At my home in Kolomna, I have a book called “Chemical Trainer” from 1986. I have never seen anything like it before or since.
The material of each of the 54 programs is divided into many small, very short sections, or categories. At the end of each category, one or more questions are posed. This is done to check whether the content of the category is truly understood. For each answer, there is a place in the book to jump to in order to see if the answer is correct. If the answer is wrong, it describes why and asks a new question. If correct — you move further in this quest.
These Germans in 1986 created an interactive textbook even before it became fashionable.
Hi, I'm Rauf Aliev. 