Mine has a few other features like progression generators and some tools to show keyboard type instruments as well, but is lacking some of the neat things your tool has, like the pure chord visualizer.
Perhaps when I have some free time, I will try to contribute some progression building logic to your project.
I have a project with some similar features, written in Perl: https://github.com/whofferbert/key-mode
Mine has a few other features like progression generators and some tools to show keyboard type instruments as well, but is lacking some of the neat things your tool has, like the pure chord visualizer.
Perhaps when I have some free time, I will try to contribute some progression building logic to your project.