build on it
could be the welcome start of something fresh in defence games. i would like to see the game take a more active approach to strategy, not just the usual "place your buildings and wait" kind of passive gameplay. by making mined resources more important you would demand of the player a more aggresive, proactive beahviour, as he wouldn't be able to rely on a fixed supply. Maybe make it so that you have to mine your way to resources and then keep the routes open for peons delivering the gold. Also, the forces of good and the game could benefit from digger units, and the player respond by hunting these down and sending peons to block those open passages with walls.