With the Disallow: lines in robots.txt one disallows all pathname
strings starting with the specified string. If you want to allow / but
disallow /..*, you may list all your top-level files and directories:
User-agent: *
Disallow: /xyz.html
Disallow: /sales
...
which you have to update any time you add new files/dirs, or you
could disallow all files by their first letter and list all possible
filename starting letters, so you do not have to maintain robots.txt
too often:
User-agent: *
Disallow: /a
Disallow: /b
Disallow: /c
Disallow: /d
...
Disallow: /z