diff --git a/lib/class-wp-theme-json-gutenberg.php b/lib/class-wp-theme-json-gutenberg.php
index df10ddcd6e684..d555333dd1b3a 100644
--- a/lib/class-wp-theme-json-gutenberg.php
+++ b/lib/class-wp-theme-json-gutenberg.php
@@ -2705,8 +2705,8 @@ public function get_root_layout_rules( $selector, $block_metadata ) {
 		}
 
 		/*
-		* Reset default browser margin on the root body element.
-		* This is set on the root selector **before** generating the ruleset
+		* Reset default browser margin on the body element.
+		* This is set on the body selector **before** generating the ruleset
 		* from the `theme.json`. This is to ensure that if the `theme.json` declares
 		* `margin` in its `spacing` declaration for the `body` element then these
 		* user-generated values take precedence in the CSS cascade.
@@ -2744,7 +2744,7 @@ public function get_root_layout_rules( $selector, $block_metadata ) {
 			$css            .= ':where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }';
 
 			// For backwards compatibility, ensure the legacy block gap CSS variable is still available.
-				$css .= static::ROOT_CSS_PROPERTIES_SELECTOR . " { --wp--style--block-gap: $block_gap_value; }";
+			$css .= static::ROOT_CSS_PROPERTIES_SELECTOR . " { --wp--style--block-gap: $block_gap_value; }";
 		}
 		$css .= $this->get_layout_styles( $block_metadata );
 
diff --git a/phpunit/class-wp-theme-json-test.php b/phpunit/class-wp-theme-json-test.php
index 09e0e9880664c..fc61acd7ff0a6 100644
--- a/phpunit/class-wp-theme-json-test.php
+++ b/phpunit/class-wp-theme-json-test.php
@@ -552,7 +552,7 @@ public function test_get_stylesheet() {
 			)
 		);
 
-		$variables = 'body{--wp--preset--color--grey: grey;--wp--preset--gradient--custom-gradient: linear-gradient(135deg,rgba(0,0,0) 0%,rgb(0,0,0) 100%);--wp--preset--font-size--small: 14px;--wp--preset--font-size--big: 41px;--wp--preset--font-family--arial: Arial, serif;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}';
+		$variables = ':root{--wp--preset--color--grey: grey;--wp--preset--gradient--custom-gradient: linear-gradient(135deg,rgba(0,0,0) 0%,rgb(0,0,0) 100%);--wp--preset--font-size--small: 14px;--wp--preset--font-size--big: 41px;--wp--preset--font-family--arial: Arial, serif;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}';
 		$styles    = static::$base_styles . 'body{color: var(--wp--preset--color--grey);}a:where(:not(.wp-element-button)){background-color: #333;color: #111;}.wp-element-button, .wp-block-button__link{box-shadow: 10px 10px 5px 0px rgba(0,0,0,0.66);}.wp-block-cover{min-height: unset;aspect-ratio: 16/9;}.wp-block-group{background: var(--wp--preset--gradient--custom-gradient);border-radius: 10px;min-height: 50vh;padding: 24px;}.wp-block-group a:where(:not(.wp-element-button)){color: #111;}.wp-block-heading{color: #123456;}.wp-block-heading a:where(:not(.wp-element-button)){background-color: #333;color: #111;font-size: 60px;}.wp-block-post-date{color: #123456;}.wp-block-post-date a:where(:not(.wp-element-button)){background-color: #777;color: #555;}.wp-block-post-excerpt{column-count: 2;}.wp-block-image{margin-bottom: 30px;}.wp-block-image img, .wp-block-image .wp-block-image__crop-area, .wp-block-image .components-placeholder{border-top-left-radius: 10px;border-bottom-right-radius: 1em;}.wp-block-image img, .wp-block-image .components-placeholder{filter: var(--wp--preset--duotone--custom-duotone);}';
 		$presets   = '.has-grey-color{color: var(--wp--preset--color--grey) !important;}.has-grey-background-color{background-color: var(--wp--preset--color--grey) !important;}.has-grey-border-color{border-color: var(--wp--preset--color--grey) !important;}.has-custom-gradient-gradient-background{background: var(--wp--preset--gradient--custom-gradient) !important;}.has-small-font-size{font-size: var(--wp--preset--font-size--small) !important;}.has-big-font-size{font-size: var(--wp--preset--font-size--big) !important;}.has-arial-font-family{font-family: var(--wp--preset--font-family--arial) !important;}';
 		$all       = $variables . $styles . $presets;
@@ -650,7 +650,7 @@ public function test_get_stylesheet_renders_enabled_protected_properties() {
 			)
 		);
 
