diff --git a/backport-changelog/6.6/7145.md b/backport-changelog/6.6/7145.md
new file mode 100644
index 0000000000000..386f765cb22fa
--- /dev/null
+++ b/backport-changelog/6.6/7145.md
@@ -0,0 +1,3 @@
+https://github.com/WordPress/wordpress-develop/pull/7145
+
+* https://github.com/WordPress/gutenberg/pull/64076
diff --git a/lib/class-wp-theme-json-gutenberg.php b/lib/class-wp-theme-json-gutenberg.php
index cfe0c4d55ceed..f4c4a12e3e4ca 100644
--- a/lib/class-wp-theme-json-gutenberg.php
+++ b/lib/class-wp-theme-json-gutenberg.php
@@ -1744,7 +1744,7 @@ protected function get_layout_styles( $block_metadata, $types = array() ) {
 										$spacing_rule['selector']
 									);
 								} else {
-									$format          = static::ROOT_BLOCK_SELECTOR === $selector ? '.%2$s %3$s' : '%1$s-%2$s %3$s';
+									$format          = static::ROOT_BLOCK_SELECTOR === $selector ? ':root :where(.%2$s)%3$s' : ':root :where(%1$s-%2$s)%3$s';
 									$layout_selector = sprintf(
 										$format,
 										$selector,
diff --git a/packages/block-editor/src/components/global-styles/test/use-global-styles-output.js b/packages/block-editor/src/components/global-styles/test/use-global-styles-output.js
index 3f7fb5462e377..a98bdb6129da8 100644
--- a/packages/block-editor/src/components/global-styles/test/use-global-styles-output.js
+++ b/packages/block-editor/src/components/global-styles/test/use-global-styles-output.js
@@ -763,7 +763,7 @@ describe( 'global styles renderer', () => {
 			} );
 
 			expect( layoutStyles ).toEqual(
-				'.is-layout-flow > * { margin-block-start: 0; margin-block-end: 0; }.is-layout-flow > * + * { margin-block-start: 0.5em; margin-block-end: 0; }.is-layout-flex { gap: 0.5em; }:root { --wp--style--block-gap: 0.5em; }.is-layout-flow > .alignleft { float: left; margin-inline-start: 0; margin-inline-end: 2em; }.is-layout-flow > .alignright { float: right; margin-inline-start: 2em; margin-inline-end: 0; }.is-layout-flow > .aligncenter { margin-left: auto !important; margin-right: auto !important; }body .is-layout-flex { display:flex; }.is-layout-flex { flex-wrap: wrap; align-items: center; }.is-layout-flex > * { margin: 0; }'
+				':root :where(.is-layout-flow) > * { margin-block-start: 0; margin-block-end: 0; }:root :where(.is-layout-flow) > * + * { margin-block-start: 0.5em; margin-block-end: 0; }:root :where(.is-layout-flex) { gap: 0.5em; }:root { --wp--style--block-gap: 0.5em; }.is-layout-flow > .alignleft { float: left; margin-inline-start: 0; margin-inline-end: 2em; }.is-layout-flow > .alignright { float: right; margin-inline-start: 2em; margin-inline-end: 0; }.is-layout-flow > .aligncenter { margin-left: auto !important; margin-right: auto !important; }body .is-layout-flex { display:flex; }.is-layout-flex { flex-wrap: wrap; align-items: center; }.is-layout-flex > * { margin: 0; }'
 			);
 		} );
 
@@ -780,7 +780,7 @@ describe( 'global styles renderer', () => {
 			} );
 
