How to put button in the corner of the screen?

Nice :+1:

Since you mentioned that you already have ruby files, I’m guessing that you’re working on a plugin, right?

So, to answer your question

I would recommend that you look at the folder structure of some of our existing official plugins like this one

https://github.com/discourse/discourse-math

or this one

https://github.com/discourse/discourse-assign

If you look at those, you’ll notice that the SCSS stylesheets are always placed in

_ROOT_/assets/stylesheets/

and that’s where your SCSS files should go if you’re making a plugin.