The big idea in Leitner’s system is that some facts are easy to learn but hard to remember while others are the opposite, and that adaptive repetition reinforces long-term memory. Further, he realized that concentrating one’s study only on the things that are hard to recall is discouraging, for lack of positive reinforcement, and so it helps to mix things up. Can’t remember this fact? — bring it back tomorrow for another try. Got this one cold? — great, but you probably won’t need to repeat it for a while.
Herr Leitner’s system came a bit early for the personal-computer age, but computers have certainly widened its appeal, and there are now many generalized cardbox-study tools to choose from. One thing that fits exceptionally well on a flashcard is a word-anagramming question like '''<tt>AEINRST'''</tt>, with the answers on the back, and the impact of this study method has transformed how word games are played.
== Cardboxing in Zyzzyva ==
One feature of Zyzzyva that favored the dedicated game player was its implementation of the Leitner Cardbox System, by which the user could build up a hoard of anagram questions for long-term study by doing anagram or pattern searches and then committing them to the cardbox. Users’ pain tolerance varied, but it became common for Zyzzyva users to amass a cardbox stuffed with many thousands of virtual flashcards, usually the ones deemed most probable to appear in gameplay, and particularly the ones of seven or eight letters that could earn the prized 50-point “bingo” bonus that often decides a game.
One of the genius things about cardboxing in Zyzzyva is that you get to decide what’s a “passing grade” for remembering the answers to an anagram question. If you’re happy enough that you remembered eight of the nine answers to '''<tt>AEINRST'''</tt>, mark it correct and move on. If you’re a bit obsessive and can’t live with not remembering '''<tt>ANESTRI''' </tt> (again?!), mark it incorrect and know that you’ll get it when it comes back tomorrow.
In Zyzzyva, the word “cardbox” has two meanings: Your virtual cardbox contains 16 compartments, numbered 0 to 15. Words you add to the (aggregate) cardbox normally start out in (individual) Cardbox 0 and step up from there as you answer them correctly; an incorrect answer demotes a question back to Cardbox 0. Of course, you can pluck questions out and move them around as necessary.