Working with Configurable Variables

There are two ways of defining a variable in Sass. The first, most common, approach is simple assignment. For example:

$my-constant : #fedcba

The second approach is called guarded assignment. In this case, the constant is only set if it does not already have a value. For example:

$my-constant : #fedcba !default

Many compass modules use guarded assignment to allow you to set defaults for that module. In order for these configurable variables to work correctly, you must set the variables before you import the module. For example:

$blueprint-grid-columns = 12
@import "blueprint/grid"

Because of this, it is common to have one or more partials that set the constants first and get imported before any other imports in your stylesheet(s). This is commonly referred to as the "base" stylesheet and is usually named _base.scss or _base.sass.