Revert "Use ponyfill instead of postcss to address IE."

This reverts commit d361c1a.

assets/sass/style.scss

@@ -17,7 +17,6 @@
  * Vertical-margins.....Vertical spacing for the main components.
  * Reset................Reset specific elements to make them easier to style in other contexts.
  * Clearings............Clearnings for the main components.
- * IE11.................Add the ponyfill for IE11.
  *
  * ELEMENTS
  * Blockquote...........Default blockquote.
@@ -91,7 +90,6 @@
 @import "03-generic/vertical-margins";
 @import "03-generic/reset";
 @import "03-generic/clearings";
-@import "03-generic/ie11";
 
 /* Category 04 can contain any default HTML element. Do not add classes here, just give the elements some basic styles. */
 @import "04-elements/blockquote";

functions.php

@@ -113,8 +113,17 @@ function twenty_twenty_one_setup() {
 		// Add support for editor styles.
 		add_theme_support( 'editor-styles' );
 
+		$editor_stylesheet_path = './assets/css/style-editor.css';
+
+		// Note, the is_IE global variable is defined by WordPress and is used
+		// to detect if the current browser is internet explorer.
+		global $is_IE;
+		if ( $is_IE ) {
+			$editor_stylesheet_path = './assets/css/ie-editor.css';
+		}
+
 		// Enqueue editor styles.
-		add_editor_style( './assets/css/style-editor.css' );
+		add_editor_style( $editor_stylesheet_path );
 
 		// Add custom editor font sizes.
 		add_theme_support(
@@ -317,8 +326,16 @@ function twenty_twenty_one_content_width() {
  * Enqueue scripts and styles.
  */
 function twenty_twenty_one_scripts() {
-	// Theme styles.
-	wp_enqueue_style( 'twenty-twenty-one-style', get_template_directory_uri() . '/style.css', array(), wp_get_theme()->get( 'Version' ) );
+	// Note, the is_IE global variable is defined by WordPress and is used
+	// to detect if the current browser is internet explorer.
+	global $is_IE;
+	if ( $is_IE ) {
+		// If IE 11 or below, use a flattened stylesheet with static values replacing CSS Variables.
+		wp_enqueue_style( 'twenty-twenty-one-style', get_template_directory_uri() . '/assets/css/ie.css', array(), wp_get_theme()->get( 'Version' ) );
+	} else {
+		// If not IE, use the standard stylesheet.
+		wp_enqueue_style( 'twenty-twenty-one-style', get_template_directory_uri() . '/style.css', array(), wp_get_theme()->get( 'Version' ) );
+	}
 
 	// RTL styles.
 	wp_style_add_data( 'twenty-twenty-one-style', 'rtl', 'replace' );
@@ -335,15 +352,6 @@ function twenty_twenty_one_scripts() {
 	if ( has_nav_menu( 'primary' ) ) {
 		wp_enqueue_script( 'twenty-twenty-one-primary-navigation-script', get_template_directory_uri() . '/assets/js/primary-navigation.js', array(), wp_get_theme()->get( 'Version' ), true );
 	}
-
-	// Note, the is_IE global variable is defined by WordPress and is used
-	// to detect if the current browser is internet explorer.
-	global $is_IE;
-	if ( $is_IE ) {
-		// If IE 11 or below, use a ponyfill to add CSS Variable support.
-		wp_register_script( 'css-vars-ponyfill', get_stylesheet_directory_uri() . '/assets/js/css-vars-ponyfill2.js', array(), wp_get_theme()->get( 'Version' ), true );
-		wp_enqueue_script( 'ie11-fix', get_template_directory_uri() . '/assets/js/ie11-fix.js', array( 'css-vars-ponyfill' ), wp_get_theme()->get( 'Version' ), true );
-	}
 }
 add_action( 'wp_enqueue_scripts', 'twenty_twenty_one_scripts' );