Miner, Dig It All

Your drill has one tank of fuel. See how deep the pit lets you get! Drag to lay a line of dynamite, fire it, then hold the drill to grind the shattered rock away. Clear the layer and it collapses under you, straight into a richer one. On the surface, sell the ore and buy a harder bit, wider blasts and a robot crew, then dive again. Ten layers down sits the lava core: crack it and the whole pit starts over, permanently richer!