Rumble Stars is free to play, however they also offer optional “in-app purchases”. While such purchases are not required to play the game, they can be used to progress at a faster pace. 

In-app purchases are paid for with real money, and are always clearly labeled as such. They’re accessible “in game”, meaning that the options to make a purchase are found within the game itself.

Important: You can easily manage the ability to make in-app purchases, adjust password protection settings, or disable in-app purchases entirely through your mobile device’s general settings. The instructions you need can be found here: