Hello Ciatronical
For example you should use:
User-agent: *
Disallow: /system/
allow: /system/css
allow: /system/js
Disallow: /tmp/
allow: /tmp/*.js
allow: /tmp/*.css
Sitemap: https://_valid_domain.com_/sitemapindex.xml
User-agent: googlebot
Allow: /themes/
Allow: /system/js
Allow: /system/css
Regards, Pavel.