The Challenges and Actions document describes your gameplay by listing (and organizing into a hierarchy) the challenges in your game and the actions that the player takes to meet them. It forms part of the Game Script that gives all the details about your game.
Consider using the following process for designing your challenges and actions (but see below for the form of the Challenges and Actions document).
Organize your Challenges and Actions document as follows, but note that you write the document per the process above. (e.g. let the design questions guide what subdocument you work on at what points in the design):
A one-page description of your most important challenges and actions.
Refering directly to the list of challenge types on pages 23-24 of your textbook (Fundamentals of Game Design, by Ernest Adams and Andrew Rollings — the challenge types are further described on pages 289-302 of your textbook), make a table that lists which challenge types you will include. Do this as you answer the Design Questions for your Gameplay — Challenges and Actions. As you continue answering those design questions, expand the table to provide the specific challenges in your game for each challenge-type that you include and the actions that the player can do to meet the challenges.
As you answer the Design Questions for your Gameplay — Challenges and Actions, develop a Hierarchy of Challenges like that pictured below (adapted from pages 254 and 257 of your textbook, Fundamentals of Game Design, by Ernest Adams and Andrew Rollings).
Answers to the Design Questions for your Gameplay — Challenges and Actions.