Not able to find pre-defined sass variables in Jekyll project

Question

I'm new the Jeykll and Sass and have a quick question. Within the pre-built theme when starting a new project, where are these variables defined?

I can't seem to find them aware through out the build. This is in the _sass/layout.scss directory.

 */
.site-header {
    border-top: 5px solid $grey-color-dark;
    border-bottom: 1px solid $grey-color-light;
    min-height: 56px;

    // Positioning context for the mobile navigation icon
    position: relative;
}

.site-title {
    font-size: 26px;
    line-height: 56px;
    letter-spacing: -1px;
    margin-bottom: 0;
    float: left;

    &,
    &:visited {
        color: $grey-color-dark;
    }
}

.site-nav {
    float: right;
    line-height: 56px;

    .menu-icon {
        display: none;
    }

    .page-link {
        color: $text-color;
        line-height: $base-line-height;

        // Gaps between nav items, but not on the first one
        &:not(:first-child) {
            margin-left: 20px;
        }
    }

    @include media-query($on-palm) {
        position: absolute;
        top: 9px;
        right: 30px;
        background-color: $background-color;
        border: 1px solid $grey-color-light;
        border-radius: 5px;
        text-align: right;

        .menu-icon {
            display: block;
            float: right;
            width: 36px;
            height: 26px;
            line-height: 0;
            padding-top: 10px;
            text-align: center;

            > svg {
                width: 18px;
                height: 15px;

                path {
                    fill: $grey-color-dark;
                }
            }
        }

        .trigger {
            clear: both;
            display: none;
        }

        &:hover .trigger {
            display: block;
            padding-bottom: 5px;
        }

        .page-link {
            display: block;
            padding: 5px 10px;
        }
    }
}



/**
 * Site footer
 */
.site-footer {
    border-top: 1px solid $grey-color-light;
    padding: $spacing-unit 0;
}

.footer-heading {
    font-size: 18px;
    margin-bottom: $spacing-unit / 2;
}

.contact-list,
.social-media-list {
    list-style: none;
    margin-left: 0;
}

.footer-col-wrapper {
    font-size: 15px;
    color: $grey-color;
    margin-left: -$spacing-unit / 2;
    @extend %clearfix;
}

.footer-col {
    float: left;
    margin-bottom: $spacing-unit / 2;
    padding-left: $spacing-unit / 2;
}

.footer-col-1 {
    width: -webkit-calc(35% - (#{$spacing-unit} / 2));
    width:         calc(35% - (#{$spacing-unit} / 2));
}

.footer-col-2 {
    width: -webkit-calc(20% - (#{$spacing-unit} / 2));
    width:         calc(20% - (#{$spacing-unit} / 2));
}

.footer-col-3 {
    width: -webkit-calc(45% - (#{$spacing-unit} / 2));
    width:         calc(45% - (#{$spacing-unit} / 2));
}

@include media-query($on-laptop) {
    .footer-col-1,
    .footer-col-2 {
        width: -webkit-calc(50% - (#{$spacing-unit} / 2));
        width:         calc(50% - (#{$spacing-unit} / 2));
    }

    .footer-col-3 {
        width: -webkit-calc(100% - (#{$spacing-unit} / 2));
        width:         calc(100% - (#{$spacing-unit} / 2));
    }
}

@include media-query($on-palm) {
    .footer-col {
        float: none;
        width: -webkit-calc(100% - (#{$spacing-unit} / 2));
        width:         calc(100% - (#{$spacing-unit} / 2));
    }
}



/**
 * Page content
 */
.page-content {
    padding: $spacing-unit 0;
}

.page-heading {
    font-size: 20px;
}

.post-list {
    margin-left: 0;
    list-style: none;

    > li {
        margin-bottom: $spacing-unit;
    }
}

.post-meta {
    font-size: $small-font-size;
    color: $grey-color;
}

.post-link {
    display: block;
    font-size: 24px;
}



/**
 * Posts
 */
.post-header {
    margin-bottom: $spacing-unit;
}

.post-title {
    font-size: 42px;
    letter-spacing: -1px;
    line-height: 1;

    @include media-query($on-laptop) {
        font-size: 36px;
    }
}

.post-content {
    margin-bottom: $spacing-unit;

    h2 {
        font-size: 32px;

        @include media-query($on-laptop) {
            font-size: 28px;
        }
    }

    h3 {
        font-size: 26px;

        @include media-query($on-laptop) {
            font-size: 22px;
        }
    }

    h4 {
        font-size: 20px;

        @include media-query($on-laptop) {
            font-size: 18px;
        }
    }
}

Answer 1

Notice: Jekyll has since been updated, its default theme, minima, is now in a separate gem, and the definitions are there, in _sass/minima.scss.

---

Look at this, with relative path to site root in default Jekyl site css/main.scss. There they are. After all the definitions, imports and processing, there will be css/main.css in the resulting site.

Everything in _sass is just for importing into real assets that will be converted to CSS. The difference between Sass/SCSS files in _sass and everywhere else is that files from _sass are not compiled directly, but rather just lay where they are and wait to be imported. Every possibly reusable piece of Sass should be in _sass, that's what Sass partials and this system overall is designed for. This is especially useful if you use a lot of Sass libraries (like I do, and it's still a mess) and don't want them to be modified in order to be put into your assets.

All the other files (not in _sass), however, will be processed into corresponding *.css files, and in order to distinguish files for processing, Jekyll requires such files to have a YAML front-matter, usually empty.

---
---

// Sass code here

(I used to utilize Liquid for embedding variables in Sass, but that feature vanished after some updates, so now non-empty YFM in assets is of no use now).