-		$expected = '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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }body { --wp--style--block-gap: 1em; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1em;}:where(body .is-layout-grid) {gap: 1em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}';
+		$expected = '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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1em; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1em;}:where(body .is-layout-grid) {gap: 1em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}';
 		$this->assertSame( $expected, $theme_json->get_stylesheet() );
 		$this->assertSame( $expected, $theme_json->get_stylesheet( array( 'styles' ) ) );
 	}
@@ -761,7 +761,7 @@ public function test_get_stylesheet_generates_proper_classes_and_css_vars_from_s
 			$theme_json->get_stylesheet( array( 'presets' ) )
 		);
 		$this->assertSame(
-			'body{--wp--preset--color--grey: grey;--wp--preset--color--dark-grey: grey;--wp--preset--color--light-grey: grey;--wp--preset--color--white-2-black: grey;--wp--custom--white-2-black: value;}',
+			':root{--wp--preset--color--grey: grey;--wp--preset--color--dark-grey: grey;--wp--preset--color--light-grey: grey;--wp--preset--color--white-2-black: grey;--wp--custom--white-2-black: value;}',
 			$theme_json->get_stylesheet( array( 'variables' ) )
 		);
 	}
@@ -799,7 +799,7 @@ public function test_get_stylesheet_preset_values_are_marked_as_important() {
 		);
 
 		$this->assertSame(
-			'body{--wp--preset--color--grey: grey;}' . static::$base_styles . 'p{background-color: blue;color: red;font-size: 12px;line-height: 1.3;}.has-grey-color{color: var(--wp--preset--color--grey) !important;}.has-grey-background-color{background-color: var(--wp--preset--color--grey) !important;}.has-grey-border-color{border-color: var(--wp--preset--color--grey) !important;}',
+			':root{--wp--preset--color--grey: grey;}' . static::$base_styles . 'p{background-color: blue;color: red;font-size: 12px;line-height: 1.3;}.has-grey-color{color: var(--wp--preset--color--grey) !important;}.has-grey-background-color{background-color: var(--wp--preset--color--grey) !important;}.has-grey-border-color{border-color: var(--wp--preset--color--grey) !important;}',
 			$theme_json->get_stylesheet()
 		);
 	}
@@ -1100,7 +1100,7 @@ public function test_get_stylesheet_with_deprecated_feature_level_selectors() {
 			)
 		);
 
-		$base_styles   = 'body{--wp--preset--color--green: green;}' . static::$base_styles;
+		$base_styles   = ':root{--wp--preset--color--green: green;}' . static::$base_styles;
 		$block_styles  = '.wp-block-test, .wp-block-test__wrapper{color: green;}.wp-block-test .inner, .wp-block-test__wrapper .inner{border-radius: 9999px;padding: 20px;}.wp-block-test .sub-heading, .wp-block-test__wrapper .sub-heading{font-size: 3em;}';
 		$preset_styles = '.has-green-color{color: var(--wp--preset--color--green) !important;}.has-green-background-color{background-color: var(--wp--preset--color--green) !important;}.has-green-border-color{border-color: var(--wp--preset--color--green) !important;}';
 		$expected      = $base_styles . $block_styles . $preset_styles;
@@ -1162,7 +1162,7 @@ public function test_get_stylesheet_with_block_json_selectors() {
 			)
 		);
 
-		$base_styles   = 'body{--wp--preset--color--green: green;}' . static::$base_styles;
+		$base_styles   = ':root{--wp--preset--color--green: green;}' . static::$base_styles;
 		$block_styles  = '.custom-root-selector{background-color: grey;padding: 20px;}.custom-root-selector img{border-radius: 9999px;}.custom-root-selector > figcaption{color: navy;font-size: 3em;}';
 		$preset_styles = '.has-green-color{color: var(--wp--preset--color--green) !important;}.has-green-background-color{background-color: var(--wp--preset--color--green) !important;}.has-green-border-color{border-color: var(--wp--preset--color--green) !important;}';
 		$expected      = $base_styles . $block_styles . $preset_styles;
@@ -1190,7 +1190,7 @@ public function test_get_stylesheet_generates_layout_styles() {
 
