This app lets you to understand the difference in pitch between Equal Temperament and Just Intonation.
This is a limited version of "Meantone" which is an app you can listen and feel well tempered.
("Meantone" also has not only Equal Temperament and Just Intonation, but also 2 types of Pythagorean, 4 types of Meantone.
If you want to confirm other temperaments, I recommend that you purchase an app "Meantone".)

On Just Intonation, Twelve degree's pitch aren't fixed. Each degree's pitch depends on a key. And an enharmonic pitch is different. For example, C# and Db are different pitch.

How to use is as follows:

-How to operate music
flicking a music view left or right, changing a key.
flicking a music view up or down, changing a clef.

-How to play
Tap a music view where you want.

-Switch of Equal Temperament and Just Intonation
Using the switch in center of view, you can select "Equal Temperament" and "Just Intonation".You can switch also during sounding.

-Switch of Polyphonic and Monophonic
Turn on "Poly" switch, then you can input a new note when you tap a music. If you tap same position once again, the sound will stop. So you can get a chord sound by tapping several places. And if you want to stop all sound, tap "All Off" switch next to Poly switch.
Turn off "Poly" switch, it sounds where you are touching. If you release your finger from a music, the sound will stop.

-About pitch display
In a Hz display, the real frequency is displayed. In a cent display, it displays a cent value against a keynote of current key, or a cent value against pitch A. You can select a standard of cent.