It's weird, because it's not very good at understanding the need of the users. If you are Chinese and want to learn English, you have to show the contrast between the grammar-points from a Chinese perspective in an meaningful way.

It really feels like: how can I, as an english developer, teach language? Instead of: -How can I, as an elite teacher, create an app to teach language?

Now that I think about it... is there any teachers with SF-developer-salary? Is there any language-teachers that talk about being the 10x teacher?

Duolingo has done some cool stuff with AI: http://sharedtask.duolingo.com/ they just don't seem to use it?