As a licensed amateur radio operator who is currently learning code, I can confidently say that this is an awful way to learn Morse code. This tree method is a nice novelty but try thinking dits and dahs at 25 words per minute and higher. You'll be lost in a matter of seconds.
The true method of learning Morse code requires "habit forming". Where you write letters bases on the rhythm of the characters, not by thinking about dots and dashes.
If you'd like to learn the code google the "Koch" method. Some great free programs include "G4FON Koch Trainer", "Morse Machine", "CW Player" and "Morse Runner".