When you touch a spiral copied the shape from Ammonite, You can get a sound.
The pitch of this sound will be obeyed where you touch. More closer to center, Higher Pitch. And One round means one octave, a white line from top to center means Pitch of "C".
You can see guidelines on a spiral to play music.
Two type of guidelines are prepared. One is a scale of Just Intonation of C-major, The other is a scale of Equal Temperament. You can switch whether guideline can be seen or not.
That's all. Very simple App. Please enjoy playing a new-type Interface instrument!