What is the Opening Manager game, how does it work?

According to the introduction of Jonas Mayer, Opening Manager is a Board game on the Android platform. There is currently a 1.0 version released on Aug 30, 2017, you can see the details below.

Opening Manager is the notepad for your opening repertoire:

- Easily and quickly insert all your opening lines

- Found an interesting variation you want to try? Take a couple of seconds to add it to your opening and you won't forget about it.

- Crushed by a nasty gambit? Calm your frustration by expanding your arsenal with the correct follow up.

And finally:
To make sure you know all of your moves, test your memory in training.

New in 4.0:

- Browse an opening database powered by Lichess master games
- The Omniscient Knight: automatically find gaps in your repertoire
- UI improvements
- Bugfixes