This app was mentioned in 2 comments, with an average of 1.00 upvote
Hey, I would personally focus more on:
I would do this because I think Duolinguo does often not have very natural sentences and could give you bad habits, which natural Korean won't give you. I don't know what your end goal is, but I think this would be a good approach. The Evita sentence deck contains grammar and if you don't understand something look it up, I think you will be more likely to remember than if just randomly learning grammar.
For super beginners, from zero ... this app taught me how to read: PopPopping Korean.
Not an app, but there's also the famous "learn to read Korean in 15 minutes" graphic.
I've looked around quite a bit over the past two years, and the quality of the Korean language-learning apps are really low, compared to the apps for Japanese or Mandarin Chinese. I'd say it's about 3 years before the scene catches up.
Personally, only PopPopping Korean, Memrise, and Google Translate have been of any use to me.