public void move(int distance, Direction direction, boolean useFuel) {
		switch(direction) {
		case UP:
			location.y -= distance; break;
		case DOWN:
			location.y += distance; break;
		case LEFT: 
			location.x -= distance; break;
		case RIGHT:
			location.x += distance; break;
		default:
			assert false: "Bad direction: " + location;
		}
		if(useFuel) tank.useFuel(1);
	}