This is really cool idea. But don't you think taking material and saving specific sentences may add unnecessary mental pressure to the process of learning which is said is ideal when the student is in a playful mood?
True, I would say though from my personal experience there is a serious study element inherent to learning languages to a high level too. So it depends on what the user wants, there are gamified apps like Duolingo but the efficacy of it has been questioned over the years