Your brain is far more advanced then any app you can download. Plus, its waterproof, rugged, and thick (atleast mine is
). There are 6-10 basic knots you should know. Just sit down one night with your laptop and learn them one by one. Then whenever you are watching tv or watching a movie after that, make a point to practice tying them. No reference needed thereafter.
This works, I know, because I did it two weeks ago.