The game is easier once you are able mine all the blocks in one sack. The game will give you +120 money per sack, which is too much in my opinion.
But other than that, the game is perfect. It satisfies my dwarf greedness, mehehehe.. Didn't get the amethyst after a long time of playing though.
Would love to see further development of the game. Maybe we can build ballista or cannon. Good job, dev! Love your game.