That's exactly what I was doing.
Unzipped the folder, installed and activated parent theme, trying to upload a child theme and that's what happening.
Tried to download theme .zip archive again and unpacked it, still does the same. There is a style.css file in child .zip.
Unpacking the package…
Installing the theme…
The package could not be installed. The theme is missing the style.css stylesheet.
Theme installation failed.
Still don't get how this should work.
Right now when I'm trying to upload a child theme, it shows me error that style.css is missing.
It doesn't look like it's that simple as you describe in your demo and ads.
Let's say we made it to work. What happens when I do changes to CSS on child theme? Do I need to update the parent one as well?