public static function register_styles() {
		self::$styles_registered = true;

		if ( PUM_AssetCache::enabled() && false !== self::$cache_url ) {
			$cached = get_option( 'pum-has-cached-css' );

			if ( ! $cached || self::$debug ) {
				PUM_AssetCache::cache_css();
				$cached = get_option( 'pum-has-cached-css' );
			}

			wp_register_style( 'popup-maker-site', self::$cache_url . '/' . PUM_AssetCache::generate_cache_filename( 'pum-site-styles' ) . '.css?generated=' . $cached, array(), Popup_Maker::$VER );
		} else {
			wp_register_style( 'popup-maker-site', self::$css_url . 'pum-site' . ( is_rtl() ? '-rtl' : '' ) . self::$suffix . '.css', array(), Popup_Maker::$VER );
			self::inline_styles();
		}
	}