Q-den / Calculator like puzzle

Q-den is a puzzle game that looks like a calculator.
You can calculate on the calculator to press just "?" buttons. Then, you will guess what kind of buttons those are from the results of that calculation.
First of all, you do the calculation to press "a number button","operation button","a number button" and "= button" in order to.
The result will be displayed, and then guess what kind of calculation you did.
When you know an answer, press and hold the button,
the dialog will be displayed, then you can select your answer and set it on the button.
When you press "correct" button, the correct roles of the buttons will appear.
On the panel, the score and the number of correct will also appear.
In addition, the "correct" button is a toggle, "answer" button redisplays your answer.
You can set game mode :
Select android menu key / Level Setting to open setting page. You can choose one mode from Easey1, Easey2, Moderate, Cool, and Hot.
In Cool and Hot mode, a part of the calculation result is hidden. It is difficult to guess what kind of calculation it is.
The bottom panel of the screen shows descriptions of each mode and how to play. (but the documents are only in Japanese.)