Dentaku the Calculator

In 1981, the German music group Kraftwerk released a song played on a calculator. The title of the song is “Pocket Calculator”. The Japanese version is titled "Dentaku". Dentaku (電卓) is the Japanese name for a calculator.
At the time, Japanese calculators were at the peak of their evolution and it was not uncommon to find calculators with musical scales assigned to each button and the ability to play music.
I created this application to remember the old days and to make the tasteless task of calculation a little more enjoyable.
This application is not only a practical calculator, but also designed to be enjoyable to use.
Features:
• A musical scale is assigned to each button and between buttons, which produces a sound when operated. You can select from 200 different tones.
• The position of the scale can be checked using the 'Show Musical Scale' option.
C C# D D# E F F# G G# A A# B...
• You can choose your favorite background color. The background color changes according to the speed at which you tap the button. The faster you tap the button, the more the color changes. When you stop tapping, the color returns to the original color. What color it changes to depends on the original color. For example, a blue background turns reddish when a button is pressed repeatedly.
• If you switch on 'Auto Mode', the background color and tone will automatically change at random.
• You can name your favorite tone and background color combinations and save them in 'My Themes'.
• The basic calculation functions are generally the same specifications as those of the iOS calculator app, but there are some differences.
• Initially, the mode prioritizes multiplication and division. If this mode is switched off, the app behaves like a general Japanese calculator (except for scientific calculators).
• The optional RPN (Reverse Polish Notation) mode is a classic specification with a fixed number of stacks - the same specification as HP's 4-level RPN, but the number of stacks can be chosen between 4 and 8.
• Supports number formats for various countries.