This is the "Beta 2" version that was released from
September 2017 to December 2021.
The theme was 3D.

It uses a 3D library of 6 years ago, so on some modern machines,
It may result in an error that cannot be displayed. please note.

Why the emphasis was changed from 3D to 2D in version 1.0,
The details is written in Developer notes Release notes (1) .

Will 3D be the theme, even for versions 1.0 and later?
I would like to consider it if there is a request.