Module catalog 

The catalog: every section and level, in course order.

Structs

Catalog

All sections and levels. Iteration, Catalog::next and Catalog::prev follow the course order, which is numeric on (section, number), whatever order the sections and levels were declared in.

UnknownLevelError

A level id that is not in the catalog. A stale saved id must never be mistaken for “the player finished”, so asking for the neighbours of one is an error, not None.