I'd recommend some form of upgrade system, otherwise it's just attempting high scores. A lot of people don't care about getting high scores, and those that do expect a leaderboard generally.
I'd also say it's a bit odd to have the side to side digging (pickaxe) relegated to a separate button. It would feel more natural to have it tied to a,d/left right arrow keys.
I appreciate that the game scrolls back up so you can see your work at the end, and that you chuck the treasure out as bars with actual physics to them. Fun times.