Boustrophedon writing systems are ones in which the direction of writing swaps after each line.
At least one conlang is intended to be written as a boustrophedon (in that case vertically.)
Now if you manually typeset a document your could reverse the lines, but that doesn't allow for plain text boustrophedon writing, nor does it allow for reflowable text (such as on a webpage.)
Are there any ways of encoding text in Unicode to mark it as boustrophedon? There are multiple text direction control codes in Unicode, can any of them be used for boustrophedon text? Or has anyone proposed a control code to be included in Unicode, or designated one in a Private Use Area?
Or are there any other practical ways of publishing boustrophedon text (because a custom PUA code wouldn't be supported by most software) such as some kind of CSS filter for a webpage?