Wonderful graphics (I might even be jealous because they are not in my game :) ) and the idea and implementation feel are awesome!
However, the lack of a "game feel" made me feel a little bit empty. For example, there are no animations for mining, upgrading, changing ores to coins, and attacking enemies. Also, when I tried to get out of the borders of the game, it glitched a little bit.
In short, I loved your game (literally) and it was fun to play. The only drawback was the absence of a game feel.