An excellent introduction from Jen Simmons on writing modes on the web. Did you know that among all the current browsers it’s only Opera Mini that doesn’t support writing modes?
Using writing modes provides you much more scope for change when it comes to different language support (not to mention some fresh design layouts), and it also helps link some of the syntax that seems strange across Flexbox and Grid.
Whether you know about it or not, the writing mode is the first building block of every layout we create. You can do what we’ve been doing for 25 years – and leave your page set to the default left-to-right direction, horizontal top-to-bottom writing mode. Or you can enter a world of new possibilities where content flows in other directions.An excerpt from CSS Writing Modes