The problems in this set are "labs" where you can experiment with a new means of entering the text of a PG problem. There are examples, and reference materials in the menus within the problem.
The first problem experiments with PGML, a new proposal for a PG Markup Language.
The second problem experiments with a new context that lets you typeset most mathematical expressions that you need for PG problems.
If you want to write your own problems using PGML, the macro file and examples are linked here: