> Does that mean that these puzzles don't have a single answer each like Sudoku???
It seems like it uses the regex to check if your answer triggers to regular expression.
I too have never been good at #RegEx. This crossword and a game I found on fdroid are giving me a lot of great practice.
That puzzle through me off as well. `AB*` says "give me 'A' and then 'B' zero or more times.
(Click "help" for a reference)