The game requires incentive. As far as I can tell, there is no actual reason to accrue score, and there's no punishment for doing nothing. I think that's the next step after developing the basic mechanics, which you do have.

I think some more gameplay is needed for sure, as it's quite simple and there isn't much of a challenge aspect other than not clicking on the red. The graphisc and sound designed complement each other very well, nice little mining game.