I very often see the pretense of something like "writing is not language" which I still don't quite understand. As I understand, writing is a representation of a language, but not the language itself, thus it's not a part of it. But isn't phonology about how the language is represented, but instead of hearing matter, visually? Yes, phonology impacts the way you perceive language. But writing also does this. It's especially evident in Japanese, where words could be indistinguishable orally but are written differently.
And language can exist without being spoken. Sign language is an obvious example. I know there is its own "phonetics", but aren't its phonetics very different from the usual definition of phonetics? Even the one on this website includes "sound" in the definition. If you need to stretch a meaning of a word so far, I'm sure you could call a part of writing "phonetics"
Sorry if it's a dumb question and everything above is dumb, I'm really not well-educated in Linguistics and just trying to figure it out. If there's some literature that would help me to understand this topic I would love to check it out.