These changes make a number of improvements, mostly typographical, to improve readability and to render properly on small devices.

Universal increase in font size
Use same font as ss.org for consistency
Remove unnecessary visual noise (borders, box shadows, etc)
Use Google PrettyPrint syntax highlighter for improved readability of code sections
Fully responsive, with hamburger menu
Add "section" linking mode to menu items
Add masthead for breadcrumbs, introduction
Improved styles for notice/info/warning messaging