I find this app quite fun to use and I have already finished a view levels. Im struggling a bit with recall and retention outside the scope of the game, but that may just be me.
My main complaint about this app is that (according to my Chinese friends) it teaches a lot of very formal words that are rarely used in daily conversation, rather than the more commonly used ones (e.g. handsome = ying jun vs . shuai)
Second, it teaches words you really dont need to know as a beginner (e.g. "submarine" in the "Transportation" category - really!? How often are you going to take a submarine somewhere?).
Learning a new language is already hard enough. No need to fill up our memory space with useless vocabulary.
Finally, the algorithms that reenforce words you dont remember well is extremely weak. If this app were to use "Spaced Repetition" or "Leitner" it would be significantly more useful. Calling a word "mastered" just because you got it 10 times right isnt very realistic.
With these issues addressed, I would give the app 5 stars. Without it, its just a fun game but without much real teaching power.
MegaThrust about Learn Chinese (Mandarin) by MindSnacks