For example, your chapter structure could look like this:

A course is a collection of chapters, similar to a paper textbook. It's used as a clearly defined course, with a learning path.

All content is positioned, presented, and organized within chapters. A chapter is a collection of subchapters.

Subchapters are a collection of theory and exercise packages. Subchapters are always positioned within a chapter.

Theory can be one of two forms:

Theory is always positioned in a subchapter, which is positioned in a chapter. This means that a theory page can only have one position; it can't be positioned in multiple chapters.

A package is a collection of exercises, and can therefore contain:

Theory and package are on the same hierarchical level, and both of them are positioned in a subchapter, which is positioned in a chapter. Usually, in a subchapter, the theory appears displayed first, followed by an exercise package. This is just a convention we have adopted when presenting the content but well could have been the other way around where an exercise package appears first and the theory comes second.

Individual exercises are not connected to a package, subchapter, or chapter. This means that they can be positioned in multiple packages, and thus in multiple subchapters and chapters.