I was thinking it'd be pretty convenient if there was a feature to print flashcards. Maybe for each lesson there could be a button to print all the words you learned, and perhaps a line where you could add your own notes. There could be a default size and amount printed per page (maybe 4x10), with lines separating each box where you could use a scissors to cut them individually.
Just my thoughts. I imagine it'd be a relatively easy feature to add, and it'd only attract more people to your website.
I had a similar idea only in app using word count.
Click On "word count" User prompt to choose language (e.g. If it was Italian or English) App pops single word with space for user to write translation
Simply cycling randomly through the list of known words