 			expect( layoutStyles ).toEqual(
-				'.is-layout-flow > * { margin-block-start: 0; margin-block-end: 0; }.is-layout-flow > * + * { margin-block-start: 12px; margin-block-end: 0; }.is-layout-flex { gap: 12px; }:root { --wp--style--block-gap: 12px; }.is-layout-flow > .alignleft { float: left; margin-inline-start: 0; margin-inline-end: 2em; }.is-layout-flow > .alignright { float: right; margin-inline-start: 2em; margin-inline-end: 0; }.is-layout-flow > .aligncenter { margin-left: auto !important; margin-right: auto !important; }body .is-layout-flex { display:flex; }.is-layout-flex { flex-wrap: wrap; align-items: center; }.is-layout-flex > * { margin: 0; }'
+				':root :where(.is-layout-flow) > * { margin-block-start: 0; margin-block-end: 0; }:root :where(.is-layout-flow) > * + * { margin-block-start: 12px; margin-block-end: 0; }:root :where(.is-layout-flex) { gap: 12px; }:root { --wp--style--block-gap: 12px; }.is-layout-flow > .alignleft { float: left; margin-inline-start: 0; margin-inline-end: 2em; }.is-layout-flow > .alignright { float: right; margin-inline-start: 2em; margin-inline-end: 0; }.is-layout-flow > .aligncenter { margin-left: auto !important; margin-right: auto !important; }body .is-layout-flex { display:flex; }.is-layout-flex { flex-wrap: wrap; align-items: center; }.is-layout-flex > * { margin: 0; }'
 			);
 		} );
 
@@ -797,7 +797,7 @@ describe( 'global styles renderer', () => {
 			} );
 
 			expect( layoutStyles ).toEqual(
-				'.wp-block-group-is-layout-flow > * { margin-block-start: 0; margin-block-end: 0; }.wp-block-group-is-layout-flow > * + * { margin-block-start: 12px; margin-block-end: 0; }.wp-block-group-is-layout-flex { gap: 12px; }'
+				':root :where(.wp-block-group-is-layout-flow) > * { margin-block-start: 0; margin-block-end: 0; }:root :where(.wp-block-group-is-layout-flow) > * + * { margin-block-start: 12px; margin-block-end: 0; }:root :where(.wp-block-group-is-layout-flex) { gap: 12px; }'
 			);
 		} );
 
diff --git a/packages/block-editor/src/components/global-styles/use-global-styles-output.js b/packages/block-editor/src/components/global-styles/use-global-styles-output.js
index 6d3e29f360200..dc82b578c2161 100644
--- a/packages/block-editor/src/components/global-styles/use-global-styles-output.js
+++ b/packages/block-editor/src/components/global-styles/use-global-styles-output.js
@@ -538,10 +538,10 @@ export function getLayoutStyles( {
 							} else {
 								combinedSelector =
 									selector === ROOT_BLOCK_SELECTOR
-										? `.${ className }${
+										? `:root :where(.${ className })${
 												spacingStyle?.selector || ''
 										  }`
-										: `${ selector }-${ className }${
+										: `:root :where(${ selector }-${ className })${
 												spacingStyle?.selector || ''
 										  }`;
 							}
diff --git a/phpunit/class-wp-theme-json-test.php b/phpunit/class-wp-theme-json-test.php
index 8d2f470efe60f..510fad367a69a 100644
--- a/phpunit/class-wp-theme-json-test.php
+++ b/phpunit/class-wp-theme-json-test.php
@@ -714,7 +714,7 @@ public function test_get_stylesheet_renders_enabled_protected_properties() {
 			)
 		);
 
-		$expected = ':where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: 1em; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1em; }.is-layout-flow  > :first-child{margin-block-start: 0;}.is-layout-flow  > :last-child{margin-block-end: 0;}.is-layout-flow  > *{margin-block-start: 1em;margin-block-end: 0;}.is-layout-constrained  > :first-child{margin-block-start: 0;}.is-layout-constrained  > :last-child{margin-block-end: 0;}.is-layout-constrained  > *{margin-block-start: 1em;margin-block-end: 0;}.is-layout-flex {gap: 1em;}.is-layout-grid {gap: 1em;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){margin-left: auto !important;margin-right: auto !important;}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}';
+		$expected = ':where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: 1em; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1em; }:root :where(.is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.is-layout-flow) > *{margin-block-start: 1em;margin-block-end: 0;}:root :where(.is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.is-layout-constrained) > *{margin-block-start: 1em;margin-block-end: 0;}:root :where(.is-layout-flex){gap: 1em;}:root :where(.is-layout-grid){gap: 1em;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){margin-left: auto !important;margin-right: auto !important;}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}';
 		$this->assertSameCSS( $expected, $theme_json->get_stylesheet() );
 		$this->assertSameCSS( $expected, $theme_json->get_stylesheet( array( 'styles' ) ) );
 	}
@@ -1131,7 +1131,7 @@ public function test_get_stylesheet_generates_layout_styles() {
 
