A suggestion about teaching grammar on Duolingo
Before I start, I must say that this website is fantastic! Learning a language hasn't been so easy. But I was thinking, this website focuses a lot on vocabulary, and I think it would be a great step forward for it to expand on teaching grammar. For example, in french, adjectives come after the noun, (expect if the adjective is about beauty, age, numbers, goodness or size) but unfortunately it's difficult to come across that sort of thing on this site.
So I propose that the site covers this. For example it asks questions like " Where does this adjective go before, or after that noun?".
I think that having a tip that explains the grammar is way better that asking grammar questions. Simply is not a natural way to learn a foreign language. English isn't my first language, and most of what i have learned, came from reading text, listening people and songs.
I rarely analyse a sentence gramatically, much more often i question, does it sound good? or it sound weird? and for me, it works most of the time because, i tried to listen as much i can, rather than analyse the grammar Of course, sorry for my english. ; )
By the way, fantastic site!
Something else that might be helpful, a new style of question: "Correct the error." I know it would be a very helpful method for me to practice the nominative and accusative cases and distinguishing when to use der/den/dem or ein/eine/einem in German if they'd say "This phrase is wrong, type the corrected version below." Or, to help with spot identification of poor construction, you could ask "Does this sentence look right, [yes] or [no]" so students get an instinctive feel for what a correct sentence look like.
Or perhaps Duo can offer advice as you move through the lessons. When you first come upon an instance of this, he can offer a tip to help you with these types of scenarios. In subsequent instances, he can be there with a reminder tip that you can get by clicking on him or something.