Offline CSS Validator?

Does anyone know of a CSS Validator that works without an Internet connection? Everything I've found seems to require a live Internet connection to access W3C.

I did find this page, which has command-line instructions. The instructions are a little over my head and I couldn't get it to work, but it seems you still need an Internect connection: https://jigsaw.w3.org/css-validator/DOWNLOAD.html

Thanks for any help!