Ask HN: ChessMobi – My first iOS chess training application. Feedback welcome

I am launching today my side project for ios: ChessMobi. It's a chess application targetted at club chess players willing to improve.

The URL on AppStore is: https://itunes.apple.com/app/id892425054 The landing page is here: http://www.chessmobi.com/

The material ( 3 volumes for the moment ) is curated by two professional chess trainers. Additional volumes are in the working and I am in touch with an old famous GM ( albeit retired from professional chess ) for additional content. I would like to receive constructive feedback from the forum regarding what can be improved and how to promote the application and reach additional audience. Also, after all the work done, sharing with me what you like wouldn't do any harm :P.

Thanks in advance!