One way the user can make sure they’ve understood the material is to do exercises. They should usually be on their own lens, as additional “homework problems” that users can solve to get more practice. They can also be embedded in the explanation pages, so the user can solve them as they are learning, especially on path pages where the reader has asked for exercises.
Many pages could be improved by adding exercises, but priority should be given to:
Pages which don’t currently have exercises.
Pages which have a full explanation of a concept (rather than just defienitions).
Pages which are a requisite that many other concepts rely on.
Pages which are mostly self-contained, rather than overviews of a large and multifaceted concept (exercises should go with child pages explaining the subtopics).