Yeah, we wanted it to be somewhat hard, and even with golden tier of the tools it woul be somewhat hard later on when you have access to deeper dig sites. You have to plow through top layers to get to the sweet-sweet old artifacts :) In full version of the game, with 12 eras, last level is 24 tiles deep and goes through 8 eras :) In this version, that fit deadline, 5th level is 9 tiles deep with 3 tiles per era