. >> and it's also something >> estimate that as an -pplication that i haven't had here.applications and the best ones that we see on the market today, we have in them adjusting in real-time. and maybe that is advancing at a student can go a little bit further and this gives a good review from us because it has lots of things that we like to see. adapting levels of difficulty. john: there's another one called mind snacks? >> guesstimatehat they do is they have language learning apps and then they have a vocabulary application for kids. this includes a number of different vocabulary games and has the adaptin levels of difficulty and remediation and the best ones that we see are those that are most sensitive to what the learner can do. john: we ve reviewed almost 3000 applications, only 10% get a grade a or grade b two. >> that's right, we review what has been told is most effective from the usability design perspective. the sad fact of the matter is that there are just not a lot of really high-quality instruction on the mrket. john: but there will be because they have to c