 		// Results also include root site blocks styles.
 		$this->assertSame(
-			'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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }body { --wp--style--block-gap: 1em; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1em;}:where(body .is-layout-grid) {gap: 1em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}',
+			'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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1em; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1em;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1em;}:where(body .is-layout-grid) {gap: 1em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}',
 			$theme_json->get_stylesheet( array( 'styles' ) )
 		);
 	}
@@ -1215,7 +1215,7 @@ public function test_get_stylesheet_generates_layout_styles_with_spacing_presets
 
 		// Results also include root site blocks styles.
 		$this->assertSame(
-			'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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }body { --wp--style--block-gap: var(--wp--preset--spacing--60); }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}:where(body .is-layout-flex) {gap: var(--wp--preset--spacing--60);}:where(body .is-layout-grid) {gap: var(--wp--preset--spacing--60);}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}',
+			'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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }:root { --wp--style--block-gap: var(--wp--preset--spacing--60); }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: var(--wp--preset--spacing--60);margin-block-end: 0;}:where(body .is-layout-flex) {gap: var(--wp--preset--spacing--60);}:where(body .is-layout-grid) {gap: var(--wp--preset--spacing--60);}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}',
 			$theme_json->get_stylesheet( array( 'styles' ) )
 		);
 	}
@@ -1331,7 +1331,7 @@ public function test_get_stylesheet_generates_valid_block_gap_values_and_skips_n
 		);
 
 		$this->assertSame(
-			'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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }body { --wp--style--block-gap: 1rem; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1rem;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1rem;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1rem;}:where(body .is-layout-grid) {gap: 1rem;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}' .
+			'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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }:root { --wp--style--block-gap: 1rem; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1rem;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1rem;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1rem;}:where(body .is-layout-grid) {gap: 1rem;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}' .
 			'.wp-block-post-content{color: gray;}.wp-block-social-links-is-layout-flow > :first-child:first-child{margin-block-start: 0;}.wp-block-social-links-is-layout-flow > :last-child: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:first-child{margin-block-start: 0;}.wp-block-social-links-is-layout-constrained > :last-child: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:first-child{margin-block-start: 0;}.wp-block-buttons-is-layout-flow > :last-child: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:first-child{margin-block-start: 0;}.wp-block-buttons-is-layout-constrained > :last-child: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;}',
 			$theme_json->get_stylesheet()
 		);
@@ -1448,7 +1448,7 @@ public function test_get_stylesheet_generates_fluid_typography_values() {
 
 		// Results also include root site blocks styles.
 		$this->assertSame(
-			'body{--wp--preset--font-size--pickles: clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.156), 16px);--wp--preset--font-size--toast: clamp(14.642px, 0.915rem + ((1vw - 3.2px) * 0.575), 22px);}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(.is-layout-flex){gap: 0.5em;}:where(.is-layout-grid){gap: 0.5em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}body{font-size: clamp(0.875em, 0.875rem + ((1vw - 0.2em) * 0.156), 1em);}h1{font-size: clamp(50.171px, 3.136rem + ((1vw - 3.2px) * 3.893), 100px);}.wp-block-test-clamp-me{font-size: clamp(27.894px, 1.743rem + ((1vw - 3.2px) * 1.571), 48px);}.has-pickles-font-size{font-size: var(--wp--preset--font-size--pickles) !important;}.has-toast-font-size{font-size: var(--wp--preset--font-size--toast) !important;}',
+			':root{--wp--preset--font-size--pickles: clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.156), 16px);--wp--preset--font-size--toast: clamp(14.642px, 0.915rem + ((1vw - 3.2px) * 0.575), 22px);}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(.is-layout-flex){gap: 0.5em;}:where(.is-layout-grid){gap: 0.5em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}body{font-size: clamp(0.875em, 0.875rem + ((1vw - 0.2em) * 0.156), 1em);}h1{font-size: clamp(50.171px, 3.136rem + ((1vw - 3.2px) * 3.893), 100px);}.wp-block-test-clamp-me{font-size: clamp(27.894px, 1.743rem + ((1vw - 3.2px) * 1.571), 48px);}.has-pickles-font-size{font-size: var(--wp--preset--font-size--pickles) !important;}.has-toast-font-size{font-size: var(--wp--preset--font-size--toast) !important;}',
 			$theme_json->get_stylesheet()
 		);
 	}
@@ -3734,7 +3734,7 @@ public function test_get_styles_for_block_with_content_width() {
 			'selector' => 'body',
 		);
 