 		// Results also include root site blocks styles.
 		$this->assertSameCSS(
-			':root { --wp--style--global--content-size: 640px;--wp--style--global--wide-size: 1200px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: 1em; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1em; }.is-layout-flow  > :first-child{margin-block-start: 0;}.is-layout-flow  > :last-child{margin-block-end: 0;}.is-layout-flow  > *{margin-block-start: 1em;margin-block-end: 0;}.is-layout-constrained  > :first-child{margin-block-start: 0;}.is-layout-constrained  > :last-child{margin-block-end: 0;}.is-layout-constrained  > *{margin-block-start: 1em;margin-block-end: 0;}.is-layout-flex {gap: 1em;}.is-layout-grid {gap: 1em;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}',
+			':root { --wp--style--global--content-size: 640px;--wp--style--global--wide-size: 1200px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: 1em; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1em; }:root :where(.is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.is-layout-flow) > *{margin-block-start: 1em;margin-block-end: 0;}:root :where(.is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.is-layout-constrained) > *{margin-block-start: 1em;margin-block-end: 0;}:root :where(.is-layout-flex){gap: 1em;}:root :where(.is-layout-grid){gap: 1em;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}',
 			$theme_json->get_stylesheet( array( 'styles' ) )
 		);
 	}
@@ -1160,7 +1160,7 @@ public function test_get_stylesheet_generates_layout_styles_with_spacing_presets
 
 		// Results also include root site blocks styles.
 		$this->assertSameCSS(
-			':root { --wp--style--global--content-size: 640px;--wp--style--global--wide-size: 1200px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: var(--wp--preset--spacing--60); margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: var(--wp--preset--spacing--60); }.is-layout-flow  > :first-child{margin-block-start: 0;}.is-layout-flow  > :last-child{margin-block-end: 0;}.is-layout-flow  > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}.is-layout-constrained  > :first-child{margin-block-start: 0;}.is-layout-constrained  > :last-child{margin-block-end: 0;}.is-layout-constrained  > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}.is-layout-flex {gap: var(--wp--preset--spacing--60);}.is-layout-grid {gap: var(--wp--preset--spacing--60);}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}',
+			':root { --wp--style--global--content-size: 640px;--wp--style--global--wide-size: 1200px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: var(--wp--preset--spacing--60); margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: var(--wp--preset--spacing--60); }:root :where(.is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.is-layout-flow) > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}:root :where(.is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.is-layout-constrained) > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}:root :where(.is-layout-flex){gap: var(--wp--preset--spacing--60);}:root :where(.is-layout-grid){gap: var(--wp--preset--spacing--60);}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}',
 			$theme_json->get_stylesheet( array( 'styles' ) )
 		);
 	}
@@ -1284,8 +1284,7 @@ public function test_get_stylesheet_generates_valid_block_gap_values_and_skips_n
 		);
 
