Earlier quoted context omitted.
This is hard and often done wrong- mobile phones are usually high dpi and have gotten quite large, so it can be hard to distinguish between a large phone and half a desktop screen. Some people get quite annoyed by being bumped into a mobile experience when you resize your window from fullscreen on a laptop.
> This is hard and often done wrong- mobile phones are usually high dpi and have gotten quite large, so it can be hard to distinguish between a large phone and half a desktop screen. A tablet could be easily confused, or a phone in landscape mode, too, but for a phone in portrait mode this seems a bit hard to imagine, because DPI is taken into account when converting the display width into CSS pixels, so even a phone…
Also, many times mobile breakpoints don't look at the device orientation and pick numbers like 800px, to capture landscape orientation on medium sized phones or something (I'm not sure where this number comes from to be honest). This obviously breaks the two windows side by side case on laptops but is a top result for me if you google the arcane syntax for how to target mobile browsers with a media query.
I am not 100% sure what all the pitfalls are with the current interface, but they exist often enough for me to run into them semi-frequently on smaller laptops.