-		$expected    = 'body { margin: 0;--wp--style--global--content-size: 800px;--wp--style--global--wide-size: 1000px; }.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(.is-layout-flex){gap: 0.5em;}:where(.is-layout-grid){gap: 0.5em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}';
+		$expected    = ':root { --wp--style--global--content-size: 800px;--wp--style--global--wide-size: 1000px; }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(.is-layout-flex){gap: 0.5em;}:where(.is-layout-grid){gap: 0.5em;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}';
 		$root_rules  = $theme_json->get_root_layout_rules( WP_Theme_JSON_Gutenberg::ROOT_BLOCK_SELECTOR, $metadata );
 		$style_rules = $theme_json->get_styles_for_block( $metadata );
 		$this->assertSame( $expected, $root_rules . $style_rules );
@@ -3755,7 +3755,7 @@ public function test_get_styles_with_appearance_tools() {
 			'selector' => 'body',
 		);
 
-		$expected   = '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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }body { --wp--style--block-gap: ; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1;}:where(body .is-layout-grid) {gap: 1;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}';
+		$expected   = '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:first-child { margin-block-start: 0; }:where(.wp-site-blocks) > :last-child:last-child { margin-block-end: 0; }:root { --wp--style--block-gap: ; }:where(body .is-layout-flow)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-flow)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-flow)  > *{margin-block-start: 1;margin-block-end: 0;}:where(body .is-layout-constrained)  > :first-child:first-child{margin-block-start: 0;}:where(body .is-layout-constrained)  > :last-child:last-child{margin-block-end: 0;}:where(body .is-layout-constrained)  > *{margin-block-start: 1;margin-block-end: 0;}:where(body .is-layout-flex) {gap: 1;}:where(body .is-layout-grid) {gap: 1;}body .is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}body .is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}body .is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}body .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;}body .is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}body .is-layout-flex{flex-wrap: wrap;align-items: center;}body .is-layout-flex > *{margin: 0;}body .is-layout-grid{display: grid;}body .is-layout-grid > *{margin: 0;}';
 		$root_rules = $theme_json->get_root_layout_rules( WP_Theme_JSON_Gutenberg::ROOT_BLOCK_SELECTOR, $metadata );
 		$this->assertSame( $expected, $root_rules );
 	}
@@ -4750,7 +4750,7 @@ public function test_shadow_preset_styles() {
 			)
 		);
 
-		$expected_styles = 'body{--wp--preset--shadow--natural: 5px 5px 5px 0 black;--wp--preset--shadow--sharp: 5px 5px black;}';
+		$expected_styles = ':root{--wp--preset--shadow--natural: 5px 5px 5px 0 black;--wp--preset--shadow--sharp: 5px 5px black;}';
 		$this->assertSame( $expected_styles, $theme_json->get_stylesheet(), 'Styles returned from "::get_stylesheet()" does not match expectations' );
 		$this->assertSame( $expected_styles, $theme_json->get_stylesheet( array( 'variables' ) ), 'Styles returned from "::get_stylesheet()" when requiring "variables" type does not match expectations' );
 	}
@@ -4787,7 +4787,7 @@ public function test_get_shadow_styles_for_blocks() {
 			)
 		);
 
-		$global_styles   = 'body{--wp--preset--shadow--natural: 5px 5px 0 0 black;}' . static::$base_styles;
+		$global_styles   = ':root{--wp--preset--shadow--natural: 5px 5px 0 0 black;}' . static::$base_styles;
 		$element_styles  = 'a:where(:not(.wp-element-button)){box-shadow: var(--wp--preset--shadow--natural);}.wp-element-button, .wp-block-button__link{box-shadow: var(--wp--preset--shadow--natural);}p{box-shadow: var(--wp--preset--shadow--natural);}';
 		$expected_styles = $global_styles . $element_styles;
 		$this->assertSame( $expected_styles, $theme_json->get_stylesheet() );