7.4 Partials and modules

7.4.1 Why

• Make CSS composable rather than monolithic
• Capture one set of rules in one file (e.g., fonts, helpers, etc.)
• Compose a main Sass file that imports partials/modules as needed

7.4.2 How

• Create a files that start with _. Sass will recognize them as partials.
• Import them with the @import directive. (Update: Sass says to use @use instead, since @import may be deprecated.)

See evocative example in the book.