Feature request - Cloze only unmastered words

I like the feature where you can create private cloze collections, for instance by importing books. However, the automatic cloze generator often generates clozes of easy words that I already know and have mastered. It is a bit of a pain in the ass to manually set all of these sentences to mastered.

It would be great to have an option to only generate clozes of unmastered words. So you can for instance input an book or article and automatically a collection gets created with sentences with unmastered words, where the unmastered word is clozed!

Interesting idea, I like it! It could also be interesting to have ability to randomly reassign Cloze words in entire user collection, just to freshen things up.

Btw I find it’s very easy to change cloze word in iPad and iPhone app (not sure if you’re doing it on browser, but for me with Safari it’s not as easy as with the app)—I do it on the fly as I play the collection, it keeps me actively involved and gives me yet another opportunity to read through the entire sentence.