public static function generate_popup_styles() {
		$popup_css = '';

		$popups = pum_get_all_popups();

		if ( ! empty( $popups ) ) {

			foreach ( $popups as $popup ) {
				// Set this popup as the global $current.
				pum()->current_popup = $popup;

				// Preprocess the content for shortcodes that need to enqueue their own assets.
				// PUM_Helpers::do_shortcode( $popup->post_content );

				$popup = pum_get_popup( $popup->ID );

				if ( ! pum_is_popup( $popup ) ) {
					continue;
				}

				ob_start();

				if ( $popup->get_setting( 'zindex', false ) ) {
					$zindex = absint( $popup->get_setting( 'zindex' ) );
					echo "#pum-{$popup->ID} {z-index: $zindex}\r\n";
				}

				// Allow per popup CSS additions.
				do_action( 'pum_generate_popup_css', $popup->ID );

				$popup_css .= ob_get_clean();

			}

			// Clear the global $current.
			pum()->current_popup = null;

		}

		return $popup_css;
	}