Lesson and Practice views with a progress column

A chapter opens on two tabs. Lesson holds the explanation and the exercise; Practice lists the chapter’s judge problems.

At 1200 pixels and wider, a column on the right lists the lesson’s sections and how many core problems you have solved, with extra problems on their own row. Narrower screens get an On this page list under the tabs.

The chapter sidebar sits against the edge of the window and groups chapters the way the map does. Its search ranks chapter names first and opens the best match when you press Enter.