[markild]

I'm not entirely sure what you are saying, but I actually find this puzzle quite interesting.

(O|RM|HHM)* doesn't match "anything", but rather "nothing" or something quite specific. [0]

There are multiple rows in the puzzle where things _can_ match anything, but they are pretty fast limited by the opposing row/column.

[0]: http://www.regexper.com/#%28O|RM|HHM%29*

[leeoniya]

yeah sorry, wrote that in a hurry. i meant, if it can match nothing and still be valid, what's the point? you may as well write `.*`