An asteroid of 5,000,000 m³ will hit Earth in 90 days. The UN Security Council already spent 90 days arguing about who pays. Then one miner came to the tender with his own pickaxe. He asked for no money and said the asteroid would pay for itself. The vote was unanimous, for the first time in history.
You are that miner. Every day you fly down and dig while your air lasts. Back on the ship you sell the ore and buy bigger tools and guns. A big counter shows how many m³ are left. On the first day it hardly moves. Later your ship fires at the rock while you dig, and the number goes down much faster.
From a pickaxe to a missile swarm
You start with the pickaxe you brought. The last tool is a swarm of small homing missiles. Big pieces break off and float away, and you can ride them.
The ship shoots too
Earth has rockets that are already paid for, but they are aimed at the neighbors. So your ship starts with no guns, and you buy them with the ore money. They fire at the asteroid on their own. The most expensive one shoots a black hole into the rock.
Earth is watching
What you find in the rock goes to the ship's museum, like an empty safe labeled "Asteroid defense budget". From the observation dome you can see Earth through a telescope. A crowd holds KEEP WORKING signs. Bookmakers take bets on you. The Security Council meets on a beach. The plot at the impact point is already sold, and the owners rave about the sky view.
Other clients
After the main contract, other clients send offers. A space hotel wants a duck-shaped asteroid gone, because guests say it keeps staring at them.
Singleplayer. The main contract takes about 6 to 9 hours.