A lot of variables aren't really considered for the first prototype of the learning and reviewing system.
One of them (and very important) is time and the generation of reviewing frequency.
Until the first prototype and the arrival of the RTC there is no option for the tracking of time on the raspberry pi.
Also, there is a difference between the actual learning system of the alphabet. I was dealing with the amount of letters to learn per session, and the exercises were a randomly distribution of those letters. After coding the word learning algorithm, I realize that a big exception (when you were in letter 24 you only have 2 letters left instead of 6 for the rest of the code) could be skip.
So, the person learn one letter, and the other five (to complete the six buttons) are randomly selected from a the alphabet (which doesn't include the letter that the person is learning)
Also, there is still some general problems with the conception of the reviewing code. One of them, is that I'm actually not tracking the number of right/wrong answers. Should it be in the same json file or another?