 		$this->assertSameCSS(
-			':root { --wp--style--global--content-size: 640px;--wp--style--global--wide-size: 1200px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: 1rem; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1rem; }.is-layout-flow  > :first-child{margin-block-start: 0;}.is-layout-flow  > :last-child{margin-block-end: 0;}.is-layout-flow  > *{margin-block-start: 1rem;margin-block-end: 0;}.is-layout-constrained  > :first-child{margin-block-start: 0;}.is-layout-constrained  > :last-child{margin-block-end: 0;}.is-layout-constrained  > *{margin-block-start: 1rem;margin-block-end: 0;}.is-layout-flex {gap: 1rem;}.is-layout-grid {gap: 1rem;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}' .
-			':root :where(.wp-block-post-content){color: gray;}.wp-block-social-links-is-layout-flow  > :first-child{margin-block-start: 0;}.wp-block-social-links-is-layout-flow  > :last-child{margin-block-end: 0;}.wp-block-social-links-is-layout-flow  > *{margin-block-start: 0;margin-block-end: 0;}.wp-block-social-links-is-layout-constrained  > :first-child{margin-block-start: 0;}.wp-block-social-links-is-layout-constrained  > :last-child{margin-block-end: 0;}.wp-block-social-links-is-layout-constrained  > *{margin-block-start: 0;margin-block-end: 0;}.wp-block-social-links-is-layout-flex {gap: 0;}.wp-block-social-links-is-layout-grid {gap: 0;}.wp-block-buttons-is-layout-flow  > :first-child{margin-block-start: 0;}.wp-block-buttons-is-layout-flow  > :last-child{margin-block-end: 0;}.wp-block-buttons-is-layout-flow  > *{margin-block-start: 0;margin-block-end: 0;}.wp-block-buttons-is-layout-constrained  > :first-child{margin-block-start: 0;}.wp-block-buttons-is-layout-constrained  > :last-child{margin-block-end: 0;}.wp-block-buttons-is-layout-constrained  > *{margin-block-start: 0;margin-block-end: 0;}.wp-block-buttons-is-layout-flex {gap: 0;}.wp-block-buttons-is-layout-grid {gap: 0;}',
+			':root { --wp--style--global--content-size: 640px;--wp--style--global--wide-size: 1200px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: 1rem; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1rem; }:root :where(.is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.is-layout-flow) > *{margin-block-start: 1rem;margin-block-end: 0;}:root :where(.is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.is-layout-constrained) > *{margin-block-start: 1rem;margin-block-end: 0;}:root :where(.is-layout-flex){gap: 1rem;}:root :where(.is-layout-grid){gap: 1rem;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}:root :where(.wp-block-post-content){color: gray;}:root :where(.wp-block-social-links-is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.wp-block-social-links-is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.wp-block-social-links-is-layout-flow) > *{margin-block-start: 0;margin-block-end: 0;}:root :where(.wp-block-social-links-is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.wp-block-social-links-is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.wp-block-social-links-is-layout-constrained) > *{margin-block-start: 0;margin-block-end: 0;}:root :where(.wp-block-social-links-is-layout-flex){gap: 0;}:root :where(.wp-block-social-links-is-layout-grid){gap: 0;}:root :where(.wp-block-buttons-is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.wp-block-buttons-is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.wp-block-buttons-is-layout-flow) > *{margin-block-start: 0;margin-block-end: 0;}:root :where(.wp-block-buttons-is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.wp-block-buttons-is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.wp-block-buttons-is-layout-constrained) > *{margin-block-start: 0;margin-block-end: 0;}:root :where(.wp-block-buttons-is-layout-flex){gap: 0;}:root :where(.wp-block-buttons-is-layout-grid){gap: 0;}',
 			$theme_json->get_stylesheet()
 		);
 	}
@@ -3690,7 +3689,7 @@ public function test_get_styles_with_appearance_tools() {
 			'selector' => 'body',
 		);
 
-		$expected = ':where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: ; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: ; }.is-layout-flow  > :first-child{margin-block-start: 0;}.is-layout-flow  > :last-child{margin-block-end: 0;}.is-layout-flow  > *{margin-block-start: 1;margin-block-end: 0;}.is-layout-constrained  > :first-child{margin-block-start: 0;}.is-layout-constrained  > :last-child{margin-block-end: 0;}.is-layout-constrained  > *{margin-block-start: 1;margin-block-end: 0;}.is-layout-flex {gap: 1;}.is-layout-grid {gap: 1;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){margin-left: auto !important;margin-right: auto !important;}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}';
+		$expected = ':where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.wp-site-blocks) > * { margin-block-start: ; margin-block-end: 0; }:where(.wp-site-blocks) > :first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child { margin-block-end: 0; }:root { --wp--style--block-gap: ; }:root :where(.is-layout-flow) > :first-child{margin-block-start: 0;}:root :where(.is-layout-flow) > :last-child{margin-block-end: 0;}:root :where(.is-layout-flow) > *{margin-block-start: 1;margin-block-end: 0;}:root :where(.is-layout-constrained) > :first-child{margin-block-start: 0;}:root :where(.is-layout-constrained) > :last-child{margin-block-end: 0;}:root :where(.is-layout-constrained) > *{margin-block-start: 1;margin-block-end: 0;}:root :where(.is-layout-flex){gap: 1;}:root :where(.is-layout-grid){gap: 1;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){margin-left: auto !important;margin-right: auto !important;}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}';
 		$this->assertSameCSS( $expected, $theme_json->get_root_layout_rules( WP_Theme_JSON_Gutenberg::ROOT_BLOCK_SELECTOR, $metadata ) );
 	}