A great wa to practice
This is a great way to practice and its accessible to the blind! Its reminding me a little of Duolingo. However, I dont think someone could go from first-time vocalist to singing champion using only this app. I know your goal is to be a "singing coach in your pocket". For that, I think you need more categories of improvement, and I would instruct people more on breathing technique and good vowel and consonant form. Also I think vocalists generally should know how to read music. Maybe make a separate app called Vanido Technique for form, breathing, and music.
Keel haul about
Vanido - Your personal singing coach, v0.3.2