Examine the classic theme files in the Sphinx repository, specifically the 'sphinx/themes/classic' directory. Look for the 'static/classic.css' and 'layout.html' files. Add CSS media queries to make the theme responsive for mobile devices. Ensure that documentation content is readable on small screens. The existing comments suggest no prior work, so start fresh.
Mobile browser support of the classic theme · sphinx-doc/sphinx#2611 | Good First Issue