FYI: The difficulty ratings are automatically assigned to the quotes based on length. The 'difficult' ones are the shortest and the 'easy' ones are the longest. That is why some of the ones labeled 'easy' or 'average' can be quite challenging, and some of the 'difficult' ones can be quite simple. In general, though, the difficulty ratings do correlate with the actual difficulty, especially the 'easy' puzzles. So you could definitely print off some of the 'average' puzzles as well, as you'll probably have to do a lot of refreshing to only get 'difficult' puzzles.
"For where your treasure is, there your heart will be also."