your code
shuttle(300,500,600);
mothership(600,200);
planet(500,350,"mars");
fuel(500,700,200);
planet(400,210,"earth");
planet(650,500,"jupiter");
wall(250,600,600,600);
alien(200,100,200,400);
fuel(600,350,400);
alien(100,400,300,400);
alien(500,0,500,800);
fuel(400,250,150);