One good way to learn code is also via flash cards. The concept of spaced repetition, which basically weights easy questions lower is already implemented in the free and cross platform (even working on mobile) tool Anki.
There is also an r package called r2anki, which allows to import the r code highlighting into the flash cards. The pkg is still in dev, but already works. Here the talk from @henningsway at use!R.
The challenge would be to create tidyverse learn cards. I'ld guess starting with translating tasks from a cookbook or examples from cheatsheets would be a good start to create tidyverse flashcards decks.
The cool thing is that these decks can be synched and shared via anki online, so that the whole community would profit from anyone who creates a deck. Also for package authors this would be a nice thing to promote their pkg. And it could also be used to switch from dplyr to data.table, etc.
Of course there are many other approaches as mentione above, but the anki approach would be really easy, it could scale and even beginners could design flash cards.