
Actual gameplay
Tap to dig, then let the drills dig
Every tap chips the rock under your bit. Break a block and you drop deeper, through topsoil, clay and sandstone into iron, basalt and magma, where one block is worth more than a whole shift near the surface. Buy drills and they keep working while you are gone. Mind the heat down there: let it max out and the whole shaft stalls until it cools.