Settings is basically a set of variables that the underlying layers are using. All the variables have got default set values. It's marked !default so that the preprocessor build, will say this: "If no other value is set to this variable by now, this is what it'll get."

Base variables (base.scss)

Layout (base.layout.scss)

Colors (base.colors.scss)

Generic (generic.scss)

Design (

Elements (elements.scss)

Typography.scss (elements.typography.scss)

Objects (objects.scss)

Grid objects.typography.scss