They show the current state of the development and are work-in-progress.
While they contain more content than the demo. Although, not every feature or level is finalised. There might be bugs, including show-stoppers.
The preview builds can be accessed for free.
where to get them?
There are two ways to get a preview build.
You can download and sideload the preview build:
Alternatively, you can contact me (firstname.lastname@example.org) and I can add you to the preview channel on AppLab. This way you will automatically get the latest preview builds.
The preview builds are not available through any distribution platform on PC yet. Simply download and unpack the preview build: