mxklabs' privacy policy for the app 'The Appies: Graph Puzzles':

To be able to recall how many levels a user has successfully completed the app does store a list of completed levels in the internal (e.g. private) storage area of the app on your device. This is the only information the app stores.
The app does not and will not at any point in the future collect any information about its users.
The app does not and will not at any point in the future have any ads.
The app does not and will not at any point in the future have any in-app purchases.
The app does not and will not at any point in the future send any information (about users or otherwise) to any servers.