Thanks for your feedback, ideas and kind words! Will check out Stephen Biesty's books. Unbelievable, you did a very well guess with the lemmings style. That's what I had in mind indeed! The other option that's in my head (and maybe we are closer to Mr. Biesty's books, here?) is not a game but an eLearning diaorama. Interacting with different parts of the mine is bringing up detailed informations - and could connect to certain actions needed (like a section: Ground water was a constant trouble, paired with interactively operating the pump - or: Dangerous coal gasses, paired with installing a ventilation) - I would have loved to learn with a thing like this when I was a child, I am pretty sure.