public function css(array $files, $outputFile)
    {
        if ($this->production) {
            return '<link rel="stylesheet" href="' . $outputFile . '">';
        }

        $this->minify($files, $outputFile, $this->cssMinifiers);

        $stylesheets = [];

        foreach ($files as $file) {
            $stylesheets[] = '<link rel="stylesheet" href="' . $file . '">';
        }

        return implode("\n", $stylesheets);
    }