You start with one room, five metres square, adrift among the asteroids.

Open the blueprint and the ship becomes something you build. Add compartments cell by cell and the hull plating, the wall panels and the windows are raised around them. Cut a ladder well and you have a second deck. Bolt a rocket booster to an outside wall and it fires away from whatever it is planted on.

Then walk to the control console and fly it. The throttle is a lever from nought to full, the pad steers left, right, up and down, and a hologram of your own ship turns above the desk — your compartments, your engines, the deck you are standing on. Rocks pass the windows and the ones you hit push back.

There is no score and nothing chasing you. It is a ship, and it is yours to extend and to take somewhere.