themes-wordpress/upsidedown/style.css

/*
Theme Name: Upsidedown
Theme URI: https://wordpress.com/theme/upsidedown/
Author: Automattic
Author URI: https://automattic.com/
Description: Upsidedown is a blog theme designed in the WordPress Site Editor. With its neat visuals, it introduces a direct experience on post reading: noticeable post titles listed on a text-only page, with an original swap of header and footer blocks.
Requires at least: 6.0
Tested up to: 6.1
Requires PHP: 5.7
Version: 1.0.3
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Template: 
Text Domain: upsidedown
Tags: one-column, custom-colors, custom-menu, custom-logo, editor-style, featured-images, full-site-editing, rtl-language-support, theme-options, threaded-comments, translation-ready, wide-blocks, blog, style-variations
*/

/*
 * Control the hover stylings of outline block style.
 * Unnecessary once block styles are configurable via theme.json
 * https://github.com/WordPress/gutenberg/issues/42794
 */
.wp-block-button.is-style-outline
	> .wp-block-button__link:not(.has-background):hover {
	background-color: var(--wp--preset--color--primary);
	color: var(--wp--preset--color--secondary);
	border-color: var(--wp--preset--color--primary);
}

/*
 * Link styles
 * https://github.com/WordPress/gutenberg/issues/42319
 */
a {
	text-decoration-thickness: 0.0625em !important;
	text-underline-offset: 0.15em;
}