Plans to add more in depth grammar explanations?
For example, just starting out in German and I will be marked wrong for a word being masculine or feminine, or neuter. But there is no where to go to find explanations on what makes words a specific gender.
Any plans to add a grammar source to read through? Otherwise everything is basically trail and error the first time around.
At each lesson there is a link "View all vocabulary ...". Basically you just have to learn the genders with the words. There are very few rules that only apply to some words. I.e. words ending in "-chen" or "-lein" are always neutre ("das Mädchen" - "the girl"). Words ending in "-e" are mostly feminine. Exceptions are "der Käse", "der Junge", some Professions ("der Geologe") and few more. Duolingo does not substitute a good grammar book or a dictionary. You will need these all along, if you seriously want to learn the language.
I totally agree with kragi. I would recommend that you find a good introductory text book or two and read through them in addition to the lessons. The duolingo lessons aren't bad (in my opinion), but, like you pointed out, they are extremely weak on grammar. I guess you are supposed to pick it up by example, but it has certainly been helpful to me to have an actual grammar text that spells it all out in black in white. Two that I have used (and still use) are called "Deutsch Heute" and "Wie Geht's" respectively. They are introductory college level texts (but perfectly suited to a complete beginner).
A brand new, current edition will be very expensive, but quite often used older editions can be bought on Amazon for next to nothing. In fact, I see there are several copies of Deutsch Heute Seventh Edition (1999) available right now for $4.00, and that includes shipping. Just make sure you get an edition that came out after 1996. In 1996 there was an official German spelling reform, and many words were changed. You want to make sure you get a book that uses the new spellings, or you'll just be confused (the 7th edition of Deutsch Heute does use the new spellings).
@Wanhope: I think you shouldn't have any trouble finding a used, older edition of Deutsch Heute (or other) text. When I cheked the other day, a brand new current edition ran around 140 dollars on Amazon, but a used earlier edition (specifically edition 7 - several copies were available) could be had for 4 bucks delivered. And I wouldn't worry too much about having an old edition, and here's why I say that. When I originally studied German in college, we used Deutsch Heute edition 2. I actually still have that book, even though I suppose it's getting close to 30 years old. But I actually use my copy of edition 7 because it uses the post-spelling-reform spellings. There are ~17 years separating edition 2 and edition 7, but very little of consequence has actually changed. Yeah, there's more color pictures and so on in the new book, but, so far as actually teaching the grammar of the language goes, the book is still pretty much the same as it was in its second edition (only now with the updated spellings). Get an old book. The language hasn't changed. Everything still applies. The old editions are just WAY cheaper.