[vaporstun]

"Regarding point x, it's not that screen size is calculated on the diagonal; doubling the diagonal (and keeping the same aspect ratio) doubles the width and height as well."

I assume you meant point y. Anyway, right you are! This is what I tried to express by saying "By the rules of Pythagoras" because I was lazy and didn't want to take the time to calculate it precisely. I also assumed most people here would understand the implications, but on reading your comment I realized they may not and what I visualize in my head is likely far different from what everyone else does. Thank you for making it much more clear and explicit for me!