It was my favourite app of all times, the one that I did spent at least 2000 hours on it. Couple years later, this app is not even useable anymore. You lose half your time watching videos. If you want to remove the ads, you have to pay 18$/month if you don't want to pay 120$/year in one payment. Use to be the best app in the store for learning. Now I'm so turn off that I delete the app right away. So sad to see that everything that has succeed ends up in a hustle.