Pretty good app up until payment wall. I don't mind paying because the lessons are well designed and the app is great. I do mind that there's no monthly payment option. Also, they only proposed 2 payment options : PayPal or input your credit card numbers. No google payment - which means if you have an issue or want to cancel, you're guaranteed it will be near impossible. Also, no idea how robust their app is security wise - so don't give your credit card details obv. Shame...