Nice little game :D The concept is clear, it works well! My high score is 552 so far o/
It's a bit frustrating to get out of drill so quickly, though. Maybe 1 iron could make more than 1 drill? Because at the moment, it seems to me that the best strategy is to press space until you arrive somewhere with a lot of resources just around you. But maybe you it's what you wanted?
Congratulation for this game! :D