your code
shuttle(50,50,2000);
mothership(600,700);
fuel(400,100,1000);
fuel(100,400,1000);
planet(200,100,'earth');
planet(500,300,'mars');
planet(200,400,'venus');
planet(400,600,'neptune');
planet(600,500,'mercury');
planet(100,700,'uranus');
planet(700,200,'jupiter');
asteroid(300,250);
asteroid(600,100);
wall(400,400,600,400);
alien(200,450,200,750);