Thank you! For both the explanation and the vocabulary (search terms). "Viewport" is one concept I was missing, and I was dancing around "scale" with things like "variable size".

I hope that a 10" tablet with a width of 2k pixels is similar to the phone case, but it sounds like I should find some way to confirm that before investing in one. That form factor is pretty common now so it's *probably* ok, but most people's vision is better than mine so I want to investigate.