The app works in combination with the book, and only through that, the experience is complete. As it is not a typical app, that can be used as a distraction from life, but rather to teach something, I rather wanted to structure it differently, than most known apps and give it a booklike feeling.
Furthermore, with the app, I wanted to support the different learning types of students. While some students learn best through reading texts, others can memorize things better through listening or visualisation. As it is not possible to combine all of these in a textbook, I did this within the app and give students the option to choose what they want to use.