css-mastery-16-master/cssmastery-examples/chapter-12/workflow-project/main.scss

@import 'library';

body {
    color: $primary-color;
    background-color: darken($secondary-color, 10%);
}
%inverted {
    color: $secondary-color;
    background-color: $primary-color;
    @include font-smoothing;
}
.page-header {
    @extend %inverted;
    display: flex;
}
.page-footer {
    @extend %inverted;
    background-color: #14203B;
    a {
        color: darken(#fff, 10%);
    }
}