A small listening game: each character sings out a line, and you decide whether it really was their voice or an impostor.
The game is played by ear, so sound has to be on. Check that your device isn't on silent and the volume is up, then open Settings inside the game and make sure Sound is switched on.
Each level has 10 rounds and pays out up to 3 stars. Stars add up across levels, and once you have enough the next character opens. If you're stuck, replay an earlier level to pick up the stars you missed.
Only on your device. Nothing is uploaded and there's no account. Deleting the app removes your progress, and Settings → Reset Progress lets you start over on purpose.
Something else not working, or an idea for a new character? Write to verena@prazilo.info and tell us your device model and iOS version.