What's the point?
To me, this app is most illogical. Perhaps it's supposed to help one "spot" situations in which one might take advantage, but, it flies in the face of how one normally tries to do a chess puzzle, that is, to determine what's the best next move. In this app, I'm supposed to "play" BOTH sides, which are supposed to "cooperate" to defeat the Black king; not only that, but to cooperate in my own defeat when moving for Black, I may have to make a "legal" but incredibly stupid move in order to allow White to win. Does that make any sense to you? It doesn't to me.