 The first takeaway is that values can be inherited by descendants, but those descendants can't pass back values to their ancestors. Yep, that's a big one. Here's another takeaway. An invalid custom property value is unable to fall back to previously set cascaded value. Which is also why I really like registered custom properties, because you can set the fallback, so you don't run into that case and you foolproof your custom property systems, which are a big part of design systems. Also, just learn all about URLs and custom properties, so relative URLs are resolved to the directory they are found, which can be a remote directory. And then you already captured this takeaway, but use a fallback value when defining a custom property. That way, in case something happens, there's always a value there to be found.