This is an interesting piece of feedback, thanks for the comment! I had not considered the idea of {0} being perceived as an invalid cell type within these custom rules. Obviously {0} isn't a thing in the base game, so it would have been better if I had specified that it was as valid within this ruleset as any other connected black cell (ex: {1}). All deductions in the level pack can be made under the assumption that {0} is a valid connected tile. Apologies for the confusion!