WordPress/wp-content/themes/twentytwentyone/assets/sass/03-generic/vertical-margins.scss

/**
 * Site Structure
 *
 * - Set vertical margins and responsive widths on
 *   top-level wrappers and content wrappers
 * - `--global--width-content` is a responsive variable
 * - See: globals/_global-width-responsive.scss
 */

/**
 * Top Level Wrappers (header, main, footer)
 * - Set vertical padding and horizontal margins
 */
.site-header,
.site-main,
.widget-area,
.site-footer {
	padding-top: var(--global--spacing-vertical);
	padding-bottom: var(--global--spacing-vertical);
	margin-left: auto;
	margin-right: auto;
}

.site-header {
	padding-top: calc(0.75 * var(--global--spacing-vertical));
	padding-bottom: calc(2 * var(--global--spacing-vertical));

	@include media(mobile) {
		padding-bottom: calc(3 * var(--global--spacing-vertical));
	}
}

/**
 * Site-main children wrappers
 * - Add double vertical margins here for clearer hierarchy
 */
.site-main > * {
	margin-top: calc(3 * var(--global--spacing-vertical));
	margin-bottom: calc(3 * var(--global--spacing-vertical));

	&:first-child {
		margin-top: 0;
	}

	&:last-child {
		margin-bottom: 0;
	}
}

/**
 * Set the default maximum responsive content-width
 */
.default-max-width {
	@extend %responsive-aligndefault-width;
}

/**
 * Set the wide maximum responsive content-width
 */
.wide-max-width {
	@extend %responsive-alignwide-width;
}

/**
 * Set the full maximum responsive content-width
 */
.full-max-width {
	@extend %responsive-alignfull-width-mobile;
	@extend %responsive-alignfull-width;
}

/*
 * Block & non-gutenberg content wrappers
 * - Set margins
 */
.entry-header,
.post-thumbnail,
.entry-content,
.entry-footer,
.author-bio {
	margin-top: var(--global--spacing-vertical);
	margin-right: auto;
	margin-bottom: var(--global--spacing-vertical);
	margin-left: auto;
}

/*
 * Block & non-gutenberg content wrapper children
 * - Sets spacing-vertical margin logic
 */
.site-main > article > *, // apply vertical margins to article level
.site-main > .not-found > *, // apply vertical margins to article level
.entry-content > *,
[class*="inner-container"] > *,
.wp-block-template-part > * {

	margin-top: calc(0.666 * var(--global--spacing-vertical));
	margin-bottom: calc(0.666 * var(--global--spacing-vertical));

	@include media(mobile) {
		margin-top: var(--global--spacing-vertical);
		margin-bottom: var(--global--spacing-vertical);
	}

	&:first-child {
		margin-top: 0;
	}

	&:last-child {
		margin-bottom: 0;
	}
}

.site-footer > *,
.widget-area > * {
	margin-top: calc(0.666 * var(--global--spacing-vertical));
	margin-bottom: calc(0.666 * var(--global--spacing-vertical));

	@include media(mobile) {
		margin-top: var(--global--spacing-vertical);
		margin-bottom: var(--global--spacing-vertical);
	}
}

/*
 * Block & non-gutenberg content wrapper children
 * - Sets spacing-unit margins
 */
//.site-header > *, // Removed, to align site title and menu.
.entry-header > *,
.post-thumbnail > *,
.page-content > *,
.comment-content > *,
.widget > * {
	margin-top: var(--global--spacing-unit);
	margin-bottom: var(--global--spacing-unit);

	&:first-child {
		margin-top: 0;
	}

	&:last-child {
		margin-bottom: 0;
	}
}


/*
 * .entry-content children specific controls
 * - Adds special margin overrides for alignment utility classes
 */
.entry-content > * {

	&.alignleft,
	&.alignright,
	&.alignleft:first-child + *,
	&.alignright:first-child + *,
	&.alignfull.has-background {
		margin-top: 0;
	}

	&:last-child,
	&.alignfull.has-background {
		margin-bottom: 0;
	}

	/* Reset alignleft and alignright margins after alignfull */
	&.alignfull + .alignleft,
	&.alignfull + .alignright {
		margin-top: var(--global--spacing-vertical);
	}
}