On commodore 64 the screen is just a fixed size grid of characters. No one ever had issues making an ui. We pretend but flexible viewport size is not actually possible. If you are making a painting for example the size of the canvas greatly influences what can and can be done.

I made a stunning landscape photo one time that looked great only when displayed at roughly the size of a hand. If made larger undesirable details became visible (littering), when smaller important details were lost (a formation of birds over a fishing vessel).

> We pretend but flexible viewport size is not actually possible.

Not beyond a point, but it's still very useful to be flexible up to that. For example, I'm very grateful that a web page will reflow text rather than print everything on one line and force horizontal scrolling.

Yet, for some reason, mobile browsers do not reflow when you zoom in, but instead insist on horizontal scrolling, unlike their desktop counterparts. I've never understood that.

Firefox has a "Desktop site" switch that when disabled changes this behavior.

No, it does not change the zoom behavior.

It is not like we have a choice. I forgot to mention that people also have different eye sight which further complicates things. Some set the font so large half the apps fail to fit. Before many people had one I see someone browse using an enormous TV with very high resolution. The google adds sidebar lived on the other side of the room. % size images upscaled into a pizza of artifacts. There wasn't a website that looked the way intended. A funny I ran into once was Lubuntu system dialogs with the accept button below the screen. I've also seen enough print previews where one cant read the text. The use of colors with poor contrast only on some displays.

We are having a lot of fun pretending it is possible.