On the technical front, CSS is extremely well-placed for this, with the comparatively recent shift from absolute axes (margin-left, border-bottom, &c.) to directional axes (margin-inline-start, border-block-end, &c.), with what those axes mean depending on writing-mode, direction and text-orientation.
Browser support for the complete set of this stuff is still a tad patchy; Firefox is best in general, but all the browsers have at least the basics.
But yeah, it mostly seems to boil down to rotating your app’s entire layout by 90°.
> On the technical front, CSS is extremely well-placed for this, with the comparatively recent shift from absolute axes (margin-left, border-bottom, &c.) to directional axes (margin-inline-start, border-block-end, &c.), with what those axes mean depending on writing-mode, direction and text-orientation.
Yeah... even if CSS itself is, the browsers are not at all, not even close. Recently I tried to use a vertical `writing-mode` in a relatively simple application and encountered a massive amount of layout bugs and issues; it's pretty much totally broken in both Chrome and Firefox (unless maybe if you set everything to a vertical writing mode then it might kinda work?), and no one seems to care.
The attribute used on the Mongolian president's site linked above is "writing-mode: vertical-lr;". It seems like Electron & co. may be the best options for apps.
Browser support for the complete set of this stuff is still a tad patchy; Firefox is best in general, but all the browsers have at least the basics.
But yeah, it mostly seems to boil down to rotating your app’s entire layout by 90°.