hello, I quite like duolingo but I have two really annoying grips with it :

• It repeats too much some words (that I remember) and not enough others (that I don't remember).
• There is not enough source to target translation.

I noticed that several people I've discussed duolingo with where also complaining of it.

Because everything is already here, my guess is that the algorithms just need to be adjusted, and nothing to be developed. So it could be resolved easily.