static function filterDefaults( $defaults ) {

		// SASS => WP
		$overrides = [
			'body-font-size' => 'pdf_body_font_size',
			'body-line-height' => 'pdf_body_line_height',
			'page-margin-top' => 'pdf_page_margin_top',
			'page-margin-inside' => 'pdf_page_margin_inside',
			'page-margin-bottom' => 'pdf_page_margin_bottom',
			'page-margin-outside' => 'pdf_page_margin_outside',
			'front-matter-running-content-left' => 'running_content_front_matter_left',
			'front-matter-running-content-right' => 'running_content_front_matter_right',
			'introduction-running-content-left' => 'running_content_introduction_left',
			'introduction-running-content-right' => 'running_content_introduction_right',
			'part-running-content-left' => 'running_content_part_left',
			'part-running-content-right' => 'running_content_part_right',
			'chapter-running-content-left' => 'running_content_chapter_left',
			'chapter-running-content-right' => 'running_content_chapter_right',
			'back-matter-running-content-left' => 'running_content_back_matter_left',
			'back-matter-running-content-right' => 'running_content_back_matter_right',
		];

		$transient_name = 'pressbooks_theme_options_pdf_parsed_sass_variables';
		$parsed_sass_variables = get_transient( $transient_name );
		if ( $parsed_sass_variables === false ) {
			// Order of files matter. If a variable is duplicated in other files then the last one takes precedence
			$parsed_sass_variables = [];
			$sass = Container::get( 'Sass' );
			$path_to_global = $sass->pathToGlobals();
			$path_to_theme = get_stylesheet_directory();
			$files = [
				$path_to_global . '/variables/_elements.scss',
				$path_to_global . '/variables/_structure.scss',
				$path_to_theme . '/assets/styles/components/_elements.scss',
				$path_to_theme . '/assets/styles/components/_structure.scss',
			];
			foreach ( $files as $file ) {
				if ( file_exists( $file ) ) {
					$parsed_sass_variables[] = $sass->parseVariables( \Pressbooks\Utility\get_contents( $file ) );
				}
			}
			set_transient( $transient_name, $parsed_sass_variables );
		}

		foreach ( $parsed_sass_variables as $parsed_variables ) {
			foreach ( $overrides as $sass_var => $wp_option ) {
				if ( isset( $parsed_variables[ $sass_var ] ) ) {
					$val = self::parseSassValue( $parsed_variables[ $sass_var ] );
					if ( ! empty( $val ) ) {
						if ( in_array( $wp_option, self::getFloatOptions(), true ) ) {
							$val = (float) preg_replace( '/[^0-9.]/', '', $val ); // Extract digits and periods
						} elseif ( in_array( $wp_option, self::getIntegerOptions(), true ) ) {
							$val = (int) preg_replace( '/[^0-9]/', '', $val ); // Extract digits
						} elseif ( in_array( $wp_option, self::getBooleanOptions(), true ) ) {
							$val = filter_var( $val, FILTER_VALIDATE_BOOLEAN ); // Convert to boolean
						} elseif ( strpos( $wp_option, 'running_content', true ) ) {
							$val = self::replaceRunningContentStrings( $val );
						}
						$defaults[ $wp_option ] = $val; // Override default with new value
					}
				}
			}
		}

		return $defaults;
	}