Constantly changing the app to be more inclined towards making money even though they already run soooo many ads. A few years ago you did not need hearts to do unlimited lessons, but now they force you to use hearts in order to buy more when you run out. Can't wager for gems anymore, etc. It's all about the money, and not so much about the education. They don't even consider more affordable subscriptions for weaker currencies in poorer countries.