Iterate through ASCII pins.
More guesses about unicode characters in the PIN.
Add dictionary and incremental search.

Dictionary search is all 4-character words from
/usr/share/dict/american-english-large with all possible combinations
of capitalization.  Statically generated by a short python script and
then compiled into the binary.

The incremental search gradually expands the search character set, so
that we look at all punctuation passwords, then all passwords with
punctuation and numbers, then all passwords with punctuation, numbers,
and letters, then move on to unicode, etc.
Search variations on 'doge' as the password.
Skip all-numeric passwords during incremental search.