Unconventional ideas for a brain training program or a series of books
1. Kim's Game
The classic memory training game from Rudyard Kipling and Scouting
2. Unintentional learning.
I discovered this when I was a child. My Dad and a couple of his classmates were studying and quizzing each other for one of their law classes. I was in the room but busy doing something completely unrelated. Not even sure I understood all the terminology or concepts thy were discussing. But I was able to regurgitate a surprising amount of the information. The same idea could be intentionally applied to learners.
You could have a book of outlined shapes and the user would have to use the provided pieces to solve the puzzle.
4. DIY Tangrams
Here are your pieces. How many different shapes or patterns can you create.
5. Language learning.
No idea if this has been tried or if it would work:
Design a course where the students are listening to a piece in the language they are training, while at the same time, they read along in their native language.