public function card_css( $selector = '.wc-credit-card-form-card-number' ) {
		$css = <<<CSS
{$selector}{
    background-repeat: no-repeat;
    background-position: right .6180469716em center;
    background-size: 31px 20px;
}
CSS;
		foreach ( $this->card_icons() as $icon => $url ) {
			$css .= <<<CSS

{$selector}.{$icon} {
	background-image: url("{$url}");
}
CSS;
		}
		return sprintf( '<style type="text/css">%s</style>', $css );

	}