💻 Redesign coding and adventure screen

[t1u1]

When there are many exercises in a page, they occupy screen real estate and also intimidate the students.

Suggestion:

By default, a page could just show the first exercise or introduction text, and collapse all other rows.

The student can expand or collapse the other rows by their choice. The system can remember their choice, so that if they navigate away and come back to a tab, they will be back in the same context.