Documentation for Vigenère cipher has been added

The app makes it possible to encrypt messages using Vigenère cipher. Because I have received multiple questions how does it work, I have added a detailed description of the particular version of Vigenère cipher used in the app. You will learn there the why it has been chosen for the app, its pros and cons, and how exactly it works.

Version 7.0 released

There are two main changes in the release:

• There is a new slider in the settings that you can use to customize the amount of the noise added to the sound. You can try using small values to fix problems with some Bluetooth headphones. The higher values can be used to simulate a radio distortion.
• It was changed how time is measured in the learning for listening exercises. For this mode, the time is measured from the moment the playing has finished (it was measured from the beginning of the sound in the previous version, which was not correct). There has been no change for normal mode and silent mode - the time is measured from the moment the code is displayed on the screen.

As usual, there are also plenty of small improvements and bug fixes.