What is the Lock&Japanese: Learn Japanese basic words free application, how does it work?

According to the introduction of Boreumdal Lab., Lock&Japanese: Learn Japanese basic words free is a Education app on the Android platform. There is currently a 3.12.6 version released on Mar 18, 2020, you can see the details below.

Lock&Japanese is the best free app for learning Japanese.
It contains more than 3900 common Japanese words and phrases with excellent audio.

[ Features ]
- All contents are free
- Over 3900 commonly used words and phrases
- Many tests: Listening, Speaking, Writing, Sentence Completion etc.
- Simple user interface

[ Courses ]
- Hiragana, Katakana
- Basic words series
- Number, Calendar, Time
- Absolute Beginer
- Japanese for travelers
- Situational Japanese
- Love-related words
...