Tonify
Mandarin pronunciation, graded.
Problem
Mandarin tones are the part of the language least served by reading practice. A learner can know a word’s meaning and characters and still be unintelligible, because the tone carries as much information as the consonants, and self-study gives no signal about which ones are wrong.
How it was solved
Drill the tones directly rather than the vocabulary around them. A word is presented, the learner produces it, and the result is graded, so practice returns a verdict instead of a feeling.
Results
Running at tonedrill.com, with feedback collected in the app itself.