Custom CSS Isn't recognized outside of index.hbl

I am basically combining my own static site files (HTML, CSS, JS) and the casper theme together. I’d love to use the casper theme for blog content and then use my own content for the Header/footer and static pages.

I have gotten my index.hbl page more or less how I want it, but I have tried editing my post.hbl with no luck. The HTML seems to take fine, but it isn’t recognizing my custom CSS files (like the index page is).

Any idea why this would be the case?

First of all the file extension is not .hbl, it’s .hbs
Don’t know what code is in your index.hbs file but normally any CSS or Js file inclusion goes into “default.hbs” file.

You should use {{asset}} helper to properly include any asset files ( CSS, JS etc. )

Check How `{{assets}}`` helper works here Ghost Handlebars Themes - Building a custom Ghost theme - Docs