To clarify, for the `.buy-button` class, is that where one should put super-specific styles like `margin-left: 12px`?
Also, is there a good place I can learn these kind of things? I'm a programmer trying to get better at CSS (SCSS now that we've setup the asset pipeline)—so far I've been reading random A List Apart and The Sass Way articles, but I feel like I could use a more holistic, in-depth understanding of CSS if there's a good book out there for that.
To answer your first question, yes that is exactly where you should put your super-specific styles. You want to put your communal styles in your placeholder, styles that all types have but are different in the mixin (background color, etc) and the rest on the class itself.
The best way to get better at Sass is to follow people who are active in the community (which unfortunately is not me). Start with Chris Coyier and Hampton Catlin and work your way from there.
If you don't mind me plugging my own talks, I have a few that are really good at learning Sass:
I would take a look at BEM. It's methodology and set of naming conventions to help write better, more modular and reusable CSS. It can take a while to get used to, and to get it right, but once you do it's a lifesaver. I can't imagine doing front-end dev without it now
I'm not a designer by any means, so take this with a grain of salt, but after reading through the first link, BEM bears a striking resemblance to hungarian notation, which I think most of us decided was a bad idea a long time ago. Do you have any sense that this naming convention is different somehow from the naming conventions that have been used and abandoned in other areas of software development, and if so, what makes it different?
Also, is there a good place I can learn these kind of things? I'm a programmer trying to get better at CSS (SCSS now that we've setup the asset pipeline)—so far I've been reading random A List Apart and The Sass Way articles, but I feel like I could use a more holistic, in-depth understanding of CSS if there's a good book out there for that.