Dig deep. Haul ore. Get rich.
Run a mountain mine of helmet-lamp moles: dig fifteen shafts from Coal to Starstone, hire Foremen so it runs while you are away, then move across eight mountains (and beyond) for Gold Stamps and forever-upgrades in the Workshop. Ring the Gold Rush bell, dig out cave-ins, dress your crew, play the Daily Dig and race the 3-minute Rush Shift leaderboard.
Grow a tiny mine into a mountain-deep empire: your mole crews dig ore in each shaft, the lift brings it up and the cart sells it at the depot, and the slowest of the three sets your income. Tap a tunnel, the lift or the cart to work it, hire Foremen so stations run by themselves even while you are away, tap level badges to upgrade, and open 12 shafts to move to a richer mountain for Gold Stamps that buy permanent Workshop upgrades. Tap mine events like the Gold Rush bell and cave-ins, finish daily tasks for shop gems, and race the 3-minute Rush Shift for the leaderboard.