it (or just have a chuckle)!

The 3D printers have been invaluable in creating tools on the fly and replacement parts. When I've got something cooked up I make a video of the process and release the files under a license that encourages re-use (although to be fair, copyright doesn't apply to technical designs or descriptions... those require patents).