Mettle is a walking RPG: party up with friends and let your real-world steps slay monsters.
Questions, bug reports, feedback, or data-deletion requests — email danielchungfung@gmail.com and I'll get back to you as soon as I can. There is a Send feedback form inside the app too, under Settings, which reaches the same inbox and tells me which version you are on.
There is also a Discord, where the other players are — often the faster answer for a question about how the game works, as against something that is wrong with it.