Legos; also the ender 3d printer. I had a nostalgic time putting the ender together. Felt like a lego set. That's not saying it was trivial (it challenged me) but that I trusted it every step of the way not because of previous experience, but because of the obvious well-designed aspects of the experience as I was putting it together. For example: I put on a part sloppily, and trying to attach anther part was the first real resistance I felt in the entire process -- physical that is, I had to study every page of the manual for a minute or two before even being able to figure out what the next step would need to be, but it was always clear after studying.