Unfortunately there's an issue with the ads. I click to get gems, it screws up completely and won't let me back to the game, resetting the 200-300 wave I've got going. Also if I ever accidentally exit the app while I'm working or doing other things on my phone, it resets my waves. Very disappointing especially since this game is so fun and addicting. Will give it more stars when problems get fixed🤷‍♀️