Cool little game. Great art and music and good take on the theme. Just some critiques and suggestions:
The movement should have been grid based (move one unit each time) I ran into issues were one character wouldn't move far enough then get stuck
I also ran into issues were they would either dig on their own, or wouldn't dig at all then all of a sudden start digging on their own (made keeping track of the little guys tough)
Overall, really cool game though!