Literally, the only feature I'm missing on Doulingo app, is the lessons text.
I really don't understand why we can't have those on mobile, On work days (majority of days almost all of us) I study on mobile on the way to work, and allot of times I get to a point that I'm just guessing the solution over and over because I don't have the lesson materials to understand the grammar rules.
I'm with you, this would be fantastic. I love Duolingo but my main gripe would be the sheer lack of explanation with some things. Having the study notes is at least part way towards that.
.. study on mobile on the way to work ..
.. lesson materials to understand the grammar rules.
Open www.duolingo.com in the browser of your phone, and set your browser in "Desktop mode"
In the browsers Firefox and Chrome you can select the "Desktop mode" via the three dots in the upper right corner of the browser.
(It seems to be not possible on iPhones with a small screen)