I am still evaluating Drops, but very concerned about the use of romanized versions of phrases and words for languages with non-English alphabets or scripts. This is heavily discouraged by most language teachers, as it both delays the absolutely-necessary acquisition of the language’s written form and usually teaches quite incorrect pronunciation. This is certainly true of Korean, the language I am learning.
Can you add a way to control this in Drops, so that, for example, it ONLY uses Hangul for Korean training, including all the spelling drills?
Another suggestion: provide an alternative ordering of vocab blocks based on frequency of use. Again, this is commonly-recommended by language trainers - to acquire vocab not by topic or subject area, but to mix topics across an ordering that gets the learner up and going on the most-important words to learn first.