You mentioned in another comment, that the crawler movement fits with the mining and I can second that. Maybe improve a bit on the controls, faster movement (only if not mining) and maybe move directly, when pressing a button and not, after you let it go. The graphics are fine and I had to think for a moment, how you implemnted the walls fitting together at all, very nicely done!
Just add some different ores and maybe have some poisenous zones or whatever and it could become something really nice.